Site Of Breast Cancer Metastasis Research Articles

Site of breast cancer metastasis is independent of single nutrient levels.

Cancer metastasis is a major contributor to patient morbidity and mortality 1 , yet the factors that determine the organs where cancers can metastasize are incompletely understood. In this study, we quantify the absolute levels of over 100 nutrients available across multiple tissues in mice and investigate how this relates to the ability of breast cancer cells to grow in different organs. We engineered breast cancer cells with broad metastatic potential to be auxotrophic for specific nutrients and assessed their ability to colonize different organs. We then asked how tumor growth in different tissues relates to nutrient availability and tumor biosynthetic activity. We find that single nutrients alone do not define the sites where breast cancer cells can grow as metastases. Additionally, we identify purine synthesis as a requirement for tumor growth and metastasis across many tissues and find that this phenotype is independent of tissue nucleotide availability or tumor de novo nucleotide synthesis activity. These data suggest that a complex interplay of multiple nutrients within the microenvironment dictates potential sites of metastatic cancer growth, and highlights the interdependence between extrinsic environmental factors and intrinsic cellular properties in influencing where breast cancer cells can grow as metastases.

Organ-Specific Immune Setpoints Underlie Divergent Immune Profiles across Metastatic Sites in Breast Cancer.

Immune composition within the tumor microenvironment (TME) plays a central role in the propensity of cancer cells to metastasize and respond to therapy. Previous studies have suggested that the metastatic TME is immune-suppressed. However, limited accessibility to multiple metastatic sites within patients has made assessing the immune TME difficult in the context of multiorgan metastases. We utilized a rapid postmortem tissue collection protocol to assess the immune composition of numerous sites of breast cancer metastasis and paired tumor-free tissues. Metastases had comparable immune cell densities and compositions to paired tumor-free tissues of the same organ type. In contrast, immune cell densities in both metastatic and tumor-free tissues differed significantly between organ types, with lung immune infiltration being consistently greater than that in the liver. These immune profiling results were consistent between flow cytometry and multiplex immunofluorescence-based spatial analysis. Furthermore, we found that granulocytes were the predominant tumor-infiltrating immune cells in lung and liver metastases, and these granulocytes comprised most PD-L1-expressing cells in many tissue sites. We also identified distinct potential mechanisms of immunosuppression in lung and liver metastases, with the lung having increased expression of PD-L1+ antigen-presenting cells and the liver having higher numbers of activated regulatory T cells and HLA-DRlow monocytes. Together, these results demonstrate that the immune contexture of metastases is dictated by organ type and that immunotherapy strategies may benefit from unique tailoring to the tissue-specific features of the immune TME.

Breast cancer cells promote osteoclast differentiation in an MRTF-dependent paracrine manner.

Bone is a frequent site for breast cancer metastasis. Conditioning of the local tumor microenvironment (TME) through crosstalk between tumor cells and bone resident cells in the metastatic niche is a major driving force for bone colonization of breast cancer cells. The vast majority of breast cancer-associated metastasis is osteolytic in nature, and RANKL-induced differentiation of bone marrow-derived macrophages to osteoclasts (OCLs) is a key requirement for osteolytic metastatic growth of cancer cells. In this study, we demonstrate that breast cancer cell-secreted factors stimulate RANKL-induced OCL differentiation of BMDMs requiring the function of Myocardin-related transcription factor (MRTF) in tumor cells. This is partly attributed to the critical role of MRTF in maintaining the basal cellular expression of connective tissue growth factor (CTGF), a pro-osteoclastogenic matricellular factor known to promote bone metastasis in human breast cancer. Supporting these in vitro findings, bioinformatics analyses of multiple human breast cancer transcriptome datasets reveal a strong positive correlation between CTGF expression and MRTF gene signature further establishing the relevance of our findings in a human disease context. By Luminex analyses, we show that MRTF depletion in breast cancer cells has a broad impact on OCL-regulatory cell-secreted factors that extends beyond CTGF. These findings, taken together with demonstration of MRTF-dependence for bone colonization breast cancer cells in vivo, suggest that MRTF inhibition could be an effective strategy to diminish OCL formation and skeletal involvement in breast cancer. In summary, this study highlights a novel tumor-extrinsic function of MRTF relevant to breast cancer metastasis.

