Similar Histology Research Articles

Abstract A005: Canine hemangiosarcoma as a model for RAS-mutated human cancers: Preliminary data

Abstract Canine cancer patients represent an important translational model for human cancer research with their spontaneous tumor pathogenesis and the many histological, genetic, molecular and clinical similarities between canine and human tumors. Canine tumors provide an opportunity to investigate shared biomarkers and their response to therapeutic interventions over an accelerated timeline compared to human cancers due to differences in expected lifespan and other factors. Dogs, like humans, have three related RAS genes, HRAS, KRAS, and NRAS, with extremely similar genetic sequence and resultantly high protein homology. These proteins have many key molecular functions including roles in cell proliferation and survival. Across multiple human cancer types, recurrent gain-of-function missense mutations in the RAS-family genes occur primarily at codons 12, 13, and 61. These mutations result in constitutively active RAS proteins. The frequencies of mutations across the three RAS genes and codons have been hypothesized to lead to distinct biological behaviors. Mutations are most common in KRAS, then NRAS followed by HRAS. We investigated RAS-family genetic mutations in a dataset of 213 canine patients with hemangiosarcoma (HSA), a common, aggressive malignancy derived from endothelial cells for which treatment with both surgery and traditional chemotherapies often fail to prolong survival beyond six months. Recent publications show that genomic profiling of canine HSA tumors can help group tumors into subtypes with potential for guiding therapy selection and improving outcomes. All 213 dogs had tumor tissue sequenced via the FidoCure® Precision Medicine Platform targeted sequencing panel and were followed until time of death or were censored to the date patients were last known to be living. All SNVs and Indels detected were missense mutations. Unlike human pan-cancer data, somatic mutations in NRAS (n=32) were most common with only 1 dog with a somatic KRAS mutation and no dogs with somatic HRAS mutations. Similar to human RAS mutations, affected codons were primarily codon 61 (n=28), codon 13 (n=5), and codon 12 (n=1). Pairwise survival comparisons between dogs with missense mutations in NRAS codon 61 showed that this mutation was associated with better prognosis (n=28, MST 251 [CI 213;327]) compared to dogs with missense mutations at other codons in the NRAS and KRAS genes (n=5, MST 66 [CI 64;NA], p=1.58E-05) and compared to dogs without missense mutations in the RAS family of genes (n=180, MST 123 [CI 100;149], p=0.036). These preliminary findings of similarities between canine and human tumors and associations between mutated codons and prognosis in our growing dataset create an important opportunity to accelerate cancer research, including clinical and biopharmaceutical studies, with great potential benefit to both dogs and humans. Citation Format: Michelle E. White, Garrett Harvey, Lucas Rodrigues, Chase Schwalbach, Dorothy Girimonte, Aubrey Miller, Abigail Hull, Lindsay Lambert, Christina Lopes, Gerald Post. Canine hemangiosarcoma as a model for RAS-mutated human cancers: Preliminary data [abstract]. In: Proceedings of the AACR Special Conference: Targeting RAS; 2023 Mar 5-8; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Res 2023;21(5_Suppl):Abstract nr A005.

Comparing Genomic Landscapes of Oral and Cutaneous Squamous Cell Carcinoma of the Head and Neck: Quest for Novel Diagnostic Markers

Squamous cell carcinoma is the most common head and neck malignancy arising from the oral mucosa and the skin. The histologic and immunohistochemical features of oral squamous cell carcinoma (OSCC) and head and neck cutaneous squamous cell carcinoma (HNcSCC) are similar, making it difficult to identify the primary site in cases of metastases. With the advent of immunotherapy, reliable distinction of OSCC and HNcSCC at metastatic sites has important treatment and prognostic implications. Here, we investigate and compare the genomic landscape of OSCC and HNcSCC to identify diagnostically useful biomarkers. Whole-genome sequencing data from 57 OSCC and 41 HNcSCC patients were obtained for tumor and matched normal samples. Tumor mutation burden (TMB), Catalogue of Somatic Mutations in Cancer (COSMIC) mutational signatures, frequent chromosomal alterations, somatic single nucleotide, and copy number variations were analyzed. The median TMB of 3.75 in primary OSCC was significantly lower (P < .001) than that of 147.51 mutations/Mb in primary HNcSCC. The COSMIC mutation signatures were significantly different (P < .001) between OSCC and HNcSCC. OSCC showed COSMIC single-base substitution (SBS) mutation signature 1 and AID/APOBEC activity–associated signature 2 and/or 13. All except 1 HNcSCC from hair-bearing scalp showed UV damage–associated COSMIC SBS mutation signature 7. Both OSCC and HNcSCC demonstrated a predominance of tumor suppressor gene mutations, predominantly TP53. The most frequently mutated oncogenes were PIK3CA and MUC4 in OSCC and HNcSCC, respectively. The metastases of OSCC and HNcSCC demonstrated TMB and COSMIC SBS mutation signatures similar to their primary counterparts. The combination of high TMB and UV signature in a metastatic keratinizing squamous cell carcinoma suggests HNcSCC as the primary site and may also facilitate decisions regarding immunotherapy. HNcSCC and OSCC show distinct genomic profiles despite histologic and immunohistochemical similarities. Their genomic characteristics may underlie differences in behavior and guide treatment decisions in recurrent and metastatic settings.

