Histological Subtype Of Breast Cancer Research Articles

Proteomic and transcriptomic profiling identifies mediators of anchorage-independent growth and roles of inhibitor of differentiation proteins in invasive lobular carcinoma

Invasive lobular carcinoma (ILC) is a histological subtype of breast cancer with distinct molecular and clinical features from the more common subtype invasive ductal carcinoma (IDC). ILC cells exhibit anchorage-independent growth in ultra-low attachment (ULA) suspension cultures, which is largely attributed to the loss of E-cadherin. In addition to anoikis resistance, herein we show that human ILC cell lines exhibit enhanced cell proliferation in ULA cultures as compared to IDC cells. Proteomic comparison of ILC and IDC cell lines identified induction of PI3K/Akt and p90-RSK pathways specifically in ULA culture in ILC cells. Further transcriptional profiling uncovered unique upregulation of the inhibitors of differentiation family transcription factors ID1 and ID3 in ILC ULA culture, the knockdown of which diminished the anchorage-independent growth of ILC cell lines through cell cycle arrest. We find that ID1 and ID3 expression is higher in human ILC tumors as compared to IDC, correlated with worse prognosis uniquely in patients with ILC and associated with upregulation of angiogenesis and matrisome-related genes. Altogether, our comprehensive study of anchorage independence in human ILC cell lines provides mechanistic insights and clinical implications for metastatic dissemination of ILC and implicates ID1 and ID3 as novel drivers and therapeutic targets for lobular breast cancer.

Patient treatment and outcome after breast cancer orbital and periorbital metastases: a comprehensive case series including analysis of lobular versus ductal tumor histology

BackgroundBreast cancer is the most common malignancy to spread to the orbit and periorbit, and the invasive lobular carcinoma (ILC) histologic subtype of breast cancer has been reported to form these ophthalmic metastases (OM) more frequently than invasive ductal carcinomas (IDC). We herein report our single academic institution experience with breast cancer OM with respect to anatomical presentation, histology (lobular vs. ductal), treatment, and survival.MethodsWe employed the natural language processing platform, TIES (Text Information Extraction System), to search 2.3 million de-identified patient pathology and radiology records at our institution in order to identify patients with OM secondary to breast cancer. We then compared the resultant cohort, the “OM cohort,” to two other representative metastatic breast cancer patient (MBC) databases from our institution. Histological analysis of selected patients was performed.ResultsOur TIES search and manual refinement ultimately identified 28 patients who were diagnosed with breast cancer between 1995 and 2016 that subsequently developed OM. Median age at diagnosis was 54 (range 28–77) years of age. ER, PR, and HER2 status from the 28 patients with OM did not differ from other patients with MBC from our institution. The relative proportion of patients with ILC was significantly higher in the OM cohort (32.1%) than in other MBC patients in our institution (11.3%, p = 0.007). Median time to first OM in the OM cohort was 46.7 months, and OM were the second most frequent first metastases after bony metastases. After diagnosis of the first distant metastasis of any kind, median survival of patients with ILC (21.4 months) was significantly shorter than that of patients with IDC (55.3 months, p = 0.03). Nine patients developed bilateral OM. We observed a significant co-occurrence of OM and central nervous system metastases (p = 0.0053). The histological analysis revealed an interesting case in which the primary tumor was of a mixed ILC/IDC subtype, while only ILC was present in the OM.ConclusionsOM from breast cancer are illustrative of the difference in metastatic behavior of ILC versus IDC and should be considered when treating patients with ILC, especially in those with complaints of visual acuity changes.

52P Characterising clinicopathological and biological parameters predictive of outcome for patients diagnosed with invasive lobular carcinoma

Invasive lobular carcinoma (ILC) is the second most commonly diagnosed histological subtype of breast cancer, comprising up to 15% of all cases. Considerable data suggest there are fundamental clinical and biological differences between ILC and the more commonly diagnosed invasive carcinoma no special type. We sought to characterise clinical, pathological and biological parameters that could predict prognosis in ILC that would aid in the understanding of tumour subtype and in the management of patients diagnosed with this subtype of disease.

135TiP GELATO-trial: Assessing the efficacy of carboplatin and atezolizumab in metastatic lobular breast cancer

Invasive lobular breast cancer (ILC) is a special histological breast cancer subtype and is characterized by the loss of E-cadherin and a distinct metastatic pattern. For this difficult to treat breast cancer, no effective treatment options are available after patients become resistant to endocrine treatment. Despite its specific histology and disease behavior, only a few clinical trials focus specifically on ILCs. Recently, emerging translational data suggest that a subgroup of ILC has remarkably high expression of immune-related (IR) genes and harbor relatively high amounts of tumor-infiltrating lymphocytes.