Abstract PO1-12-07: Denosumab vs. Pamidronate in the Management of Osteolytic Bone Metastases Secondary to Breast Cancer, a Multi-Institutional Analysis

Abstract Breast cancer is one of the most common cancers in women and is associated with poor outcomes due to the metastatic potential of high-grade tumors. One common site of breast cancer metastasis is to the bone, leading to serious adverse effects such as bone pain, bone fracture, and spinal cord compression. Denosumab, a monoclonal antibody against the receptor activator of nuclear factor kappa-b (RANK) ligand (RANKL), and Pamidronate, a bisphosphonate, are two pharmacologic agents offered for the treatment of these adverse complications. The goal of this study was to conduct a retrospective cohort analysis across multiple institutions to compare the efficacy of Denosumab vs. Pamidronate in the management of osteolytic bone metastases secondary to breast cancer by evaluating the risk of adverse events. TriNetX, an online network that provides access to anonymized medical records for more than 108 million patients in 72 large healthcare organizations, was used in this study. Two cohorts, consisting of 847 patients with a diagnosis of bone metastases and breast cancer, were created and subsequently matched for age, race, gender, and ethnicity. One cohort was given Denosumab while the other was given Pamidronate, and each cohort was excluded from receiving the other medication. The occurrence of pathologic fracture in each arm, spinal cord compression, and overall five-year survival rate was measured and analyzed. The results of this study showed that Denosumab had a statistically insignificant risk reduction in both pathological fracture (2.7% vs. 2.8%, p = 0.88) and spinal cord compression (2.6% vs. 2.7%, p = 0.88) and a statistically insignificant difference in the overall five-year survival rate (45.5% vs. 52.4%, p = 0.78) when compared to Pamidronate. As a result, additional factors such as financial cost, route of administration, dosing schedule, and potential adverse side effects should be discussed with each individual who requires pharmacological therapy for bone metastases secondary to breast cancer. Citation Format: Megan Bradley, Mabry Nichols, Brittany Miles. Denosumab vs. Pamidronate in the Management of Osteolytic Bone Metastases Secondary to Breast Cancer, a Multi-Institutional Analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-12-07.

CircLIFR-007 reduces liver metastasis via promoting hnRNPA1 nuclear export and YAP phosphorylation in breast cancer

Cancer metastasis is the major cause of death in patients with breast cancer (BC). The liver is a common site of breast cancer metastasis, and the 5-year survival rate of patients with breast cancer liver metastases (BCLMs) is only about 8.5 %. CircRNAs are involved in a variety of cancer-related pathological behaviors, and their unique structure and resistance to RNA degradation enable them to serve as ideal diagnostic biomarkers and therapeutic targets. Therefore, it is important to investigate the role and molecular mechanism of circRNAs in cancer metastasis. CircLIFR-007 was identified as a critical circular RNA in BC metastasis by circRNAs microarray and qRT-PCR experiment. Cell function assays were performed to explore the effect of circLIFR-007 in breast cancer cells. Experiments in vivo validated the function of circLIFR-007. Several molecular assays were performed to investigate the underlying mechanisms. We found that circLIFR-007 acted as a negative controller in breast cancer liver metastasis. CircLIFR-007 upregulates the phosphorylation level of YAP by exporting hnRNPA1 to promote the combination between hnRNPA1 and YAP in the cytoplasm. Overexpression of circLIFR-007 suppressed the expression of liver metastasis-related proteins, SREBF1 and SNAI1, which were regulated by transcription factor YAP. Functionally, circLIFR-007 inhibits the proliferation and metastasis of breast cancer cells both in vivo and in vitro.