Mucous Gland Adenoma of the Lung: A Neoplastic Counterpart of Mucinous Bronchial Glands

Mucous gland adenoma (MGA) is a rare benign tumor that usually arises in the proximal airway and consists of mucus-secreting cells resembling bronchial glands. Here, we report 2 cases of MGAs and describe their morphologic, immunohistochemical, and molecular profiles in comparison with 19 pulmonary tumors of 5 other histologic types with mucinous cells (invasive mucinous adenocarcinoma, mucoepidermoid carcinoma, mixed squamous cell and glandular papilloma, bronchiolar adenoma/ciliated muconodular papillary tumor, and sialadenoma papilliferum). Two MGAs were found in 1 male patient and 1 female patient, located in the bronchus and trachea, respectively. One MGA was examined by RNA sequencing, and no putative driver mutations (including BRAF, KRAS, and AKT1 mutations) or gene fusions were identified. In another case of MGA, V600E mutations of BRAF and E17K mutations of AKT1 were not detected by allele-specific real-time PCR or digital PCR, respectively. However, a gene expression analysis revealed that the MGA presented a specific RNA expression profile with multiple genes enriched in the salivary gland. The gene expression of NKX3.1 was significantly higher in the MGA case in comparison to normal control lungs (P < .001). We then examined NKX3.1 immunohistochemistry for 2 MGAs and 19 tumors of 5 other histologic types. NKX3.1 was positive in MGA (2/2, 100%), whereas all constituent cells, including mucinous cells, were negative for NKX3.1 in other histologic types (0%, 0/19). In normal lung tissue, NKX3.1 was positive for mucinous acinar cells of the bronchial glands. In conclusion, the gene expression profile, taken together with the histologic similarity between MGA and bronchial glands, and the preferred location of the tumors (proximal airways with submucosal glands) suggest that MGA is a neoplastic counterpart of mucinous bronchial glands. NKX3.1 immunohistochemistry can be a sensitive and specific ancillary marker that distinguishes MGA from other histologic mimics.

Abstract 2509: Similar variant histology and immune cell infiltration in canine and human muscle-invasive bladder cancer

Abstract Introduction: Muscle-Invasive Bladder Cancer (MIBC) is associated with a poor overall survival rate. One important factor that contributes to poor treatment outcomes is the histologic heterogeneity of MIBC tumors, which limits the translational value of some rodent models. As opposed to mice, dogs with spontaneously occurring bladder cancer have been shown to present with similar clinical behavior as human MIBC. In addition, canines have an intact immune system, which could provide for an ideal pre-clinical study population to investigate the efficacy of immunotherapy. In this study, we evaluated canine MIBC tumor biopsies for their similarities to human MIBC with regards to histology and immune cell infiltration. Materials &amp; Methods: Nine canine MIBC tumor samples were provided by the ISU pathology service and evaluated by a human uropathologist. Canine MIBC tumors were phenotypically characterized using either immunofluorescence (IF) or RNA in situ hybridization (RNA-ISH), including CD44, KRT7 and FOXA1, as well as specific markers characterizing the immune cell infiltrate, such as CD163 (tumor-associated macrophages), CD8a (cytotoxic T-lymphocytes), PD-L1 (immune-checkpoint protein) and TGFβ2 (cancer-associated fibroblasts). Results: Histologically, all canine MIBCs were classified as invasive, high-grade urothelial carcinomas (UC) with identical morphology to human MIBC. Interestingly, previously described histological variants of human MIBC tumors were also observed within the canine MIBC samples, such as glandular differentiation in 3/9 canine MIBC samples; epithelial-mesenchymal transition with sarcomatoid differentiation 1/9, squamous differentiation in 2/9 and micropapillary carcinoma in 1/9, all of which have been associated with poor clinical outcomes in human patients. IF was strongly positive for KRT7, FOXA1 and CD44, and immune cell markers CD163 and TGFβ2. However, CD8a was only weakly expressed (5/9) or negative, and PD-L1 was only positive in 4/9 canine MIBC biopsies. Conclusions: Canine MIBC tumors showed significant heterogeneity with highly similar histological variant morphologies to those reported in humans with MIBC. Furthermore, phenotypic characterization of immune cell infiltrates and checkpoint proteins suggest that the tumors were typically immunologically “cold”. These data further establish the utility of the spontaneous canine model of MIBC for pre-clinical investigation of novel therapeutic drug candidates, including immunotherapies. Citation Format: Karin Allenspach, John Cheville, Hannah Wickham, Christopher Zdyrski, Vojtech Gabriel, Basant Ahmed, Mei-Jyun Ciou, Fabrice Lucien, Igor Frank, Olufemi Fasina, Pablo Pineyro, Johnathan P. Mochel. Similar variant histology and immune cell infiltration in canine and human muscle-invasive bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2509.

Abstract 129: Determine the genetic similarity of synchronous endometrial and ovarian cancers with variants in polyguanine sequences

Abstract Endometrial and ovarian cancers are both fearsome gynecological diseases with high mortality rates worldwide. Due to their histological similarity, it is still a clinical challenge to distinguish between double primary cancer (DPC) and metastasis cancer (MC) in synchronous endometrial and ovarian cancers in which the latter represents a poor prognostic outcome. Clinically, the standard procedure for examining DPC and MC relies on their morphology and histopathology; however, showing poor accuracy even under explicating criteria. Here, we attempt to utilize indel variants within polyguanine (polyG) sequences to generate genetic distances of synchronous endometrial and ovarian tumors to normal tissue in a patient and then calculate the correlation coefficient for them. Polyguanine sequences are hypermutable guanine repeats that acquire insertion or deletion at a high incident rate (mutation rate: ~10-6 - 10-4; ~1000 folds higher than unique sequence) and, therefore, could serve as a very rich resource for comparing the genetic similarity between samples. The correlation between selected clinical variables, e.g., disease-free survival and the described correlation coefficient is then calculated to test whether this protocol can serve as an optimal tool for distinguishing between DPC and MC. We have assembled a cohort of 39 patients with synchronous endometrial and ovarian cancers in which pathologists cannot determine the relationship between endometrial and ovarian cancer in 23 of them. Preliminarily, we have collected DNA from formalin-fixed paraffin-embedded (FFPE) specimens and completed polyG genotyping for four of them. Indel variants, both insertions and deletions, are rich in all cases indicating the approach is technically rigid for this purpose even with FFPE specimens. Subsequently, we evaluate the similarity between endometrial and ovarian cancer by calculating Spearman's correlation with the genetic distances obtained from polyG genotyping. As the result of preliminary cases, we observe the correlation coefficient spreading between -0.14 to 0.95, implying this methodology can determine the genetic similarity between endometrial and ovarian tumor in a case and, therefore, could be a potential tool to supplement the current observation-based approach in the clinic. Our next step is to correlate the correlation coefficients with meaningful clinical variables once we complete genotyping the entire cohort. We anticipate this approach could provide additional information to distinguish DPC and MC and therefore benefit the patients. Citation Format: Yu-Yi Huang, Pei-Chi Cheng, Ching Hsu, Yung-Ming Jeng, Lin-Hung Wei, Wei-Ting Hung. Determine the genetic similarity of synchronous endometrial and ovarian cancers with variants in polyguanine sequences [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 129.