Abstract P6-08-04: Germline mutations in cancer predisposition genes in patients with invasive lobular carcinoma of the breast

Abstract Background: Invasive lobular carcinoma (ILC) of the breast accounts for approximately 10-15% of all histologic subtypes of breast cancer. However, apart from germline mutations in CDH1, the contributions of mutations in other cancer predisposition genes to ILC are largely unknown. Methods: The study population included 3,893 women with ILC of the breast who underwent germline multigene panel testing of cancer predisposition genes at Ambry Genetics from March 2012 to December 2016. The prevalence of predisposition gene mutations in women with ILC was assessed relative to 38,004 women with invasive ductal carcinoma (IDC) who underwent germline multigene panel testing at Ambry Genetics during the same timeframe. Associations between mutations in each gene and risk of ILC were evaluated using reference controls. Results: Of the 3,893 women with ILC included in this study, 70.7% were non-Hispanic white, 65.1% had a family history of breast cancer, and 96.4% had estrogen receptor (ER) positive breast cancer. The overall frequency of germline mutations in cancer predisposition genes (ATM, BARD1, BRCA1, BRCA2, BRIP1, CDH1, CDKN2A, CHEK2, MLH1, MRE11A, MSH2, MSH6, NBN, NF1, PALB2, PTEN, RAD51C, RAD51D and TP53) was 7.8% for women with ILC and 10.7% for women with IDC. Mutations in CDH1 were significantly more frequent (Odds Ratio (OR)=12.1, p<0.001), whereas mutations in BRCA1 (OR=0.1; p<0.001) and PALB2 (OR=0.4; p<0.001)were less frequent in women with ILC, compared to women with IDC. When restricting the analysis to ER positive cases only, significant differences in frequencies of ATM (OR=0.6, p=0.03), BRCA1 (OR=0.3, p<0.001), CDH1 (OR=7.7, p<0.001) and PALB2 (OR=0.3, p<0.001) were observed in ILC compared to IDC. By comparison with gnomAD reference controls, ATM, BRCA2, CDH1, CHEK2, PALB2 and PTEN mutations were significantly associated with an increased risk of lLC and IDC (OR>2), NBN mutations were associated with ILC (OR=3.4; p<0.001) but not IDC, and BRCA1 mutations were not associated with increased risk of ILC. Among 274 women with ILC over the age of 50 without history of any other cancer or a family history of breast or ovarian cancer, 14 (5.1%) were found to carry a mutation in one of the genes evaluated. Conclusions: In a large cohort of patients with ILC, the frequencies of germline mutations in cancer predisposition genes were similar between ILC and IDC except for ATM, BRCA1, CDH1 and PALB2. Six genes, in addition to CDH1, were found to be germline predisposition genes for ILC. A substantial proportion of patients older than 50 with ILC without a family history of breast or ovarian cancer or a personal history of other cancers were found to be mutation carriers. These findings improve our understanding of germline genetic drivers of ILC and suggest that multigene genetic testing should be considered for all ILC patients. Citation Format: Siddhartha Yadav, Holly LaDuca, Eric C. Polley, Chunling Hu, Steven N. Hart, Jie Na, Rohan Gnanaolivu, Brandon Smith, David E Goldgar, Tina Pesaran, Jill S. Dolinsky, Fergus J. Couch. Germline mutations in cancer predisposition genes in patients with invasive lobular carcinoma of the breast [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-08-04.