Abstract 1496: The role of endothelial ACKR1 in breast cancer metastasis

Abstract Background: Tumor cells can co-opt mechanisms of leukocyte extravasation. Atypical Chemokine Receptor 1 (ACKR1) expression in endothelial cells has an established role in promoting leukocyte extravasation; however, the potential for endothelial ACKR1 to facilitate the metastatic process through the extravasation of tumor cells has not been studied. Methods: To understand ACKR1 function, we investigated endothelial ACKR1 expression at the distant metastatic site of the lung, a common site of breast cancer metastasis. We analyzed lung endothelial ACKR1 expression using immunofluorescent staining of lung vasculature during tumor progression in immunocompetent mice bearing orthotopically implanted E0771.LMB breast tumor cells. We assessed the timing of metastatic tumor cell arrival in the lung and evaluated the spatial relationship between disseminated tumor cells and ACKR1-positive vessels. To investigate secreted tumor factors that may mediate ACKR1 regulation in the lung, we performed intratracheal injections of TNF-alpha. We developed an endothelial cell specific ACKR1 conditional knockout mouse model (ACKR1 ECKO) to understand the impact of endothelial ACKR1 on primary tumor growth and subsequent lung metastasis in breast cancer. Results: Our results reveal a significant upregulation of ACKR1 in the lung endothelium of mice implanted with breast cancer cells in the mammary fat pad. Tumor-dependent ACKR1 expression was specifically localized to pulmonary venule endothelium, a common site of leukocyte and tumor cell extravasation. Lung endothelial ACKR1 expression became evident by day 13 after implantation, persisting through endpoint at day 28. Notably, ACKR1 upregulation occurred prior to tumor cell arrival in lungs of tumor bearing mice. We observed spatial clustering of disseminated tumor cells in proximity to ACKR1-positive vessels, implying a preferential site of tumor cell extravasation. In the absence of primary tumors, intratracheal delivery of TNF-alpha induced ACKR1 expression within lungs. When tumors were orthotopically implanted into our ACKR1 ECKO mouse model, we observed a marked decrease in lung metastases compared to control mice. Conclusion/Future Directions: We have determined that pulmonary ACKR1 expression is induced by breast tumors, and vessels expressing ACKR1 appear to act as entry points for lung metastasis. Loss of endothelial ACKR1 reduced metastasis, suggesting that endothelial ACKR1 regulates tumor cell extravasation at distant metastatic sites. We will upregulate lung endothelial ACKR1 expression and directly test its requirement for extravasation using an intravenous tumor cell injection metastasis model. Citation Format: Samuel Tanner Roach, Rishi Patel, Serena Thomas, Chinwe Ewenighi-Amankwah, Joseph Dufraine, L A. Naiche, Jan Kitajewski. The role of endothelial ACKR1 in breast cancer metastasis [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 1496.

A Representative Clinical Course of Progression, with Molecular Insights, of Hormone Receptor-Positive, HER2-Negative Bone Metastatic Breast Cancer.

Despite treatment advances, breast cancer remains a leading cause of death of women in the United States, mostly due to metastatic disease. Bone is a preferential site for breast cancer metastasis, and most metastatic breast cancer patients experience bone involvement at the time of death. The majority of patients with bone metastatic breast cancer are first diagnosed with and treated for early-stage disease, and from development of early-stage breast cancer to the recurrence of cancer in the bones, up to 30 years may elapse. Throughout this timeframe, a typical patient undergoes many treatments that have effects on the bone microenvironment. Therefore, this review explores the clinical course of a representative patient with hormone receptor-positive bone metastatic breast cancer, examining key treatment options at each stage and their effects on preventing and treating bone metastases.

Combining TIGIT Blockade with MDSC Inhibition Hinders Breast Cancer Bone Metastasis by Activating Antitumor Immunity.

Bone is the most common site of breast cancer metastasis. Bone metastasis is incurable and is associated with severe morbidity. Utilizing an immunocompetent mouse model of spontaneous breast cancer bone metastasis, we profiled the immune transcriptome of bone metastatic lesions and peripheral bone marrow at distinct metastatic stages, revealing dynamic changes during the metastatic process. We show that cross-talk between granulocytes and T cells is central to shaping an immunosuppressive microenvironment. Specifically, we identified the PD-1 and TIGIT signaling axes and the proinflammatory cytokine IL1β as central players in the interactions between granulocytes and T cells. Targeting these pathways in vivo resulted in attenuated bone metastasis and improved survival, by reactivating antitumor immunity. Analysis of patient samples revealed that TIGIT and IL1β are prominent in human bone metastasis. Our findings suggest that cotargeting immunosuppressive granulocytes and dysfunctional T cells may be a promising novel therapeutic strategy to inhibit bone metastasis. Significance: Temporal transcriptome profiling of the immune microenvironment in breast cancer bone metastasis revealed key communication pathways between dysfunctional T cells and myeloid derived suppressor cells. Cotargeting of TIGIT and IL1β inhibited bone metastasis and improved survival. Validation in patient data implicated these targets as a novel promising approach to treat human bone metastasis.

