Myoepithelial Markers Research Articles

Sneaky DCIS-looking Invasive Ductal Carcinoma of the Breast in the Extensive DCIS Background

Abstract Introduction/Objective In the most cases, invasive ductal carcinoma (IDC) of the breast is identifiable when they present with classic infiltrative growth pattern. However, subset of IDC can occur in a very sneaky way, significantly mimicking the appearance of ductal carcinoma in situ (DCIS). In this condition, it’s much more easier to miss the invasive component without pulling ancillary staining when morphologic findings are extremely compatible with DCIS, especially the diagnosis of DCIS was made on the previous biopsy. Methods/Case Report Retrospective analysis of the histologic and immunohistochemical findings of pure DCIS and DCIS-looking invasive ductal carcinoma. Results (if a Case Study enter NA) Here, we reported a 55 year-old female who was noted to have microcalcification at the 11:00 o’clock of the right posterior breast on routine mammographic examination in 09/2023. Biopsy of the calcification area in 10/2023 reported high grade DCIS (ER+ PR-). Histologic examination of subsequent mastectomy specimen showed two separate DCIS-looking areas. Immunohistochemical (IHC) staining showed that myoepithelial markers, p63 and smooth muscle myosin heavy chain (SMMHC), were retained at the periphery of all the expanded acini in one area. Unexpectedly and surprisingly, p63 and SMMHC were completely lost at the periphery of part of the DCIS-looking acini in another area, immunohistochemically compatible with the diagnosis of invasive ductal carcinoma admixed with DCIS. Conclusion Knowing that invasive ductal carcinoma of the breast can present as DCIS-looking morphology, especially given the condition that the diagnosis of DCIS was rendered on the previous biopsy, will enhance awareness of pathologists to recognize sneaky DCIS-looking invasive ductal carcinoma in the extensive DCIS background. In turn, this will prevent misdiagnosis and under-treatment of patients with invasive ductal carcinoma of the breast.

Uncommon Presentation of Pulmonary Adenoid Cystic Carcinoma: A Case of Brain Metastasis in a Young Smoker

Abstract Introduction/Objective Pulmonary adenoid cystic carcinoma (PACC) is a rare entity, accounting for only 0.04-0.2% lung cancers, and mainly originating from the small salivary glands in the tracheobronchial tree. Due to slow-growing pattern and unspecific symptoms, the diagnosis is often delayed. While metastasis in PACC is uncommon, reports of brain metastasis are exceedingly rare. We present a case of PACC with metastasis to the brain in a young smoker. Methods/Case Report A 29-year-old female with history of smoking presented with headache, hypersomnia, episodes of vomiting and falling. Physical examination revealed multiple palpable nodes on the mid head, left temporal and right parietal area, left shoulder area were found. CT scan demonstrated complex cystic mass with a mural nodule within the left cerebellar hemisphere, with displacement of the cerebellar tonsils, as well as a 7.4 cm left infrahilar mass with heterogenous enhancement. Patient underwent craniotomy with tumor resection and left lower lobe endobronchial biopsy. Touch smear of the brain lesion showed clusters of hyperchromatic cells with myxoid like and hyalinized stroma. H&E stain showed cords of neoplastic cells embedded in a basophilic/myxoid stroma. Lung biopsy showed similar histological patterns. IHC stain showed the tumor cells were positive for epithelial and myoepithelial cells markers(CAM5.2, CK7, p63, Sox 10), retained INI1/BAF47 and BRG1 expression, negative for NUT and BCOR. Salivary Gland NGS Fusion Panel was performed and detected a MYBL1::NFIB [t(8;9)(8q13.1;9p23)] fusion alteration, which confirmed the diagnosis of adenoid cystic carcinoma. Considering no lesion was found in the patient’s head and neck, diagnosis of PACC was made. Results (if a Case Study enter NA) NA Conclusion PACC manifests three histologic subtypes: cribriform (most common), trabecular, and solid. In this case, brain and lung lesions exhibited similar patterns - nests of small, monomorphic cells within a myxoid-like and basophilic stroma background, consistent with trabecular pattern. Cytologically, densely packed cellular clusters were embedded in a myxoid like matrix. Distinguishing PACC from other salivary gland tumors is challenging. Immunostains for epithelial and myoepithelial cells, along with morphology, aid in diagnosis. The MYB::NFIB fusion helps differentiate from other lung salivary gland malignancies, but is found in a lower percentage of PACC cases (~40%) compared to other primary adnoid cystic carcinoma (~85%).