Abstract 3855: Establishment and characterization of a panel of breast XPDX models representing innate or acquired resistance to trastuzumab deruxtecan (T-DXd)

Abstract Background: Trastuzumab deruxtecan (T-DXd) is an ADC consisting of an anti-HER2 antibody linked to a novel topoisomerase I inhibitor payload approved for T-DM1-refractory, HER2+ breast cancer (BC) and metastatic, recurrent HER2-low BC. While this therapy is effective in some patients, resistance often develops. To aid in developing new therapies for T-DXd-resistant BC and better understand potential resistance mechanisms, we established a panel of six breast XPDX models representing innate or acquired resistance to T-DXd. These models, designated ST4565C, ST4565D, STM148B, STM148C, STM148D, and ST4480B/EHR were developed and characterized for receptor expression, genomics, and drug sensitivities toward chemotherapies and targeted agents including T-DXd, T-DM1, and margetuximab. Methods: ST4565C/D was established from a patient with ER+/HER2+, metastatic BC who was T-DXd treatment naïve. ST4565C was collected post chemo- and HER2-targeted therapies; ST4565D was collected following eribulin/margetuximab. STM148B/C/D were established from a patient with ER-/HER2+ metastatic BC following trastuzumab, T-DM1, and eleven months of T-DXd. ST4480B/EHR was established by chronic in vivo T-DXd dosing to the parent ST4480B ER+/HER2+ model until resistance developed. Resulting models were passaged and receptor expression confirmed by IHC and genomic analyses, including WES and RNAseq, were performed to further characterize models. In vivo, models were tested with agents including: trastuzumab, T-DM1, and T-DXd; endpoints included tumor volume (TV) and time from treatment initiation (TTI) with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Tumor regression (%T/C=&amp;lt;0) versus Day 0 TV was also reported. Results: Models retained receptor expression and similar histology comparable with archival clinical or model samples. In vivo, all ST4565 and STM148 models were refractory to trastuzumab, T-DM1, and T-DXd up to 10 mg/kg weekly with an average %T/C of 75%. ST4480B/EHR showed similar resistance to trastuzumab and T-DM1 at 10 mg/kg, and T-DXd at 3 mg/kg; T-DXd tested at 3 mg/kg in the ST4480B parent model resulted in tumor regressions. Sequencing of ST4565C/D identified a novel fusion, MTAP/CDKN2A/B deletions and elevated expression of FGFR1 and CCND1. In STM148 models an AKAP8L-NOTCH3 fusion and PIK3CA and CCNE1 mutations were reported. ST4480B/EHR reported PIK3CAE545K and an ESR1-CCDC170 fusion identical to the parent model, but differential expression was noted in several genes in the RICTOR/TORC2 pathway. Conclusion: We established and characterized six breast XPDX models representing innate or acquired resistance to T-DXd. These models are valuable tools in understanding resistance mechanisms and in developing novel therapies for T-DXd-resistant patients. Citation Format: Maci DeBoer, Albert Paez, Johnnie Flores, Robyn Baeza, Alyssa Simonson, Jim Lund, Kyriakos Papadopoulos, Thomas Gribbin, Amy Lang, Gladys Rodriguez, Lorena Mozas, Lorena Gonzalez, Manish Sharma, Emiliano Calvo, Tatiana Hernandez, Michael J. Wick. Establishment and characterization of a panel of breast XPDX models representing innate or acquired resistance to trastuzumab deruxtecan (T-DXd). [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3855.

Abstract 990: Immune-suppressive tumor microenvironment leads to poor survival following curative intent surgical resection in soft-tissue sarcomas

Abstract Surgical resection of early stage soft-tissue sarcomas (STS) is a potentially curative treatment; however, many STS tumors will recur. Predicting recurrence and survival outcomes for patients with early stage STS remains a challenge. In this study, we identify prognostic biomarkers from clinical and transcriptomic data form a large set of early stage STS. Primary tumor samples from 69 subjects with STS were sequenced using the Tempus xT targeted DNA and whole transcriptome next-generation sequencing platforms. The most common histologies included were liposarcoma (n=22), gastrointestinal stromal tumor (n=19), and leiomyosarcoma (n=12). As expected, high-grade tumors were associated with decreased DFS and OS times while tumor histology was only correlated with OS. Single sample gene set enrichment analysis (ssGSEA) values for seven Hallmark genesets were correlated with both DFS and OS; including pro-tumor survival pathways (p53, Apoptosis, TNF-α via NF-κB), tumor proliferation pathways (MTORC1, MYC Targets, Mitotic Spindle), and UV Response signaling. These pathways are associated with tumor proliferation as well as an immunosuppressive tumor microenvironment (TME). To assess the TME of these tumors we estimated immune cell infiltration using CIBERSORTx. Of the 22 cell types accounted for by CIBERSORTx, only elevated infiltration of M2 Macrophages were associated with poor DFS and OS. To further determine TME activation we assessed the expression of 74 known immune response associated genes. Only PDCD1 (PD-1) was associated with reduced DFS and OS times. Clustering on the nine variables identified here to correlate with both DFS and OS revealed two distinct clusters demonstrating similar histologies. While histologies were similar across clusters, cluster 2 exclusively included high-grade tumors while cluster 1 was made up of 57.4% high-grade tumors. Sub-classifying cluster 1 into low and high-grade subgroups demonstrated a stepped biomarker expression pattern associated with both tumor grade and cluster membership. Using established TME genesets, high-grade tumors demonstrated higher tumor proliferative scores than low-grade tumors, while cluster 2 tumors demonstrated increased tumor associated macrophage signaling. In a multivariable model, cluster membership outperformed tumor grade and histology as the only significant predictor of DFS or OS. Taken together, while tumor grade is a strong predictor of clinical outcomes following surgical resection in STS, immunosuppressive signaling patters may help to identify patients at the highest risk. Citation Format: Nathan David Seligson, Yan W. Asmann, Tariq Almerey, Steven Attia, Sanjay P. Bagaria. Immune-suppressive tumor microenvironment leads to poor survival following curative intent surgical resection in soft-tissue sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 990.