Abstract P3-08-66: Metaplastic breast cancer in patients older than 65 years

Abstract Background: Metaplastic breast cancer (MBC) is a rare histologic subtype of breast cancer. It comprises less than 1% of all breast cancers. We evaluated the clinical characteristics and outcomes of MBC in geriatric patients older than age 65. Methods: We reviewed the chart of the pathologically proven MBC cases from 2000-2017. Only patients with age more than 65 years were included in the study for analysis. Results: A total of 48 MBC patients were included in the study. Thirty-six (76%) were white and 11 (23%) black. The number of patients in stages I, II, III, and IV were 12, 26, 6, and 4, respectively; 39 (81%) had nuclear grade III. Three (6%) had progesterone receptor positive, 3 (6%) were Her2 positive, and 4 (10%) were estrogen receptor positive. The most common distant metastases were lung (20%), followed by bone (12%). Fifty percent had a lumpectomy, 11% had hormonal therapy, and 60% had radiation therapy. Only 50% of patients received chemotherapy, out of which 46% received anthracycline. On univariable analysis, stage of the MBC and metastasis to the lung, bone, and brain were associated with worse overall survival (OS). There was no statistical significance in OS when stage II was compared with stage I MBC. Stage III had median OS of 18 months with HR of 3.25 (95% CI 0.85, 12.44) (p=0.086) and stage IV had 10 months median OS with HR of 11.17, (95% CI 2.37, 52.62) (p=0.002). Hormonal therapy, radiation therapy, and type of chemotherapy (anthracycline vs. non-anthracycline) did not show any statistical significance in regards to OS and progression-free survival. Conclusion: In our study, MBC demonstrated overall poor survival and progression-free survival. Only stage of the MBC and metastasis to brain bone and lung proved to predict worse survival. Citation Format: Johnny Chahine, Bicky Thapa, Xuefei Jia, Abdo Haddad. Metaplastic breast cancer in patients older than 65 years [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-08-66.

Abstract P1-16-02: Survey of Lobular Breast Cancer Alliance website users confirms value and identifies unmet information needs

Abstract Introduction The Lobular Breast Cancer Alliance (LBCA) was founded in 2017 by patient advocates attending the First International Invasive Lobular Breast Cancer Symposium sponsored by the University of Pittsburgh. The conference underscored that invasive lobular breast cancer (ILC) is an understudied unique subtype of breast cancer requiring refinements in treatments. ILC is the sixth most frequently diagnosed cancer of women and the second most common histological subtype of breast cancer with more than 39,000 patients diagnosed a year in the U.S. LBCA’s goals are to advance research and educate about ILC. Challenges An early goal of LBCA was to address the absence of a central source of quality information about lobular breast cancer. A website, lobularbreastcancer.org, launched December, 2017 with over 98,000 hits to-date. It is maintained by patient-advocate volunteers with content reviewed by LBCA’s Scientific Advisory Board. Methods A survey of users was conducted from May 1 to June 3, 2019 to determine value of the website to users and identify potential ways to improve it. Specific goals were: Understand who was visiting the site, identify the information sought, obtain feedback on the usefulness of content, and seek input on content and navigation. Results The online survey was taken by 950 participants. Current or former patients treated for lobular breast cancer comprised 94.7% of respondents. 75.8% were from U.S. Health professionals/researchers represented 3.04% of responders. Patients ranged in age from under 35 to over 75 years; 71.5% were 46-65 years. Most (66.5%) had Stage 1-2 disease at time of diagnosis; 7% reported de novo metastatic disease. An additional 9% reported a metastatic recurrence. LBCA (43.8%), other cancer organizations (43.2%),and Internet searches (38.3%) were the most frequently used sources for information about lobular breast cancer; doctor/health care provider ranked fourth (35.3%). The survey confirmed that LBCA goals for the website were aligned with the reason responders visited - i.e., general information (33%), research/clinical trials (21.9%) and treatment information (17.8%). Most consulted the site 2-4 times (46%), 11% visited more than 10 times. Nearly all responders (83.7%) found the information they were seeking, and (45.4%) agreed that the LBCA website provided information they could not find elsewhere. There were 249 participants who responded to an open ended question with 273 recommendations for the site. The largest category of requests (17%) was for more frequent updates of research and treatment guidelines; requests for a list of providers with expertise in treating ILC patients and for LBCA to provide additional education about ILC to MDs/clinicians ranked second and third (11%). Conclusions LBCA is driving increased awareness of lobular breast cancer by sponsoring a website devoted to providing research-based information about lobular breast cancer. There were a number of actionable suggestions regarding organization and navigation of the LBCA website. Results confirmed that the LBCA goals for the website are aligned with the reason responders visited. Primarily, users searched for general information about ILC (33%), research/clinical trials (21.9%) and treatment information (17.8%). The need for a central online source for information about lobular breast cancer was confirmed by findings that the most frequently used sources of information about lobular were the LBCA, other cancer organizations and Internet searches. Doctors/health care providers ranked fourth as a source of information about lobular disease. Many responders wanted the website to list ILC treatment specialists, address the gap in provider expertise about ILC detection and treatment, and report research and treatment guidelines specifically for ILC. Citation Format: Lori Petitti, Janice Axelrod, Margaret Campbell-Kotler, Julia Levine, Flora Migyanka, Elizabeth Viggiano, Steffi Oesterreich, Leigh Pate. Survey of Lobular Breast Cancer Alliance website users confirms value and identifies unmet information needs [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-16-02.