Striated duct adenoma: The cytological description of a rareentity.

Striated duct adenoma is a benign salivary gland tumour recently recognized by the World Health Organization. To date, no report has described the cytological features of this entity. We report the case of a 60-year-old woman with a tumour in the right parotid gland with a diameter greater than 2.4 cm confirmed by imaging tests. Two fine-needle aspiration cytologies (FNAC) were performed with inconclusive results, reporting epithelioid and spindle-shaped cellularity, with little stroma, and nuclei with abundant pseudoinclusions. Myoepithelioma and Schwannoma were proposed as differential diagnoses. An immunocytochemical panel was performed, showing positivity for S-100, SOX10, CK7 and vimentin, and negativity for both myoepithelial (p63 and calponin) and thyroid markers. In the absence of a conclusive diagnosis, the patient accepted surgery. The biopsy results confirmed diagnosis of striated duct adenoma, with immunohistochemical features superimposable to cytology. Little information is available in the literature, both on biopsy and, more strikingly, on cytology of this neoplasm. The aim of this work is to provide cytological characteristics that allow diagnosis of this entity with FNAC and thus avoid unnecessary surgeries.

Microcellular approach to submandibular gland senescence. Myoepithelial markers between aging and tumors

Microcellular approach to submandibular gland senescence. Myoepithelial markers between aging and tumors

Bronchial Basaloid Papillary Tumor of Uncertain Malignant Potential: A Case Report.

Bronchial papillomas are benign tumors, which can be divided into different subtypes based on the cellular features. So far, no bronchial papilloma with basaloid cell features has been reported. We report a bronchial basaloid papillary tumor in a 67-year-old woman. Tumor recurrence and malignant transformation were observed after a long-term follow-up. The clinical, histological, immunohistochemical, and genetic features were reappraised. The primary tumor was characterized by papillary growth pattern and basaloid neoplastic cells, only a small amount of neoplastic cells showed mature characteristics. The tumor originated from respiratory epithelium and had a low proliferation index by Ki-67. Keratin (KRT) 5/6 and KRT7 showed patchy or partial positivity. Myoepithelial markers were negative. P63 was diffusely positive, but it was negative in the small amount of tumor cells with mature characteristics. The common genetic alterations (EGFR, KRAS, BRAF V600E, HER2, and ALK) of lung cancers were not detected. However, tumor recurrence was observed in the mediastinum and esophagus 12 years after surgery. The recurrent tumor had a morphology overlapping with that of the primary tumor; however, it displayed significantly malignant characteristics. The recurrent tumor was not related to high-risk HPV. A high variant allele frequency was observed in tumor suppressor gene BRCA1, TP53, oncogene GNA11, and KIT, which were all missense mutations. Considering the bland features of the primary tumor and the fact of tumor recurrence and undisputed malignant transformation, the basaloid papillary tumor was considered a tumor with uncertain malignant potential.

Primary thymic adenoid cystic carcinoma with high-grade transformation: A clinicopathological and immunohistochemical analysis of 4 cases

Four cases of a distinct carcinoma of the thymic gland are presented. The patients were 4 adult males with an age range from 40 to 47 years (mean, 43.5 years). Clinically, all patients presented with non-specific respiratory symptoms. None of the patients had any prior history of head and neck neoplasm or surgery in that anatomic area. Large anterior mediastinal masses were found on diagnostic imaging with concurrent metastatic disease to pleura, lungs, regional lymph nodes and bones. Microscopically, all tumors were composed of a solid proliferation of hyperchromatic, monomorphic small cells with focal cytoplasmic clearing embedded in a fibromyxoid stroma. In one case, occasional duct-like structures were identified. Immunohistochemically, the tumors were positive for pancytokeratin, CD117 and MYB and negative for myoepithelial markers. Systemic chemotherapy was initiated in all patients. Despite therapy, clinical follow-up revealed that all 4 patients died of their disease 11–23 months after their initial diagnosis. The cases in this series highlight a tumor that is different from conventional thymic carcinoma and that has the morphological and immunohistochemical features commonly seen in adenoid cystic carcinomas with high-grade transformation. Correct diagnosis is essential for patient management.