Abstract 3869: Short or long-term treatment with CDK4/6 inhibitors in patients with ER+ breast cancer: characterization and comparative analysis of resistance in seventeen XPDX models

Abstract Background: Mechanisms of resistance to CDK4/6 inhibitors (CDK4/6i) have been well studied and several alterations identified including RB loss and altered expression of related genes including CCNE1, E2F4 and CDK6. However, whether duration of clinical treatment might elicit specific mechanism(s) of CDK4/6i resistance is unclear. To better understand if duration of clinical treatment correlates with unique resistance mechanisms, we established, characterized, and compared a panel of ER+ breast XPDX models from patients who benefitted then progressed on a CDK4/6i. Patients were separated into two groups by time to progression (TTP): those who responded up to twelve months (RES12) and patients with clinical response greater than one year (RES13+). Methods: Seventeen breast cancer XPDX models were analyzed, including eight previously described (7xRES12; 1xRES13+: SABCS2021: T Hernandez et al). Nine new models were established from seven patients: six from fluid samples with three designated as ductal (ST3105B, ST3105C, STM001B) and three lobular carcinoma (STM182, STM229, STM229B); two from lymph node biopsies (ST5676, STM127) and one from a liver core biopsy (ST4887B), all reported as ductal carcinoma. STM182 was classified as RES12 and the remaining eight as RES13+. These models were passaged and challenged with CDK4/6i to confirm resistance. Receptor expression was determined by IHC and genomic analyses including WES and RNAseq, were performed to identify mechanisms of resistance. For in vivo studies, CDK4/6i were dosed PO once daily at 50 mg/kg; endpoints included tumor volume (TV) and time from treatment initiation (TTI) with %T/C values and tumor regression reported at study completion; a %T/C of ≤20 versus control was considered sensitive. Tumor regression (%T/C&amp;lt;0) versus Day 0 TV was also reported. Results: Clinical TTP for RES12 (n=8) was four to twelve months and RES13+ (n=9) from thirteen to forty-two months. All models retained ER expression in evaluated passages with similar histology compared with archival clinical samples. Sequencing identified several variants including RB1 truncations or deletions and increased gene expression in CCND1, CCNE1 and the PIK3CA/AKT pathway. Interestingly, 5/8 RES12 models reported ESR1 mutations or fusions versus 1/9 RES13+ and PIK3CA mutations were reported in 1/8 RES12 versus 5/9 RES13+. Several RES13+ models also reported variants and increased amplification in the RICTOR/TORC2 pathway versus RES12. Conclusion: We have established, characterized, and compared a panel of seventeen breast XPDX models from fourteen female patients representing early or late acquired resistance to CDK4/6i therapy and identified potential differences in each set. These models and resulting data are useful in developing novel therapies for CDK4/6i-resistant patients. Citation Format: Alyssa Simonson, Johnnie Flores, Morgan Lynch, Emily Carpenter, Justine Hruzek, Jim Lund, Natalia Baños Herraiz, Kyriakos Papadopoulos, Amy Vander Woude, Gladys Rodriguez, Sreenivasa Chandana, Thomas Gribbin, Nehal Lakhani, Tatiana Hernandez, Maria Jose de Miguel, Amy Lang, Michael J. Wick. Short or long-term treatment with CDK4/6 inhibitors in patients with ER+ breast cancer: characterization and comparative analysis of resistance in seventeen XPDX models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3869.

Pseudolymphoma to Lymphoma: A Case of Chronic Reactive Lymphoid Hyperplasia Transforming to Primary Cutaneous Marginal Zone Lymphoma.

Primary cutaneous marginal zone lymphoma (PCMZL) is a low-grade malignant B-cell lymphoma that originates from the skin. It often presents as erythematous solitary or multiple papules, nodules, and/or plaques. It is one of the 3 main subtypes of primary cutaneous B-cell lymphomas. PCMZLs are believed to develop from chronic antigenic stimulation such as from tick-borne bacteria, vaccines, tattoo pigment, or other foreign body. In addition, cutaneous lymphoid hyperplasia, a documented precursor to malignant PCMZL, often presents in response to areas of chronic inflammation. Cutaneous lymphoid hyperplasia and PCMZL share several clinical and histological similarities that require clinicopathologic suspicion, immunohistochemical ancillary studies, and histopathologic analysis to accurately differentiate the 2 entities. Although gene rearrangement studies have historically been of limited value in the diagnosis of PCMZL, recent studies investigating molecular markers have identified the presence of multiple genetic abnormalities that have helped to better characterize the disease and aid in diagnosis. In addition, newer studies have found associations between PCMZL and gastrointestinal disorders, including Helicobacter pylori and inflammatory bowel disorders. In this article, we describe a case of a 56-year-old patient with a history of ulcerative colitis presenting with chronic reactive lymphoid hyperplasia that transformed to primary cutaneous marginal zone lymphoma.