Tumor to Tumor Metastasis of Breast Cancer to Pheochromocytoma in a 77 Year Old Man

Abstract Introduction/Objective Male breast cancer is rare, accounting for less than 1% of all breast cancer diagnoses. The most common sites for breast cancer metastasis include bone, lung, liver and brain. Tumor-to-tumor metastasis is an unusual phenomenon where one distinct malignancy is present within the substance of another independent tumor. We present a case of a 77-year-old man with a left pheochromocytoma and a tumor to tumor metastasis (TTM) from breast cancer. To our knowledge, this is the first case of a TTM from a breast cancer to a pheochromocytoma in a man. Methods/Case Report The patient is a 77 year old man with a past medical history of a right pheochromocytoma resected 20 years ago and a recently diagnosed right breast cancer. PET-CT identified a left adrenal mass. Microscopic sections of the left adrenal gland showed nests of neoplastic cells arranged in a “zellballen” pattern. Adjacent to the neoplasm was a sheet of atypical epithelioid cells with increased nuclear to cytoplasmic ratios and frequent mitoses. Immunohistochemical stains were performed, and the nests of neoplastic cells with the zellballen pattern were positive for chromogranin and synaptophysin and negative for CAM5.2. A focus of the adrenal neoplasm was negative for these stains but stained positively for CAM5.2. Due to patient’s history, additional immunohistochemical stains were performed, staining with ER, CK7, GATA3, and mammaglobin was observed. These findings were interpreted as a tumor-to tumor metastasis of metastatic breast carcinoma to pheochromocytoma in the left adrenal gland. Results (if a Case Study enter NA) NA Conclusion Tumor-to-tumor metastasis (TTM) is an unusual phenomenon in which a primary tumor metastasizes into another tumor. Lung and breast carcinomas are the most common metastatic donors, while renal cell carcinoma and meningioma are the most common malignant and benign recipients. In patients with TTM, proper use of immunohistochemical stains and patient’s history can aid in the diagnosis of the distinct tumors.

Predicting Patterns of Distant Metastasis in Breast Cancer Patients following Local Regional Therapy Using Machine Learning.

Up to 30% of breast cancer (BC) patients will develop distant metastases (DM), for which there is no cure. Here, statistical and machine learning (ML) models were developed to estimate the risk of site-specific DM following local-regional therapy. This retrospective study cohort included 175 patients diagnosed with invasive BC who later developed DM. Clinicopathological information was collected for analysis. Outcome variables were the first site of metastasis (brain, bone or visceral) and the time interval (months) to developing DM. Multivariate statistical analysis and ML-based multivariable gradient boosting machines identified factors associated with these outcomes. Machine learning models predicted the site of DM, demonstrating an area under the curve of 0.74, 0.75, and 0.73 for brain, bone and visceral sites, respectively. Overall, most patients (57%) developed bone metastases, with increased odds associated with estrogen receptor (ER) positivity. Human epidermal growth factor receptor-2 (HER2) positivity and non-anthracycline chemotherapy regimens were associated with a decreased risk of bone DM, while brain metastasis was associated with ER-negativity. Furthermore, non-anthracycline chemotherapy alone was a significant predictor of visceral metastasis. Here, clinicopathologic and treatment variables used in ML prediction models predict the first site of metastasis in BC. Further validation may guide focused patient-specific surveillance practices.

Metastasis of breast cancer to bones alters the tumor immune microenvironment

BackgroundBone is one of the most frequent sites for breast cancer metastasis. Breast cancer bone metastasis (BCBM) leads to skeletal morbidities including pain, fractures, and spinal compression, all of which severely impact quality of life. Immunotherapy is a promising therapy for patients with advanced cancer, but whether it may provide benefit to metastatic bone cancer is currently unknown. Thus, a better understanding of the immune landscape of bone-disseminated breast cancers may reveal new therapeutic strategies. In this study, we use histopathological analysis to investigate changes within the immune microenvironment of primary breast cancer and paired BCBM.MethodsSixty-three patients with BCBM, including 31 with paired primary and bone metastatic lesions, were included in our study. The percentage of stroma and stromal tumor-infiltrating lymphocytes (TILs) was evaluated by histopathological analysis. The quantification of stromal TILs (CD4 + and CD8 +), macrophages (CD68 + and HLA-DR +), programmed cell death protein 1 (PD-1), and programmed cell death protein ligand 1 (PD-L1) was evaluated through immunohistochemical (IHC) staining. Statistical analysis was performed with paired t test, Wilcoxon test, spearman correlation test, and univariate and multivariate cox regression.ResultsMedian survival after BCBM pathological diagnosis was 20.5 months (range: 3–95 months). Of the immune parameters measured, none correlated with survival after bone metastasis was diagnosed. Compared to the primary site, bone metastases exhibited more tumor stroma (mean: 58.5% vs 28.87%, p < 0.001) and less TILs (mean: 8.45% vs 14.03%, p = 0.042), as determined by H&E analysis. The quantification of primary vs metastatic tissue area with CD4 + (23.95/mm2vs 51.69/mm2, p = 0.027 and with CD8 + (18.15/mm2vs 58.95/mm2, p = 0.004) TILs similarly followed this trend and was reduced in number for bone metastases. The number of CD68 + and HLA-DR + macrophages showed no significant difference between primary sites and bone metastases. PD-1 expression was present in 68.25% of the bone metastasis, while PD-L1 expression was only present in 7.94% of the bone metastasis.ConclusionsOur findings suggest that compared to the primary breast cancer site, bone metastases harbor a less active immune microenvironment. Despite this relatively dampened immune landscape, expression of PD-1 and PD-L1 in the bone metastasis indicates a potential benefit from immune checkpoint inhibitors for some BCBM cases.