Salivary Gland Tissue Recombination Can Modify Cell Fate

Although mesenchyme is essential for inducing the epithelium of ectodermal organs, its precise role in organ-specific epithelial fate determination remains poorly understood. To elucidate the roles of tissue interactions in cellular differentiation, we performed single-cell RNA sequencing and imaging analyses on recombined tissues, where mesenchyme and epithelium were switched ex vivo between two types of embryonic mouse salivary glands: the parotid gland (a serous gland) and the submandibular gland (a predominantly mucous gland). We found partial induction of molecules that define gland-specific acinar and myoepithelial cells in recombined salivary epithelium. The parotid epithelium recombined with submandibular mesenchyme began to express mucous acinar genes not intrinsic to the parotid gland. While myoepithelial cells do not normally line parotid acini, newly induced myoepithelial cells densely populated recombined parotid acini. However, mucous acinar and myoepithelial markers continued to be expressed in submandibular epithelial cells recombined with parotid mesenchyme. Consequently, some epithelial cells appeared to be plastic, such that their fate could still be modified in response to mesenchymal signaling, whereas other epithelial cells appeared to be already committed to a specific fate. We also discovered evidence for bidirectional induction: transcriptional changes were observed not only in the epithelium but also in the mesenchyme after heterotypic tissue recombination. For example, parotid epithelium induced the expression of muscle-related genes in submandibular fibroblasts that began to mimic parotid fibroblast gene expression. These studies provide the first comprehensive unbiased molecular characterization of tissue recombination approaches exploring the regulation of cell fate.

Peculiar nuclear atypia associated with MDM2 gene amplification in carcinoma ex-pleomorphic adenoma harbouring an alteration of HMGA2.

Salivary gland neoplasms (SGN) exhibiting the HMGA2::WIF1 fusion are recognized by their resemblance to histology found in canalicular adenoma. Recently, ~20% of cases among 28 HMGA2::WIF1-rearranged-SGN showed malignancy and adverse outcomes (recurrence, distant metastasis, and disease-specific mortality). Among them, MDM2/CDK4 amplifications were identified in one case. This outcome suggests that the MDM2/CDK4 amplifications could be useful to predict an aggressive course of carcinoma ex-pleomorphic adenoma (CEPA). We investigated the correlation between HMGA2 fusion and MDM2 amplification in four salivary gland neoplasms, providing detailed clinicopathological features and outcomes. Cases were selected from different institutions. Histological examination, immunohistochemistry, fluorescence insitu hybridization (FISH), RNA sequencing, and whole-exome capture were performed. The cohort included four CEPA cases, all female, aged between 32 and 89 years. Tumours arose from the parotid gland with an average size of 24.5 mm. None exhibited recurrence or distant metastases during the 4-5 months of follow-up. Pathologically, all cases displayed a peculiar atypical nuclei with 'gear-like appearance'. Immunohistochemically, tumours exhibited a biphasic pattern with myoepithelial and ductal differentiation markers. All cases showed HMGA2 overexpression and MDM2 amplification by FISH and RNA sequencing. In a control cohort of MDM2 nonamplified CEPA cases, not exhibiting the peculiar nuclear atypia. Our findings suggest a strong correlation between HMGA2 alteration/MDM2 amplification and a peculiar nuclear atypia, advocating for their evaluation in biphasic tumours to facilitate accurate diagnosis and tailored posttumour removal monitoring. Further studies are warranted to validate these observations and elucidate their prognostic implications.

Role of P63 in Benign and Malignant Lesions of Breast

Introduction: Breast carcinoma is leading cause of cancer death in women. Breast lesions constitute heterogeneous group of diseases with wide variety of etiologies ranging from inflammatory-benign- malignant lesions. There are several reported markers for immunohistochemical detection of myoepithelial cells. Smooth muscle specific proteins, such as smooth muscle actin, smooth muscle myosin heavy chain, calponin and h-caldesmon are used to highlight myoepithelium. p63 antibody is myoepithelial cell marker that selectively stains nuclei. It is negative in stromal, myofibroblastic and adipocytic cells.Aims and Objectives: The aim of this study was to establish role of p63 expression in distinguishing benign breast lesions, premalignant lesions and malignant tumors of breast.Materials and Methods: 30 cases were selected from core biopsy, lumpectomy and mastectomy specimens ofbreast received at department of Pathology, Chalmeda Anand Rao Institute of Medical Sciences during the period of January 2021 to December 2021 and were studied prospectively. All specimens were processed according to CAP protocol and reported . Immunohistochemistry was performed to determine p63 expression in those specimens. p63 expression was evaluated as continuous positive/discontinuous positive/negative.Ethical Approval: This study was reviewed and approved by institute ethics committee, CAIMS, Karimnagar.Results: Among total 30 cases, 18 cases (60%) were benign lesions and all were positive for p63 expression. 3 cases (9.99%) were premalignant and were least positive for p63 expression. All malignant cases 9 cases (29.99%) were negative for p63 expression.Conclusion: The Positive correlation was seen between histomorphological features and p63 scoring in all the lesions, So p63 is good Immunohistochemical marker for evaluating breast lesions.