340 Predicting Progression and Recurrence of Pediatric Low Grade Gliomas Using miRNA Composition in Plasma and CSF

INTRODUCTION: Liquid biopsy is a non-invasive method of diagnosing and monitoring brain tumor patients. miRNA profiling from cerebrospinal fluid (CSF) and plasma has become an increasingly attractive biomarker, however targets have yet to be established in CNS tumors. Low grade glioma (LGG) patients often have excellent outcomes, but some have progressive disease or unresectable lesions. There has been limited work in establishing a clinically approved liquid biopsy assay for such patients. METHODS: miRNA profiling of 17 plasma and 12 CSF samples from 10 pediatric LGG and 7 DMG patients was performed using the HTG EdgeSeq platform. Clinical information was obtained through chart review. miRNA expression was evaluated with unsupervised consensus clustering and differential analysis. RESULTS: At time of data analysis, 5 LGG had progression or recurrence. The remaining LGG (5) had stable or no evidence of disease. Mean follow-up was 23 months. miRNA consensus clustering revealed that LGG with a recurrence, progression, or malignant transformation clustered with DMG rather than with tumors of similar histology or WHO classification. Pilocytic astrocytoma could be identified by miRNA composition in CSF. In plasma, 103 unique miRNAs were identified with significant differential expression between the progression/recurrence LGG cohort versus those with stable or no evidence of disease (logFC &gt; 1, FDR &lt; 0.05). miR-16-5p, a miRNA correlated with tumor growth and invasion in non-CNS tumors, had higher expression in the more aggressive cohort (p = 0.0022). Over 100 miRNAs correlated with histology, survival, disease state, and presence of leptomeningeal disease (p &lt; 0.05). CONCLUSIONS: miRNA profiling of CSF and plasma in patients with LGG may predict disease course to better inform patient care and treatment monitoring.

Sarcoidosis, Mycobacterium paratuberculosis and Noncaseating Granulomas: Who Moved My Cheese.

Clinical and histological similarities between sarcoidosis and tuberculosis have driven repeated investigations looking for a mycobacterial cause of sarcoidosis. Over 50 years ago, "anonymous mycobacteria" were suggested to have a role in the etiology of sarcoidosis. Both tuberculosis and sarcoidosis have a predilection for lung involvement, though each can be found in any area of the body. A key histopathologic feature of both sarcoidosis and tuberculosis is the granuloma-while the tuberculous caseating granuloma has an area of caseous necrosis with a cheesy consistency; the non-caseating granuloma of sarcoidosis does not have this feature. This article reviews and reiterates the complicity of the infectious agent, Mycobacterium avium subsp. paratuberculosis (MAP) as a cause of sarcoidosis. MAP is involved in a parallel story as the putative cause of Crohn's disease, another disease featuring noncaseating granulomas. MAP is a zoonotic agent infecting ruminant animals and is found in dairy products and in environmental contamination of water and air. Despite increasing evidence tying MAP to several human diseases, there is a continued resistance to embracing its pleiotropic roles. "Who Moved My Cheese" is a simple yet powerful book that explores the ways in which individuals react to change. Extending the metaphor, the "non-cheesy" granuloma of sarcoidosis actually contains the difficult-to-detect "cheese", MAP; MAP did not move, it was there all along.

Update on Sinonasal Tract Malignancies: Advances in Diagnostic Modalities.

Sinonasal tract malignancies are rare cancers with frequent morphologic overlap. Given the similar histologic profiles seen in many of these entities, they often present a diagnostic challenge to the practicing pathologist. To provide a streamlined algorithm using histologic clues, immunohistochemical profiles, and molecular assays to aid in diagnosis of these lesions. Sources were the World Health Organization Tumor Classification, literature review, and institutional experience. Although many sinonasal tract malignancies show similar histology, distinct immunohistochemical and molecular profiles can help parse out differences, thereby facilitating diagnosis for the pathologist.

The Effects of Omega-3 Polyunsaturated Fatty Acids on Breast Cancer as a Preventive Measure or as an Adjunct to Conventional Treatments

In order to understand how omega-3 polyunsaturated fatty acid (ω-3 PUFA) supplements affect breast cancer prevention and treatment, a systematic review of articles published in the last 5 years in two databases was performed. Of the 679 articles identified, only 27 were included and examined based on five topics, taking into account: the induction type of the breast cancer used in animal models; the characteristics of the induction model by cell transplantation; the experimental design of the ω-3 supplementation-combined or not with a treatment antitumor drug; the fatty acids (FAs) composition used; the analysis of the studies' outcomes. There are diverse and well-established animal models of breast cancer in the literature, with very relevant histological and molecular similarities depending on the specific objective of the study, such as whether the method of tumor induction was transgenic, by cell transplantation, or by oncogenic drugs. The analyses of outcomes were mainly focused on monitoring tumor growth, body/tumor weight, and molecular, genetic, or histological analyses, and few studies evaluated latency, survival, or metastases. The best results occurred when supplementation with ω-3 PUFA was associated with antitumor drugs, especially in the analysis of metastases and volume/weight of tumors or when the supplementation was started early and maintained for a long time. However, the beneficial effect of ω-3 PUFA supplementation when not associated with an antitumor agent remains unclear.

Abstract P2-23-15: Histologic, immunohistochemical and genomic comparison between classic Invasive lobular carcinomas and lobular-like invasive ductal carcinomas