Mucinous lesions of the breast: potpourri of old and new

Mucinous lesions of the breast encompass a range of benign and malignant entities characterized by extracellular mucin production. Increased sampling of mammary calcifications has identified a range of mucocele-like lesions, which are associated with benign proliferative and atypical intraductal epithelial proliferation ranging in architectural complexity from flat epithelial atypia to ductal carcinoma in situ. Mucinous carcinoma is a unique histologic subtype of breast cancer with a good prognosis. Mucinous carcinoma, especially in males and older females, can arise in association with solid papillary carcinoma. Recent molecular studies reveal distinct genomic changes in mucinous carcinoma. Micropapillary mucinous carcinoma is a recently described histologic variant of breast cancer with aggressive clinical features and poorer outcome. Not all mucinous lesions are of ductal epithelial phenotype; rarely, lobular carcinoma can present with extracellular mucin. This concise review discusses clinical features, histological findings, and differential diagnoses of mucinous lesions of the breast, including common and some rare lesions as well as recently described entities.

Prognosis of invasive micropapillary carcinoma compared with invasive ductal carcinoma in breast: A meta-analysis of PSM studies

BackgroundInvasive micropapillary carcinoma (IMPC) is a rare histological subtype of breast cancer. The outcome of IMPC remains controversial; we conducted a meta-analysis of propensity score matching (PSM) studies to evaluate the prognostic difference between IMPC and invasive ductal carcinoma (IDC). MethodsWe searched PubMed, EMBASE and the Cochrane library for PSM studies comparing survival data between IMPC and IDC. The summarized odds ratios (ORs) and 95% confidence interval (95% CI) are calculated by STATA software utilizing fixed-effect or random-effect models, depending on the heterogeneity of the eligible studies. ResultsEight PSM studies including 2102 IMPC patients are included in the meta-analysis. Compared with IDC, IMPC has a similar overall survival (OS) (estimated OR = 0.87, 95% CI: 0.61–1.25), but a shorter relapse free survival (RFS) (estimated OR = 1.31, 95% CI: 1.06–1.61); the shorter RFS might owe to the significantly higher loco-regional recurrence rate of IMPC (estimated OR = 3.60, 95% CI: 1.99–6.52). Funnel plots and Egger’s tests are used to evaluate publication bias and the p value for OS and RFS are 0.036 and 0.564 respectively. ConclusionsOur results demonstrate that compared with IDC, IMPC exhibits a similar, even favorite OS, but a shorter RFS; and the shorter RFS might owe to the significantly higher loco-regional recurrence rate of IMPC. These results could contribute to the individualized therapy and follow-up strategies for IMPC patients.

HIV and breast cancer - a mammographic analysis: An observational study to identify the mammographic pattern of breast cancer in HIV-positive patients.

Data on the association between HIV and breast cancer mammographic patterns and histological subtypes are limited. To determine whether specific mammographic findings, histological features and patient profiles were unique to a cohort of HIV-positive patients who developed breast cancer, by comparing them with a HIV-negative cohort. This was a descriptive study in which we conducted a retrospective chart review and mammographic and pathology analysis of newly diagnosed breast cancer patients referred to the Addington Hospital breast clinic between August 2008 and June 2012 and entered into a prospective database. Thirty-eight HIV-positive and 38 HIV-negative patients were included in the study. HIV-positive patients were more likely to have multifocal breast cancer (p=0.007), but not multicentric disease (p=0.05). The presence of grouped and fine pleomorphic microcalcifications and positive HIV status demonstrated statistical significance (p=0.000). A statistically significant relationship between grouped and fine pleomorphic microcalcifications with biopsies confirming high-grade ductal carcinoma in situ (HGDCIS) and HIV status was demonstrated (p=0.001). The mean age of the HIV-positive patients was 42.5 years (p=0.000). We demonstrated a statistically significant relationship between HIV status, the presence of multifocal breast cancer, and mammographically detected grouped and fine pleomorphic microcalcifications. A statistically significant relationship between HGDCIS and HIV status, and the presence of grouped and fine pleomorphic microcalcifications in HIV-positive patients with biopsies confirming HGDCIS, was demonstrated. Our study also showed that there is a relationship between age of presentation and HIV status.