Abstract 1076: Single nucleus RNA-sequencing using normal human salivary glands revealed a potential etiologic relationship between each salivary gland cell and salivary gland malignancies

Abstract Salivary glands are composed of several types of cells, and each cell type is predicted to be involved in the carcinogenesis of different types of cancers including Adenoid cystic carcinoma (ACC), Acinic cell carcinoma (AciCC), salivary duct carcinoma (SDC), myoepithelial carcinoma (MECA) and other histology. In this study, we performed single nucleus RNA-seq on three human salivary gland samples to clarify the gene expression profile of each complex cellular component of the salivary glands and related these expression patterns to expression found in salivary gland cancers (SGC) to infer cell of origin. By single nucleus RNA-seq, total 13,643 salivary gland cells were stratified into four clusters: acinar cells, ductal cells 1, ductal cells 2, and myoepithelial cells/stromal cells, with differentially expressed genes of each group. The localization of each cell group was anatomically validated by IHC of each cluster marker gene, and one group of ductal cells was found to represent intercalated ductal cells labeled with HES1. Gene ontology analysis for this group included “epithelial cell differentiation” confirming the intercalated duct. Furthermore, to elucidate the potential etiologic relationship between normal salivary glands cell type and salivary gland carcinoma histology, we compared the expression of each cluster marker to SGC public RNA-seq data. In comparison between AciCC and ACC, we used normalized RNA-seq data of 54 ACC and 21 AciCC. ACC had significantly less expression of acinar cells markers (STATH, CST2, and LPO) compared to other markers expression(***P = 4 × 10−51), unlike AciCC (P = 0.54), suggesting a possible contribution of acinar cells to the carcinogenesis of AciCC. In another cohort, we compared 16 SDC, and 38 MECA with publicly available RNA-seq data. Remarkably, HES1 and ELF3, each of two different ductal cell markers, were significantly upregulated in SDC consistent with origin of SDC from ductal cells (P=0.001, P=0.0007, respectively). Consistent with bulk RNA-seq results, expression of HES1 in IHC using clinical human SDC and MECA samples was higher in SDC than MECA, suggesting that the expression of the derived cells is involved in salivary gland carcinogenesis. Cell type expressions in specific SGC histology are similar to those found in normal salivary gland populations, indicating a potential etiologic relationship. On the other hand, there was no significant difference in myoepithelial marker ACTA2 expression between SDC and MECA, suggesting that the markers of origin are not always highly expressed, depending on cancer subtypes. Although publicly available SGC RNA-seq data used in this study are limited, the results remarkably reflect the diverse modes of carcinogenesis of SGC. These findings might provide a better understanding of the molecular basis of SGC and treatment strategies for SGC. Citation Format: Takuya Nakagawa, Chanond Nasamran, Jingjing Hu, Prakriti Sen, Theresa Guo, Kathleen Fisch, Joseph Califano. Single nucleus RNA-sequencing using normal human salivary glands revealed a potential etiologic relationship between each salivary gland cell and salivary gland malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1076.