Abstract P6-05-50: Lobular Breast Cancer Alliance Inc. Survey of Individuals with Metastatic Invasive Lobular Carcinoma

Abstract Background: The Lobular Breast Cancer Alliance Inc. (LBCA) is committed to raising awareness of the distinctive characteristics of invasive lobular carcinoma (ILC) and promoting and funding ILC research. Comprising 15% of all breast cancers, ILC tumors often form in a linear, sometimes diffuse fashion both within the breast and in metastatic sites, making them difficult to diagnose, monitor, and treat. LBCA surveyed individuals living with metastatic ILC (mILC) about their experiences with detection and monitoring of mILC. Methods: LBCA conducted an anonymous, online survey of persons living with mILC using SurveyMonkey. The survey was shared with LBCA newsletter subscribers, sister organizations, and via social media. Survey questions asked about metastatic site locations, imaging and monitoring modalities, and patient experience with disease progression and clinician discussions about mILC. An independent IRB review determined the study was exempt from full IRB review. Results: 241 people living with mILC completed the survey. 77% were from the US and Canada. 71% were between 35-64 years of age. 41% had been diagnosed with de novo metastatic ILC. Bone was the most common site of initial metastasis with 75% diagnosed de novo (DN) and 59% diagnosed with a distant recurrence (DR). GI metastases (including metastases to stomach, colon, bowel, peritoneum, or rectum) were reported by 11% of the DN and 14% of the DR groups, respectively. Unusual sites for breast cancer metastasis (to genitourinary organs, eye, or skin) were reported by 11% of the DN and 16% of the DR groups. Metastatic progression was reported by 47% of respondents including to bone (42%), to the liver (22%), and 40% reported progression within the initial metastatic site. 36% of individuals with DN mILC reported progression as compared to 54% among those with a DR. Both groups reported living with mILC for similar durations (on average 3.9 years for DN; 3.3 for DR). 36% of respondents reported that at least one imaging modality failed to visualize one or more of their metastatic sites at initial diagnosis of mILC. 54% of respondents with bone metastases and 19% of those with GI metastases indicated their metastases had not been visualized by standard imaging modalities. 48% of all surveyed stated their mILC was an unexpected or an incidental finding made during another medical procedure, of those, 64% were bone metastases. 25% of respondents whose metastases progressed indicated imaging failed to detect one or more of their sites of progression. In both the DN and DR groups, the most frequently utilized tests and/or procedures used to monitor for progression or changes in metastases were routine blood and tumor marker tests. Respondents with DN mILC reported an average 12 months between first report of symptoms and mILC diagnosis. Those with DR reported an average 8 months between symptom reporting and diagnosis. 42% of all respondents reported that a doctor had told them what symptoms to report at any time. 58% of respondents reported feeling that non-oncologists caring for them (primarily PCPs, radiologists, and gastroenterologists) needed to be better informed about ILC. Conclusion: Surveyed individuals confirmed the perception that mILC can occur in unique locations and be difficult to diagnose and that mILC may be challenging to monitor, and standard surveillance methods may fail to visualize mILC. While a large percent of respondents reported that their mILC diagnoses were unexpected or incidental findings during another medical procedure, this may be due to different understandings of “incidental.” This and the fact that more respondents with DR mILC reported progression than those with DN mILC warrant further study. Citation Format: Laurie B. Hutcheson, Janice Axelrod, Ann Camden, Donna J. Charlevoix, Tracy A. Cushing, Maxine S. Jochelson, Megan L. Kruse, Theresa Langdon, Julia K. Levine, Christine McKay, Otto Metzger, Mason Mitchell-Daniels, Jason Mouabbi, Barbara F. Neilsen. Lobular Breast Cancer Alliance Inc. Survey of Individuals with Metastatic Invasive Lobular Carcinoma [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 P6-05-50.