Comparison of unsupervised machine-learning methods to identify metabolomic signatures in patients with localized breast cancer

Genomics and transcriptomics have led to the widely-used molecular classification of breast cancer (BC). However, heterogeneous biological behaviors persist within breast cancer subtypes. Metabolomics is a rapidly-expanding field of study dedicated to cellular metabolisms affected by the environment. The aim of this study was to compare metabolomic signatures of BC obtained by 5 different unsupervised machine learning (ML) methods. Fifty-two consecutive patients with BC with an indication for adjuvant chemotherapy between 2013 and 2016 were retrospectively included. We performed metabolomic profiling of tumor resection samples using liquid chromatography-mass spectrometry. Here, four hundred and forty-nine identified metabolites were selected for further analysis. Clusters obtained using 5 unsupervised ML methods (PCA k-means, sparse k-means, spectral clustering, SIMLR and k-sparse) were compared in terms of clinical and biological characteristics. With an optimal partitioning parameter k = 3, the five methods identified three prognosis groups of patients (favorable, intermediate, unfavorable) with different clinical and biological profiles. SIMLR and K-sparse methods were the most effective techniques in terms of clustering. In-silico survival analysis revealed a significant difference for 5-year predicted OS between the 3 clusters. Further pathway analysis using the 449 selected metabolites showed significant differences in amino acid and glucose metabolism between BC histologic subtypes. Our results provide proof-of-concept for the use of unsupervised ML metabolomics enabling stratification and personalized management of BC patients. The design of novel computational methods incorporating ML and bioinformatics techniques should make available tools particularly suited to improving the outcome of cancer treatment and reducing cancer-related mortalities.

Impact of histotypes on preferential organ-specific metastasis in triple-negative breast cancer.

BackgroundThe distant metastasis was the most predictive characters of poor prognosis for triple‐negative breast cancer (TNBC). We aimed to evaluate the correlation between patient characters and preferential distant metastatic sites (DMS) and its effects on prognosis.MethodsUsing the 2010‐2014 Surveillance, Epidemiology, and End Results Program (SEER) data, patients with TNBC were classified into eight histologic subtypes. Patient characters were compared using a chi‐squared test. Logistic regression was used for identification of predictive factors. The log‐rank testing was utilized with disease‐specific survival (DSS) and overall survival (OS) as the primary outcomes.ResultsA total of 23 270 patients with TNBC were involved, including 1544 patients with distant metastatic cancer. Bone metastasis was diagnosed in 559 cases, brain metastasis in 124 cases, liver metastasis found in 369 cases and lung metastasis in 492 cases. Histologic subtypes including metaplastic breast carcinoma and invasive lobular carcinoma showed significant differences in preferential DMS compared with invasive ductal carcinoma. Furthermore, we found different histologic subtypes with specific DMS showed various prognosis. We also evaluated different DMS of specific histologic subtypes showed different prognosis.ConclusionCertain histologic subtypes of breast cancer are associated with preferential DMS and prognosis; this knowledge may help to further understand the mechanism of breast cancer metastasis and to monitor the prognosis of patients with TNBC.

Pathway activity profiling of growth factor receptor network and stemness pathways differentiates metaplastic breast cancer histological subtypes

BackgroundGene expression profiling of rare cancers has proven challenging due to limited access to patient materials and requirement of intact, non-degraded RNA for next-generation sequencing. We customized a gene expression panel compatible with degraded RNA from formalin-fixed, paraffin-embedded (FFPE) patient cancer samples and investigated its utility in pathway activity profiling in patients with metaplastic breast cancer (MpBC).MethodsActivity of various biological pathways was profiled in samples from nineteen patients with MpBC and 8 patients with invasive ductal carcinoma with triple negative breast cancer (TNBC) phenotype using a custom gene expression-based assay of 345 genes.ResultsMpBC samples of mesenchymal (chondroid and/or osteoid) histology demonstrated increased SNAI1 and BCL2L11 pathway activity compared to samples with non-mesenchymal histology. Additionally, late cornified envelope and keratinization genes were downregulated in MpBC compared to TNBC, and epithelial-to-mesenchymal transition (EMT) and collagen genes were upregulated in MpBC. Patients with high activity of an invasiveness gene expression signature, as well as high expression of the mesenchymal marker and extracellular matrix glycoprotein gene SPARC, experienced worse outcomes than those with low invasiveness activity and low SPARC expression.ConclusionsThis study demonstrates the utility of gene expression profiling of metaplastic breast cancer FFPE samples with a custom counts-based assay. Gene expression patterns identified by this assay suggest that, although often histologically triple negative, patients with MpBC have distinct pathway activation compared to patients with invasive ductal TNBC. Incorporation of targeted therapies may lead to improved outcome for MpBC patients, especially in those patients expressing increased activity of invasiveness pathways.