Abstract A012: Molecular profiling of neoductgenesis in early stage breast cancer for the development of novel diagnostic biomarkers

Abstract Ductal carcinoma in situ (DCIS) is the most common precancerous finding in mammography screens. DCIS generally has a good prognosis, and only 20-25% of the cases progress to invasive breast carcinoma (IBC) even if left untreated. Breast pathologists and radiologists have suggested that there are currently more than one kind of DCIS under the same diagnosis. A subset of DCIS cases with reduced survival rate are associated with casting-type calcifications that can be histologically detected within closely packed, contorted, newly formed ducts, a phenomenon called neoductgenesis. Tumors with neoductgenesis are often erroneously diagnosed as DCIS, while in fact, they are associated with higher degree of metastasis and should be considered invasive carcinomas. This tumor category currently lacks specific histopathological markers and the biological processes leading to metastasis via neoductgenesis remain poorly characterised. To reveal new information of this breast tumor type, we are currently conducting comprehensive characterization of FFPE tissue samples of DCIS cases with and without neoductgenesis using imaging mass cytometry analysis and immunohistochemistry of specific tumor areas. Preliminary results on immunofluorescence staining suggest that neoductgenesis is associated with changes in the expression of specific myoepithelial marker proteins compared to areas with pure DCIS. In addition, we are analysing the three-dimensional ductal architecture of these lesions. The information obtained from this study can lead to development of new diagnostic tools for the identification of early breast cancers with a higher risk of spreading. Early detection of these cases is important to ensure the effectiveness and timeliness of treatment, and at the same time to improve the patients' quality of life. Citation Format: Laura Lehtinen, Leena Koskinen, Markus Peurla, Emilia Huotari, Otto Kauko, Peter Dean, Pauliina Hartiala, Pia Boström, Emilia Peuhu. Molecular profiling of neoductgenesis in early stage breast cancer for the development of novel diagnostic biomarkers [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A012.

CD10 expression as a potential predictor of pathological complete response in ER-negative and triple-negative breast cancer patients treated with anthracycline-based neoadjuvant chemotherapy

BackgroundNeoadjuvant chemotherapy (NCT) can induce a pathological complete response (pCR) in breast cancer patients, leading to improved outcomes. However, predicting which patients will achieve pCR remains a challenge. CD10, a myoepithelial marker, has shown diagnostic and prognostic value in metastatic tumors. Its potential as a predictor of chemosensitivity to anthracycline-based NCT in breast cancer is unknown. AimThis retrospective study aimed to investigate the potential of CD10 cancer cell expression as a predictive marker of chemosensitivity in breast cancers treated with anthracycline-based neoadjuvant chemotherapy. MethodsWe analyzed 130 patients with invasive ductal carcinoma who received anthracycline-based NCT. CD10 expression was assessed by immunohistochemistry on pre-treatment biopsies. Statistical analysis evaluated the association between CD10 expression and pCR rates. ResultsUnivariate analysis revealed that ER-positive and CD10-negative tumors had lower pCR rates [OR 7.4830 (95% CI 2.7762–20.1699); p = 0.0001]. Multivariate analysis confirmed ER status as a strong predictor of poor response [OR 0.085 (95% CI 0.024–0.30); p < 0.001] and CD10 expression as a predictor of a favourable response [OR 0.11 (0.8–0.19); p = 0.049]. CD10 expression significantly predicted pCR in ER-negative cases [OR 0.1098 (0.0268–0.4503); p = 0.0022] and triple-negative breast cancer [OR 0.0966 (95% CI 0.0270–0.3462); p = 0.0003]. Concordance was observed between core biopsies and excised samples. ConclusionPositive CD10 cancer cell expression may predict increased response to anthracycline-based neoadjuvant chemotherapy in ER-negative and triple-negative breast cancer cases. Further research is needed to validate these findings in larger cohorts and determine the clinical utility of CD10 as a predictive marker.

Sifter and Mesh-Cribriform Carcinoma Breast

Invasive cribriform carcinoma breast emerges as a low grade subtype of invasive carcinoma breast. Neoplasm preponderantly (&gt;90%) delineates a pure cribriform architecture or may represent as a mixed tumour composed of 10% to 90% of variant morphological subtype. Tumefaction is constituted of islands or nests of malignant epithelial cells demonstrating spherical or angulated contours or configure well defined cribriform spaces articulated by arches of epithelial cells, thereby delineating a sieve-like appearance with intercellular lumens impregnated with secretions. Miniature tumour cells display mild to moderate pleomorphism with absent nuclear atypia. Cribriform carcinoma breast is immune reactive to Oestrogen receptors(ER) or progesterone receptors (PR) and immune non-reactive to HER2 or diverse myoepithelial markers. Cribriform carcinoma breast requires segregation from neoplasms as adenoid cystic carcinoma, cribriform variant of ductal carcinoma in situ, collagenous spherulosis, well differentiated neuroendocrine tumour or well differentiated invasive breast cancer of no special type (NST). Neoplasm may be appropriately ascertained by mammography or ultrasonography of the breast. Cribriform carcinoma breast may be appropriately alleviated by primary surgical eradication of the lesion.