Abstract Background: Invasive lobular carcinomas (ILCs) are the most frequent special histologic subtype of breast cancer, accounting for up to 15% of all breast cancer cases. ILCs are characterized by a distinctive discohesive growth pattern, with cells arranged in single cell infiltrative file and dispersed throughout the stroma, which stems from the loss of E-cadherin expression due to bi-allelic inactivation of the CDH1 gene. A subset of breast cancers display a similar single cell infiltrative growth pattern but, in contrast to classic ILC, display diffuse strong membranous E-cadherin reactivity and membranous p120 expression. We refer to such cases as “lobular-like invasive ductal carcinoma” (LLIDC), but it is unclear if this terminology is appropriate and if such cases show biallelic inactivation of CDH1, similarly to ILCs. Here, we sought to define whether LLIDCs would harbor bi-allelic alterations of CDH1 and to perform an exploratory, hypothesis generating analysis of the repertoire of somatic genetic alterations of LLIDCs and classic ILCs. Materials and methods: Representative H&amp;Es, as well as sections subjected to E-cadherin and p120 immunohistochemistry from seven classic ILCs and seven bona fide “lobular-like invasive ductal carcinomas” were retrieved and independently reviewed by two pathologists with experience and expertise in breast pathology. DNA samples were extracted from representative sections from tumor and normal breast tissue from each patient and subjected to an FDA-approved targeted sequencing assay comprising the coding regions and selected regulatory elements of 515 genes. Somatic single nucleotide variants (SNVs) were detected with MuTect, indels with Strelka, Varscan2, Scalpel and Lancet. All mutations were manually inspected using the Integrative Genomics Viewer (IGV). The cancer cell fraction (CCF) of each mutation was inferred, as well as clonal probability, using ABSOLUTE. Copy number alterations and loss of heterozygosity were determined using FACETS. Mutational signatures were inferred using SigMA based on all synonymous and nonsynonymous somatic mutations. Results: Based on the histopathologic evaluation, of the 14 cases analyzed, seven were classified as ILC, and the other seven were classified as LLIDC. Sequencing analysis revealed that the classic ILCs harbored 16q LOH and CDH1 mutations (7/7), of which five were frameshift indel and two were splice site mutations consistently coupled with loss-of-heterozygosity (LOH) of the wild-type allele. Conversely, five of the seven LLIDCs did not harbor CDH1 mutations or genomic rearrangements. CDH1 mutations were identified in 2 LLIDCs: one harbored a subclonal CDH1 in-frame indel mutation coupled with LOH. This case displayed membranous E-cadherin and p120 expression with areas of aberrant expression. The other CDH1-mutated LLIDC harbored a complex in-frame indel with subclonal LOH. This case displayed membranous E-cadherin and p120 expression. The comparative analysis of the repertoire of somatic genetic alterations and mutational signatures present in LLIDCs and classic ILCs did not reveal any significant differences. Conclusion: Despite the histologic similarities, LLIDCs differ from classic lobular carcinomas based on the lack of CDH1 bi-allelic inactivation and the patterns of expression of E-cadherin and p120 catenin. Further whole-genome sequencing analyses are warranted to define the molecular basis of the discohesive cancer cells of LLIDC display. Citation Format: Edaise M. da Silva, Thais Basili, Jing Yu, Juan Blanco-Heredia, Pier Selenica, Qiqi Ye, Arnaud da Cruz Paula, Higinio Dopeso, Antonio Marra, Steffi Oesterreich, Jorge Reis-Filho, Rohit Bhargava. Histologic, immunohistochemical and genomic comparison between classic Invasive lobular carcinomas and lobular-like invasive ductal carcinomas [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-23-15.

Abstract P1-13-03: Establishment and characterization of two T-DM1-resistant, ER+/HER2+ breast XPDX models developed sequentially from the same patient with differential in vivo sensitivity to trastuzumab deruxtecan (DS-8201a)

Abstract Background: Trastuzumab deruxtecan (DS-8201a) is an antibody-drug conjugate (ADC), consisting of a humanized anti-HER2 (human epidermal growth factor receptor 2) monoclonal antibody linked to a topoisomerase I inhibitor payload using a cleavable tetrapeptide-based linker, approved for the treatment of HER2+ metastatic breast cancer patients refractory to anti-HER2 therapy including T-DM1. While some mechanisms for clinical T-DM1 resistance have been identified, less is known about innate or acquired resistance to DS-8201a. We established two XenoSTART Patient-Derived Xenograft (XPDX) models from tissue samples collected two years apart from a patient with ER+/HER2+ breast cancer before and after HER2 directed therapies. These models designated ST4565 and ST4565C were developed and characterized for receptor expression, genomic alterations, and in vivo drug sensitivities toward multiple chemotherapies and targeted agents, including T-DM1 and DS-8201a. Methods: Models ST4565 and ST4565C were established from breast samples collected from a Caucasian female with ER+/HER2+ metastatic breast cancer; ST4565 was collected at age 35 prior to therapy and ST4564C at age 37 following several treatment regimens including 5-FU/doxorubicin/cyclophosphamide, docetaxel/trastuzumab/pertuzumab, and T-DM1/anastrozole. Both were grown subcutaneously in female athymic nude mice supplemented with exogenous estradiol. The resulting models were passaged, and receptor expression confirmed immunohistochemically; genomic analysis, including WES and RNAseq, was performed to further characterize the models. For in vivo studies, both models were evaluated using several chemotherapy and targeted agents alone and in combination including: trastuzumab, pertuzumab, T-DM1, DS-8201a, neratinib, tucatinib, fulvestrant, alpelisib, sacituzumab, and irinotecan. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a T/C of ≤ 20% versus control was considered sensitive. Tumor regression (%T/C=&amp;lt; 0) versus Day 0 tumor volume was also reported. Results: ST4565 and ST4565C retained comparable receptor expression (ER=2+/HER2=3+) over tested passages with similar histology compared to archival clinical samples. DNA/RNA sequencing identified several conserved variants including loss of CDKN2A/B and MTAP and a CNV=14 for CCND1. In vivo, ST4565 and ST4565C were found resistant to T-DM1 at 3 mg/kg weekly with a T/C of 100% in both models. However, DS-8201a treatment at 3 mg/kg weekly resulted in partial tumor regressions in ST4565 (T/C=-51%) while ST4565C was found resistant (T/C=49%). Both models were found resistant to all tested chemotherapies and all other targeted therapies but reported similar sensitivity to fulvestrant (T/C=~40%). Conclusion: We established two XPDX models representing T-DM1-resistant, ER+/HER2+ breast cancer from breast samples collected two years apart from the same patient that were found differentially responsive to DS-8201a. These models can be utilized as a valuable tool in better understanding innate resistance to T-DM1 and acquired resistance to DS-8201a. Citation Format: George Plasko, Johnnie Flores, Alyssa Simonson, Peter Forofontov, Ashwin Varma, Amy Lang, Gladys Rodriguez, Kyriakos P. Papadopoulos, Drew Rasco, Amita Patnaik, Bruce Conway, Joe Johnston, Michael Wick. Establishment and characterization of two T-DM1-resistant, ER+/HER2+ breast XPDX models developed sequentially from the same patient with differential in vivo sensitivity to trastuzumab deruxtecan (DS-8201a) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-13-03.