GREM1 in HER2+ breast cancer: worse prognosis, larger tumours and more bone metastasis

Breast cancer is the leading cause of female cancer deaths. Bone is the commonest site of breast cancer metastasis (40%) will be in the bone. Bone Morphogenetic Protein (BMP) antagonists have been shown to stimulate glycolysis as well as epithelial mesenchymal transition (EMT), which increases the motility of malignant cells and contributes to the development of metastases. The role of GREM1 in HER2+ breast cancer progression remains an under-researched yet promising area of study.

Metastatic Invasive Lobular Carcinoma of Bilateral Breasts Presenting with an Abdominal Mass

Background: Breast cancer remains the most frequent malignancy in women, with the two most common histological subtypes of breast cancer being the invasive ductal carcinomas (IDC) and invasive lobular carcinomas (ILC). The most common sites of breast cancer metastases are the liver, lung, pleura, brain and bone. Gastrointestinal, peritoneal, gynaecological and renal metastases are less common, often masquerading as primary malignancies and causing diagnostic confusion, mostly occurring in ILC as compared to IDC. Case Presentation: We report a case of a young woman presenting with an enlarging abdominal mass which was suspicious of a primary abdominal malignancy. Endoscopy and gastric biopsy revealed poorly differentiated carcinoma. On the top-most slices of her abdominal CT, bilateral enhancing breast lesions were detected, suspicious of metastases. Ultrasound and biopsy done for the breast lesions showed bilateral ILCs. Further staining of the gastric biopsy specimen confirmed the final diagnosis of gastric metastases from bilateral breast ILCs rather than a primary gastric tumour with breast metastases. Conclusion: This case highlights how breast cancer metastases to the GI tract may mimic primary GI cancers as well as the importance of breast examination, family history, radiological and pathological examination in detecting the breast origin of advanced carcinomas. Awareness of the different patterns of metastatic spread of ILC and IDC is also important due to the infiltrating nature and non-specific imaging findings of these tumours, requiring a high index of suspicion from the surgeons, oncologists, radiologists and pathologists.

Metastatic Lobular Carcinoma of the Breast Masquerading as Gallstone Disease – A Case Report

The gallbladder is a rare site of breast cancer metastasis. We report the patient case of a 60-year-old woman with isolated metastasis to the gallbladder, which was surgically removed for symptomatic cholelithiasis, with a subsequent new diagnosis of infiltrating lobular carcinoma (ILC) of the breast. ILC tends to metastasize to unusual sites such as the gastrointestinal and genitourinary tracts, but these usually occur concurrently with other more common sites of distant metastasis such as the bone, lungs, and liver. Our case underscores the need for routine histologic examination of gallbladder after cholecystectomy.

S3032 Hiding in Plain Sight: An Atypical Presentation of Metastatic Breast Cancer as Acute Decompensated Cirrhosis