Epidermal and dermal cells from adult rat eccrine sweat gland-containing skin can reconstruct the three-dimensional structure of eccrine sweat glands

BackgroundPreviously, we have demonstrated that eccrine sweat gland cells (ESGCs) can reconstruct the three-dimensional (3D) structure of eccrine sweat glands (ESGs). However, there is still a need to explore source cells capable of regenerating ESG to address the issue of ESG regeneration in ESGC-deficient conditions, such as severe burns. MethodsThe epidermal cells and dermal cells in adult rat ventral foot skin (ESG-bearing) were isolated. The isolated single epidermal cells and dermal cells were mixed with Matrigel, and then the mixture was implanted into the axillary/inguinal fat pads of nude mice. Five weeks after implantation, the Matrigel plugs were harvested and the morphology and differentiation of the cells were examined by H&E staining and fluorescent immunohistochemical staining for ESG markers, such as Na+ -K+ -2Cl- cotransporter 1 (NKCC1), Na+ -K+ -ATPase (NKA), Foxa1 and K14. ResultsThe epidermal cells and dermal cells of adult rat ventral foot skin can reconstruct 3D structure and express specific markers of ESGs in skin, such as NKCC1, NKA and Foxa1, indicating the ESG-phenotypic differentiation of the 3D structures. Double immunofluorescence staining showed that some 3D structures expressed both the myoepithelial cell marker alpha-SMA and the common marker K14 of duct cells and myoepithelial cells, while some 3D structures expressed only K14, indicating that ESG-like 3D structures differentiated into duct-like and secretory coiled cells. ConclusionEpidermal and dermal cells from adult ESG-bearing skin can be used as a cell source for ESG regeneration.

Study of the Immunohistochemical Expression of p63 in Benign Lesions and Carcinoma of the Breast at a Tertiary Hospital in South India.

Invasive breast carcinoma is among the most common female cancers worldwide, causing high morbidity and mortality. Considerable disagreement in the interpretation of diagnostically challenging breast lesions based on histology alone has been documented. One of the essential histopathological findings that help distinguish benign from malignant lesions is the presence of the myoepithelial cell layer. Myoepithelial markers such as tumor protein 63 (p63) help distinguish invasive carcinoma from benign proliferations. p63 antibody is superior to other myoepithelial markers as it selectively stains the nuclei and is negative in stromal cells. To study the expression of p63 in various histological subtypes and grades of breast carcinomas. After routine hematoxylin and eosin stain, 65 cases of breast lesions were subjected to immunohistochemistry for p63 antigen using Novacastra ready-to-use monoclonal antibody p6. All cases were analyzed for p63 expression, and its staining arrangement was interpreted. In all benign lesions, immunoreactivity was noted in the myoepithelial cells, forming a continuous layer surrounding the luminal epithelial cells. The benign papillary lesions showed p63 staining in the fibrovascular core of the papillary fronds and at the periphery. A few single myoepithelial cells stained by p63 were also seen scattered discontinuously in ductal carcinoma in situ (DCIS). All invasive carcinomas and encapsulated papillary carcinomas were completely devoid of peripheral p63 staining of myoepithelial cells. p63 is a specific nuclear marker of myoepithelial cells in the breast and can, therefore, aid in distinguishing invasive ductal carcinoma from DCIS or rare questionable hyperplastic lesions. They also play a significant role in distinguishing various papillary lesions of the breast and, hence, can be incorporated into routine reporting for definitive diagnosis and accurate treatment.

Cell-type-specific tumour sensitivity identified with a bromodomain targeting PROTAC in adenoid cystic carcinoma.