Abstract P1-13-22: Establishment and characterization of two ER+/HER2- XPDX models developed sequentially before and after acquired resistance to the CDK4/6 inhibitor palbociclib from a patient with metastatic breast cancer

Abstract Background: Several CDK4/6 inhibitors have recently been approved in combination with letrozole or fulvestrant in hormone receptor-positive breast cancer. Although this combination therapy has been found effective in some patients, resistance often develops. To aid in developing new therapies for CDK4/6i-resistant breast cancer and better understand potential resistance mechanisms, we established two XenoSTART Patient-Derived Xenograft (XPDX) models representing ER+/HER2- breast cancer from tissue samples collected seventeen months apart from the same patient before and after palbociclib therapy. These models designated ST4887 and ST4887B were developed and characterized for receptor expression, genomic alterations, and in vivo drug sensitivities toward multiple chemotherapies and targeted agents, including CDK4/6i and fulvestrant. Methods: Models ST4887 and ST4887B were established from metastatic samples collected from a Caucasian female with ER+/HER2- metastatic breast cancer; ST4887 was collected at age 38 from a femur mass biopsy following several treatment regimens including paclitaxel/doxorubicin/cyclophosphamide, radiation and tamoxifen. ST4887B was collected at age 39 from a liver biopsy following treatment with palbociclib/letrozole then palbociclib/fulvestrant, and finally ixabepilone/capecitabine. Both were grown subcutaneously in female athymic nude mice supplemented with exogenous estradiol. The resulting models were passaged, and receptor expression confirmed immunohistochemically; genomic analysis, including WES and RNAseq, was performed to further characterize models. For in vivo studies, both models were evaluated using several chemotherapy and targeted agents alone and in combination including cisplatin, docetaxel, CDK4/6i, fulvestrant, letrozole, olaparib, niraparib, and sacituzumab. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a T/C of ≤ 20% versus control was considered sensitive. Tumor regression (%T/C=&amp;lt; 0) versus Day 0 tumor volume was also reported. Results: ST4887 and ST4887B retained comparable receptor expression (ER=3+/HER2=1+) over tested passages with similar histology compared to archival clinical samples. DNA/RNA sequencing identified several conserved variants including a somatic BRCA2 truncation (BRCA2Y2660*); transcriptomic analysis revealed upregulation of several related genes but no notable fusions. In vivo, both models were insensitive to cisplatin or docetaxel, however ST4887 but not ST4887B was sensitive to fulvestrant or CDK4/6i therapies, although abemaciclib demonstrated some activity toward ST4887B. PARP inhibitors were active toward ST4887 and to a lesser extent ST4887B, while sacituzumab did not have a significant effect on either model. Conclusion: We established and characterized two XPDX models from the same patient before and after acquired resistance to the CDK4/6i palbociclib. Both models were found to retain receptor status and drug sensitivities similar to the patient at the time of sample collection. These models can be utilized as a valuable tool in better understanding acquired resistance to palbociclib. Citation Format: Ashwin Varma, Johnnie Flores, Alyssa Simonson, Anna Stackpole, Kyriakos P. Papadopoulos, Amita Patnaik, Drew Rasco, Muralidhar Beeram, Marisa Sandera, Michael Wick. Establishment and characterization of two ER+/HER2- XPDX models developed sequentially before and after acquired resistance to the CDK4/6 inhibitor palbociclib from a patient with metastatic breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-13-22.

Novel Insights Into Immunohistochemical Analysis For Acinar Cell Neoplasm of The Pancreas: Carboxypeptidase A2, Carboxypeptidase A1, and Glycoprotein 2.

Acinar cell carcinoma (ACC) is a rare and highly malignant pancreatic tumor. Owing to histologic similarity, ACC is often difficult to distinguish from other solid medullary pancreatic tumors, particularly neuroendocrine neoplasm (NEN) and intraductal tubulopapillary neoplasm (ITPN). We aimed to identify new immunohistochemical markers commonly expressed in tumor cells with acinar cell differentiation and useful for both surgical and small biopsy specimens. Candidate molecules exclusively expressed in neoplastic or non-neoplastic acinar cells in pancreatic tissues with specific and available antibodies suitable for immunohistochemistry were selected. We selected carboxypeptidase A1 (CPA1), carboxypeptidase A2 (CPA2), and glycoprotein 2 (GP2), which were expressed in 100%, 100%, and 96% of cases, respectively, in ACC (n=27) or neoplasia with acinar cell differentiation, including mixed acinar-neuroendocrine carcinoma (n=9), mixed acinar-ductal carcinoma (n=3), pancreatoblastoma (n=4), and acinar cystic transformation (n=2), in the cytoplasm of tumor cells with a granular pattern. Both CPA2 and CPA1 were not expressed in any other tumors without acinar cell differentiation, including NEN (n=44), pancreatic ductal adenocarcinoma (n=44), and ITPN (n=4). GP2 was not expressed in these tumors except in rare cases, including 14% of NEN, 15% of intraductal papillary-mucinous neoplasm, 25% of intraductal oncocytic papillary neoplasm, 25% of ITPN, and 7% of pancreatic ductal adenocarcinoma, wherein a small proportion of tumor cells expressed GP2 in their apical cell membrane. NEN cases also showed cytoplasmic GP2 expression. Therefore, CPA2, CPA1, and potentially GP2 may act as ACC markers.

Atezolizumab with platinum and etoposide chemotherapy followed by cystectomy for patients with localized small cell neuroendocrine bladder cancer.