Introduction: Liver is a common site of breast cancer metastases, which are typically identified as hypervascular lesions on imaging. We present a rare case of breast cancer leading to diffuse, intra-sinusoidal, radiographically occult metastases in a patient presenting with new hepatic decompensation. Case Description/Methods: A 65-year-old woman with a remote history of grade IIIa invasive ductal carcinoma of the right breast status post lumpectomy, chemotherapy, and local radiation therapy was referred to liver clinic for 1 month of abdominal pain and newly elevated AST 144 U/L, ALT 143 U/L, total bilirubin 5.2 mg/dL, conjugated bilirubin 3.7 mg/dL, and alkaline phosphatase 652 U/L. She denied use of alcohol, substances, new medications, or supplements. Physical exam did not demonstrate stigmata of chronic liver disease. Work up for infectious, autoimmune, and common infiltrative etiologies of liver disease were negative; several tumor markers were elevated (Table 1). A routine surveillance PET-CT and subsequent MRCP demonstrated diffuse heterogeneous liver attenuation with cirrhotic morphology, splenomegaly, trace ascites, and intrabdominal lymphadenopathy. No discrete masses were seen on either study. The following week the patient was admitted for rapidly progressive failure to thrive, worsening ascites, jaundice, and oliguria. Inpatient labs demonstrated worsening hyperbilirubinemia (total bilirubin 14.8 mg/dL, conjugated bilirubin 12.2 mg/dL), hyponatremia, and AKI. Admission MELD-Na score was 31 and CLIF-C ACLF score was 46. Paracentesis demonstrated SAAG 1.6 with ascites protein 1.8 g/dL confirming Child Pugh Class B Cirrhosis. Transjugular liver biopsy measured hepatic venous pressure gradient 12mmHg and pathology demonstrated metastatic breast carcinoma of the sinusoidal and vascular spaces with background steatosis and non-bridging fibrosis. Despite aggressive treatment with fulvestrant and abemaciclib, she had worsening multiorgan failure. Given her overall poor prognosis, the patient elected to transition to hospice. Discussion: Metastatic breast cancer uncommonly presents with diffuse, intra-sinusoidal metastases that are radiographically occult. This case highlights the importance of maintaining a high index of suspicion for metastatic disease in patients with a history of malignancy presenting with new hepatic decompensation even in absence of typical radiographic findings. In such cases, liver biopsy may be required for a definitive diagnosis. (Table) Table 1. - Work up for etiologies of chronic liver disease Autoimmune markers ANA Positive (1:320, speckled) Anti-mitochondrial Ab < 1:20 dsDNA < =200 Smooth muscle Ab < 20 RNP Ab < 20 SSA Ab 68 (Elevated) SSB Ab < 20 Rheumatoid Factor < 10 Thyroid Peroxidase Ab 135 (Elevated) Beta-2-Glycoprotein IgA/IgG/IgM < 10 Cardiolipin IgA/IgG/IgM < 20 C-ANCAMyeloperoxidase AbP-ANCAProteinase-3 Ab < 1:20< 1:20< 1:20< 1:20 Infectious studies Hep A Ab Nonreactive Hep C Ab Nonreactive Hep B surface Ab < 10 Hep B surface Ag Nonreactive Hep B core Ab Nonreactive MTB-Quantiferon-Gold Negative Other causes of Liver Disease Alpha-1-antitrypsin Negative SPEP/UPEP No monoclonal bands observed Ceruloplasmin Elevated Copper Elevated Ferritin Elevated Tumor Markers AFP 4.2 ng/mL, decreased to < 1.82 ng/mL CEA 84 ng/mL, increased to peak 3042 ng/mL (Elevated) CA 125 930 U/mL CA 19-9 1166 U/mL CA 27.29 7450.1 U/mL (Elevated)

Rectal linitis plastica as the first presentation of metastatic lobular breast cancer: an endoscopic ultrasound diagnosis

Gastrointestinal tract is an uncommon site of breast cancer metastasis. Rectal linitis plastica (RLP) is a rare presentation of rectal neoplasia, both primary and secondary, and refers to a diffuse infiltration of the wall by an infiltrating carcinoma. Diagnostic assessment of RLP may be challenging since cross-sectional imaging and endoscopic findings may be nonspecific, and endoscopic biopsies are frequently non-diagnostic due to the submucosal disease localization. Endoscopic ultrasound (EUS) with fine needle biopsy (FNB) is widely used for the diagnostic assessment of sub-epithelial lesions of upper and lower gastrointestinal tract. However, data about the use of EUS in case of rectal linitis plastica are very poor. We present a case of rectal metastasis as the first presentation of lobular breast cancer, presenting as rectal linitis plastica and diagnosed with EUS-FNB.

Clinical Characteristics, Prognostic Factors and Treatment Outcomes of Patients with Bone-Only Metastatic Breast Cancer.

IntroductionBone is the most frequent site of breast cancer metastasis. Differences between those who present with de novo bone-only metastasis (BOM) and those who progress to bone-only disease following a diagnosis of early-stage breast cancer are not clear. Such differences in clinical course might have an impact on the aggressiveness of treatment. This study presents the clinical and pathological features, along with treatment outcomes, of breast cancer patients with BOM in relation to the timing and type of bone metastasis.Patients and MethodsPatients with breast cancer and BOM were retrospectively reviewed. De novo BOM was defined as bone metastasis diagnosed at presentation or within the first 4 months of follow-up. Treatment outcomes of patients with de novo, compared to those with subsequent BOM, are presented.Results242 patients, median age (range) at diagnosis was 52 (27–80) years were enrolled. The majority of the patients (77.3%) had de novo BOM with multiple sites of bone involvement (82.6%). At a median follow-up of 37.7 months, the median overall survival (OS) for patients with de novo BOM disease was significantly shorter than those who developed so subsequently; 40.8 months (95% CI, 51.1–184.1) compared to 80.9 months (95% CI, 36.4–47.9), p < 0.001. Tumor grade, hormone receptor status and type of bone lesions (lytic versus sclerotic) had a significant impact on survival outcomes.ConclusionBreast cancer with de novo BOM is a distinct clinical entity with unfavorable prognosis and is associated with shorter survival. Several risk factors for poor outcomes were identified and might inform treatment plans.