Salivary gland adenoid cystic carcinoma (ACC) is a rare malignancy with limited treatment options. The development of novel therapies is hindered by a lack of preclinical models. We have generated ACC patient-derived xenograft (PDX) lines that retain the physical and genetic properties of the original tumours, including the presence of the common MYB::NFIB or MYBL1::NFIB translocations. We have developed the conditions for the generation of both 2D and 3D tumour organoid patient-derived ACC models that retain MYB expression and can be used for drug studies. Using these models, we show in vitro and in vivo sensitivity of ACC cells to the bromodomain degrader, dBET6. Molecular studies show a decrease in BRD4 and MYB protein levels and target gene expression with treatment. The most prominent effect of dBET6 on tumours in vivo was a change in the relative composition of ACC cell types expressing either myoepithelial or ductal markers. We show that dBET6 inhibits the progenitor function of ACC cells, particularly in the myoepithelial marker-expressing population, revealing a cell-type-specific sensitivity. These studies uncover a novel mechanistic effect of bromodomain inhibitors on tumours and highlight the need to impact both cell-type populations for more effective treatments in ACC patients. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Genetic and Immunohistochemical Profiling of Mammary Hidradenoma and Comparison to Mucoepidermoid Carcinoma

Mucoepidermoid carcinoma (MEC) is exceedingly rare in the breast, with <45 cases reported in the literature. Although estrogen receptor/progesterone receptor/human epidermal growth factor 2 triple-negative, MEC is characterized as a special subtype of breast carcinoma with significantly better prognosis than conventional basal-type tumors. Cutaneous hidradenoma (HA) is considered a benign adnexal neoplasm showing histomorphologic overlap with MEC. Rare cases of HA have also been reported in the breast, but these are relatively uncharacterized. In this study, we examined the clinicopathologic, immunohistochemical (IHC), and genetic features of 8 breast HAs, in comparison to 3 mammary MECs. All cases were positive for MAML2 break-apart fluorescence in situ hybridization. Eight cases demonstrated a CRTC1::MAML2 fusion, and one MEC harbored a CRTC3::MAML2 fusion; the latter is a novel finding in the breast. Mutational burden was very low, with only one HA exhibiting a MAP3K1 pathogenic alteration. By IHC, both MEC and HA demonstrated cell type–dependent expression of high- and low-molecular-weight keratins and p63, as well as negative to low-positive estrogen receptor and androgen receptor. Smooth muscle myosin and calponin highlighted an in situ component in the 3 cases of MEC; expression of these myoepithelial markers was negative in HAs. Additional distinguishing characteristics included the growth pattern and tumor architecture, the presence of glandular/luminal cells in HA, and overall higher IHC expression of SOX10, S100 protein, MUC4, and mammaglobin in MEC. Morphologic findings were also compared to a series of 27 cutaneous nonmammary HAs. Mucinous and glandular/luminal cells were identified in significantly more mammary HAs than nonmammary lesions. The findings provide insight into the pathogenesis of MAML2-rearranged neoplasms of the breast, underscore the overlapping genetic features of MEC and HA, and highlight similarities to their extramammary counterparts.

Automated Classification of Breast Cancer Across the Spectrum of ERBB2 Expression Focusing on Heterogeneous Tumors With Low Human Epidermal Growth Factor Receptor 2 Expression

PURPOSE Although pharmaceutical companies conduct clinical trials of novel human epidermal growth factor receptor 2 (HER2)-low–directed drugs, diagnosing HER2-low cancer by immunohistochemistry (IHC) and in situ hybridization (ISH) remains challenging. This study investigates the performance of first-in-kind computerized intelligence to classify samples across gene expression levels and differentiate HER2-low tumors. MATERIALS AND METHODS We classified 251 samples: 142 primary invasive breast cancers (IBCs), 75 ductal carcinomas in situ (DCIS), and 34 mammaplasties (reference) using mRNA expression data from the QuantiGene Plex 2.0 assay. We used g3mclass probabilistic software to assess the number of classes in the assay data, the mean and the variance in each class, diagnostic cutoffs, and the prevalence of each class in the study population. RESULTS HER2-low (IHC score of 1+ or 2+/ISH–) accounted for 31% of IBC. First, we discovered that HER2-low tumors were represented by cases with normal ERBB2 transcript levels that were expected to produce physiologic levels of HER2 (70%) and cases with abnormally upregulated unamplified ERBB2 (30%). We termed the latter cancers ERBB2-up as they do not meet the standard definitions for ERBB2 overexpression and amplification. Second, HER2-low IBC classified as ERBB2-up had not only abnormally increased luminal growth and adhesion markers ( ERBB2, ESR1, PGR, IGF1R, VAV2, VAV3, KRT8, CDH1) but also downregulated myoepithelial marker ( KRT5). The vascularization ( RAP1 and C3G), immune cell infiltration ( VAV1), and mesenchymal transition ( CDH2) markers were dysregulated. Finally, in the independent cohort of DCIS, 40% of HER2-low DCIS shared similar traits with HER2-low IBC except for rare downregulation of KRT5 and no change in C3G, VAV1, and CDH2. CONCLUSION We demonstrated how innovative bioinformatic tools could help diagnose cancer across the spectrum of ERBB2 expression to aid decision making for HER2-low.