TPS599 Background: Small cell bladder cancer (SCBC) is a rare aggressive bladder cancer (BC) variant comprising &lt;1% of BC. Recommended front line etoposide and platinum chemotherapy for SCBC is extrapolated from small cell lung cancer (SCLCA) studies. Data describing small cell bladder cancer treatment are predominantly retrospective. Substitution of etoposide for gemcitabine with cis or carboplatin is widely accepted. This extrapolation is based on histologic similarity between the rare SCBC, and more common SCLCA. Recently, several teams have shown DNA mutation patterns are also more consistent between SCBC and SCLCA, compared to SCBC and urothelial bladder cancers, further supporting the divergence in treatment. These patterns which characterize this “neuronal” subgroup in the TCGA dataset, also reinforce this group has the poorest OS outcome vs other subtypes. Patients with SCBC are nearly uniformly excluded from BC trials, and thus the response to checkpoint inhibition and other novel therapies in SCBC is unknown. As SCBCs often respond to, then quickly recur post chemotherapy, novel active therapies are needed. Immune checkpoint blockade with anti-PD(L)1 antibodies is clinically active, leading to objective responses in approximately 15-25% of patients with urothelial cancer, and 33% in biomarker selected patients with SCLCA. In IMpower133, Atezolizumab + carboplatin + etoposide vs chemotherapy alone demonstrated significant OS advantage (12.3 vs 10.3 months) in frontline ES SCLCA, a practice changing milestone. Like urothelial bladder and SCLCA, we believe SCBC may have dramatic response to checkpoint inhibitors, as shown in small case series from our team and others. Methods: Patients with invasive (cT1-cT4) small cell/neuroendocrine carcinoma of the bladder (MIBC), with or without urothelial cancer component, who are eligible for radical cystectomy and platinum chemotherapy and immunotherapy will be enrolled. Patients with N1 disease within the true pelvis are eligible. Atezolizumab 1200 mg IV Day 1 of every 21 day cycle with etoposide and investigator choice cisplatin or carboplatin chemotherapy x 4 neoadjuvant cycles will be delivered. The primary objective is to assess pathologic complete response rate following protocol therapy. Following cystectomy, Atezolizumab maintenance Q 21 days will continue until unacceptable toxicity or loss of clinical benefit for up to 1 year (e.g., 16 cycles). With type I and type II error rates of 5 and 10% respectively, the first stage will consist of 15 patients. If 6 or fewer patients respond, the study will terminate after the first stage. Otherwise, accrual will continue to 34 patients. If 17 or fewer patients respond at the end of the second stage, the study will terminate after the second stage. If 18 or more patients respond, accrual will continue to 63 patients. Secondary endpoints include rates of DFS and OS. Clinical trial information: NCT05312671 .

Clear Cell Sarcoma of Soft Tissue: A Case Report

Introduction: Clear cell sarcoma (CCS), is an extremely rare type of sarcoma, frequently diagnosed in young adults, typically arises in the extremities of the limbs and has a predilection for occurring in the tendons and aponeuroses. In the past CCS was called malignant melanoma of the soft parts because the tumor shares clinical, histological and immunohistochemical similarities with amelanotic melanoma, but it is a unique lesion, distinct from melanoma. Case Report: A 33-year old woman with no significant history was referred with an unpainful bulky ulcerated tumor of the right ankle, appeared 05 years prior to presentation following a minimal trauma. The CT of the ankle revealed a bulky mass of the medial surface locally infiltrative associated to nodules of the surrounding adipose tissues and a unilamellar periosteal reaction without bone lysis or osteocondensation. MRI of the ankle showing a lobulated mass arising in the deep structures in iso-intense signal relative to adjacent muscle on T1 and heterogeneous high-signal intensity on T2 infiltrating surrounding adipose tissues without infiltration of muscles. Histological examination showed dermo-hypodermic malignant tumor proliferation. Round cells were arranged in nests separated by dense collagenous septa, with an abundant eosinophilic to clear cytoplasm. The immunohistochemical supplement were positive for Melan-A and HMB-45. Cytokeratin, Vimentin, Desmin and CD99 were negative. The extension assessment made of a head-chest-abdominal-pelvic CT scan showed multiple homolateral inguinal lymphadenopathies necrotic. No other metastasis was detected. The anatomo-clinical confrontation allowed to retain the diagnosis of CCS. Discussion: The tumor occurs most often in adolescents and young adults and was slightly more common in female than in male patients, CCS typically arises in the extremities of the limbs, its occurrence in the upper limbs is less common, described as a slowly growing mass painless. ..........

Verrucous epidermal nevi: some aspects of pathogenesis and clinical cases

Verrucous epidermal nevi ― hamartomas of keratinocyte or epidermal appendages, located on the skin or mucous membranes in the form of isolated birthmarks, less often have a linear localization. The pathogenesis of verrucous epidermal nevi has not been fully defined, probably the development of the disease is associated with genetic mutations during embryogenesis and represent a special form of skin mosaicism. Verrucous epidermal nevi are skin pathologies that require attention as potentially dangerous in terms of the development of malignant neoplasms of the skin and due to the possible difficulties in their diagnosis and differential diagnosis.&#x0D; Analysis of current data on the pathogenesis and differential diagnosis of various forms of verrucous epidermal nevi, presentation of clinical cases of verrucous epidermal nevi.&#x0D; The article considers two clinical cases of linear verrucous epidermal nevus. Studies of the pathogenesis of WEN have shown the presence of changes in expressed proteins by affected skin cells, such as OGN, NT5C3A, ADD1, OLFML1, DHRS1, CALML5, SAMHD1, SFRP2, SPRR1B and SERPINB13. This may indicate the participation in the development of verrucous epidermal nevi of changes in the p53 signaling pathway, the cellular response to a cytokine stimulus, and disturbances in cell adhesion and differentiation of Th1 and Th2 cells. The presented clinical cases describe linear verrucous epidermal nevus in order to study the diagnosis of the disease, based on the clinical picture. The need for differential diagnosis of various forms of verrucous epidermal nevi is due to their clinical and sometimes histological similarity with other skin formations. Immunohistochemical examination, genetic analysis using sequencing of the affected skin exome, and proteomic analysis of proteins expressed by affected skin cells help to carry out differential diagnosis.&#x0D; The study of the mechanisms of development of this disease will help not only in differential diagnosis with other skin diseases, but will also allow finding new approaches to its conservative therapy.