Abstract 5985: Marrow immune landscape participates dormancy and activation of disseminated tumor cells in a breast cancer bone metastasis model

Abstract Breast cancer has the highest incidence rate among women and the second-highest mortality rate in cancer-related death in the world. Although the research on breast cancer treatment has made some progress, metastatic breast cancer is still incurable. Bone is the most common site for breast cancer metastasis. This work is dedicated to the use of mass cytometry and single cell analysis to explore the molecular alterations in the marrow immune microenvironment which participates the dormancy and activation of disseminated tumor cells (DTCs). Firstly, four Balb/c mouse breast cancer bone metastasis groups were established. Animals were divided into intracardiac injection group (n=10), subcutaneous injection group (n=10), tumor resection and suture group (n=10), and control group (n=10). In the intracardiac injection group, a breast cancer bone metastatic model was constructed by directly injecting mCherry-labeled 4T1 cells into the left ventricle. After detecting obvious bone metastasis by bioluminescence imaging (BLI), femur and tibia bone marrow were excised for flow cytometry cell sorting, mass cytometry and single cell analysis. Both the subcutaneous and the resection and suture groups were injected with mCherry-labeled 4T1 cells into the right-back of Balb/c mice. In the tumor resection and suture group, the tumor was removed at the time when the subcutaneous tumor was just palpable. In the subcutaneous injection group, the animals were sacrificed when tumor volume reached 1 cubic centimeter. The classification of bone marrow cells was determined by using fluorescent dye labeled CD45, CD4, CD8, CD19, NK1.1, CD11b, CD11c, IA/IE, Ly6C, Ly6G and other antibodies. Constructed as a local immune landscape in the marrow, certain numbers of B cells and T cells, in the bone marrow of mice with breast cancer bone metastasis were significantly less than those in control mice, indicating that the acquired immunity of the mice with bone metastasis is diminished. In addition, the proportions of CD11b+ myeloid cells and neutrophils in the marrow of mice with bone metastasis were significantly higher than that in the control group, whereas the proportion of macrophages and eosinophils were all significantly decreased indicating that the bone marrow immune environment has changed in the process of tumor occurrence and metastasis. Research is ongoing, including ex-marrow spleen cell analysis in those animals, to explore the mechanism of the interaction between the immune microenvironment and tumor cells that determines tumor heterogeneity and sensitivity to therapy. This work was supported by NSFC projects 81773146, 81972766, 81972420; Shenzhen Science and Technology Commission Project JCYJ20180302174235893; and College students' innovative entrepreneurial training program (S202114325028) Citation Format: Yingxuan Gong, Yinghao Wang, Xinyu Jiang, Xiuzhi Li, Yueming Li, Ming Chang, Yi Lu, Jian Zhang. Marrow immune landscape participates dormancy and activation of disseminated tumor cells in a breast cancer bone metastasis model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5985.

Eosinophils Decrease Pulmonary Metastatic Mammary Tumor Growth.

Metastatic breast cancer is challenging to effectively treat, highlighting the need for an improved understanding of host factors that influence metastatic tumor cell colonization and growth in distant tissues. The lungs are a common site of breast cancer metastasis and are host to a population of tissue-resident eosinophils. Eosinophils are granulocytic innate immune cells known for their prominent roles in allergy and Th2 immunity. Though their presence in solid tumors and metastases have been reported for decades, the influence of eosinophils on metastatic tumor growth in the lungs is unclear. We used transgenic mouse models characterized by elevated pulmonary eosinophils (IL5Tg mice) and eosinophil-deficiency (ΔdblGATA mice), as well as antibody-mediated depletion of eosinophils, to study the role of eosinophils in EO771 mammary tumor growth in the lungs. We found that IL5Tg mice exhibit reduced pulmonary metastatic colonization and decreased metastatic tumor burden compared to wild-type (WT) mice or eosinophil-deficient mice. Eosinophils co-cultured with tumor cells ex vivo produced peroxidase activity and induced tumor cell death, indicating that eosinophils are capable of releasing eosinophil peroxidase (EPX) and killing EO771 tumor cells. We found that lung eosinophils expressed phenotypic markers of activation during EO771 tumor growth in the lungs, and that metastatic growth was accelerated in eosinophil-deficient mice and in WT mice after immunological depletion of eosinophils. Our results highlight an important role for eosinophils in restricting mammary tumor cell growth in the lungs and support further work to determine whether strategies to trigger local eosinophil degranulation may decrease pulmonary metastatic growth.