Clinical and Histopathologic Analyses of Nasopharyngeal Hyalinizing Clear Cell Carcinoma: A Series of 26 Cases With Molecular Confirmation.

The aim of this study was to evaluate the clinicopathologic features, molecular characteristics, treatment strategy, and prognosis of nasopharyngeal hyalinizing clear cell carcinoma (HCCC). Retrospective observational case series. Institutional pathology records between 2006 and 2022 were searched for all cases of nasopharyngeal HCCC. We included 10 male and 16 female patients aged 30 to 82 years (median: 60.5y, mean: 54.6y). The most common symptoms were blood-stained rhinorrhea and nasal obstruction. Tumors most often involved the lateral wall of the nasopharynx, followed by the superior posterior wall. Microscopically, all tumor cells were arranged in sheets, nests, cords, and single cells in a hyaline/myxoid/fibrous stroma. The tumor cells were polygonal, with or without distinct cell borders, and displayed abundant clear-to-eosinophilic cytoplasm. All 26 cases were positive for pancytokeratin, CK7, p40, and p63 but negative for myoepithelial differentiation markers. Ki-67 labeling was low and ranged from 1% to 10%. All 26 cases demonstrated EWSR1 and EWSR1-ATF1 rearrangements, and no case demonstrated MAML2 rearrangement. Complete follow-up data were available for 23 patients: 14 patients underwent endoscopic surgery alone, 5 underwent radiation therapy followed by endoscopic surgery, 3 underwent radiation therapy followed by biopsy, and 1 underwent cisplatin chemotherapy before endoscopic surgery. Clinical follow-up ranged from 6 to 195 months; 13 patients (56.5%) were alive without tumor, 5 patients (21.7%) died of disease, 5 patients (21.7%) survived with tumor. HCCCs of the nasopharynx are rare tumors. The definitive diagnosis depends on histopathology, immunohistochemistry, and molecular studies. The optimal treatment for patients with nasopharyngeal HCCC is wide local excision. Radiation and chemotherapy might be good options for managing locally advanced cases. Nasopharyngeal HCCC is less indolent than previously thought. Tumor stage and the choice of treatment are key factors affecting the prognosis of nasopharyngeal HCCC patients.

Activated breast stromal fibroblasts exhibit myoepithelial and mammary stem cells features

BackgroundActive breast cancer-associated fibroblasts (CAFs) promote tumor growth and spread, and like tumor cells they are also heterogeneous with various molecular sub-types and different pro-tumorigenic capacities. MethodsWe have used immunoblotting as well as quantitative RT-PCR to assess the expression of various epithelial/mesenchymal as well as stemness markers in breast stromal fibroblasts. Immunofluorescence was utilized to assess the level of different myoepithelial and luminal markers at the cellular level. Flow cytometry allowed to determine the proportion of CD44- and ALDH1-positive breast fibroblasts, while sphere formation assay was used to test the ability of these cells to form mammospheres. ResultsWe have shown here that IL-6-dependent activation of breast and skin fibroblasts promotes mesenchymal-to-epithelial transition and stemness in a STAT3- and p16-dependent manner. Interestingly, most primary CAFs isolated from breast cancer patients exhibited such transition and expressed lower levels of the mesenchymal markers N-cadherin and vimentin as compared to their adjacent normal fibroblasts (TCFs) isolated from the same patients. We have also shown that some CAFs and IL-6-activated fibroblasts express high levels of the myoepithelial markers cytokeratin 14 and CD10. Interestingly, 12 CAFs isolated from breast tumors showed higher proportions of CD24low/CD44high and ALDHhigh cells, compared to their corresponding TCF cells. These CD44high cells have higher abilities to form mammospheres and to enhance cell proliferation of breast cancer cells in a paracrine manner relative to their corresponding CD44low cells. ConclusionTogether, the present findings show novel characteristics of active breast stromal fibroblasts, which exhibit additional myoepithelial/progenitor features.