Frequent amplifications of ESR1, ERBB2 and MDM4 in primary invasive lobular breast carcinoma.

Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer following invasive ductal carcinoma (IDC). To identify potential genetic drivers of ILC progression, we used NanoString nCounter technology to investigate the DNA copy number (CN) in 70 well-curated primary ILC samples. We confirmed prior observations of frequent amplification of CCND1 (33%), and MYC (17%) in ILC, but additionally identified a substantial subset of ILCs with ESR1 and ERBB2 (19%) amplifications. Of interest, tumors with ESR1 CN gains (14%) and amplification (10%) were more likely to recur compared to those with normal CN. Finally, we observed that MDM4 (MDMX) was amplified in 17% of ILC samples. MDM4 knockdown in TP53 wild-type ILC cell lines caused increased apoptosis, decreased proliferation associated with cell cycle arrest, and concomitant activation of TP53 target genes. Similar effects were seen in TP53 mutant cells, indicting a TP53-independent role for MDM4 in ILC. To conclude, amplification of ESR1 and MDM4 are potential genetic drivers of ILC. These amplifications may represent actionable, targetable tumor dependencies, and thus have potential clinical implications and warrant further study.

Heterogeneity in risk factors for ductal and lobular breast carcinomas: A case-control study.

Invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) of the breast are the most common histological subtypes of breast cancer. However, the associations and heterogeneity between histological subtypes and their risk factors are not well established. This study aimed to investigate risk factors for IDC and ILC. This case-control study included 1,009 incident breast cancer cases and 1,009 hospital controls, frequency-matched by age. Data were obtained from the patients' medical files and an interview administered via a questionnaire. Multinomial logistic regression was used and odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. The heterogeneity of the associations was assessed using the Wald test. Family history of breast cancer was associated with IDC (OR 2.64, 95% CI: 1.97-3.55) but not ILC (OR 0.81, 95% CI: 0.42-1.57; p for heterogeneity <0.001). Conversely, a history of miscarriage was associated with ILC (OR 1.71, 95% CI: 1.17-2.51) but not IDC (OR 1.18, 95% CI: 0.95-1.46; p for heterogeneity = 0.04). Similarly, type 2 diabetes was associated with ILC but not IDC (p for heterogeneity = 0.02). Age at first delivery and breastfeeding were significantly associated with IDC but not ILC, though p values for heterogeneity did not reach the significance level. Deliberate weight loss and age at menarche were significantly associated with ILC but not IDC (p for heterogeneity ≥0.27). Smoking, history of benign breast disease and BMI were associated with both subtypes. The present study supports the hypothesis that IDC and ILC are etiologically distinct tumours.

SNAIL is induced by tamoxifen and leads to growth inhibition in invasive lobular breast carcinoma.

Invasive lobular carcinoma (ILC) is a histological subtype of breast cancer that is predominantly estrogen receptor alpha (ER)-positive (+) and is thus treated with endocrine therapies. Herein, we sought to understand the molecular underpinnings of the 4-hydroxytamoxifen (4OHT) resistance in ILC by assessing the potential role of the epithelial-to-mesenchymal transition transcription factor (EMT-TF) SNAIL (SNAI1). Using a series of breast cancer cell lines, we measured the basal, estrogen and 4OHT-induced expression of SNAIL and other EMT-TF family members by quantitative reverse transcription-polymerase chain reaction and immunoblotting. Chromatin immunoprecipitation experiments were performed to assess ER binding to the SNAIL promoter. Cell proliferation, cell cycle and apoptosis were assessed in 2D cultures. 3D growth was assessed in Matrigel and Collagen I cultures. Estrogen and 4OHT induced SNAIL expression, but not that of the other EMT-TF family members SLUG (SNAI2) and SMUC (SNAI3), with the 4OHT effect being specific to the lobular but not the ductal subtype. We observed estrogen and 4OHT-induced ER recruitment to the SNAI1 promoter and high endogenous basal levels of SNAIL and several EMT-TFs in ILC cell lines. While SNAIL knockdown had a minor impact on the 4OHT partial agonism in estrogen-depleted conditions, it led to a surprising increase in cell proliferation in full serum. In complementary experiments, inducible SNAI1 overexpression caused decreased proliferation, associated with a cell cycle arrest in G0/G1. Additionally, apoptosis was observed in BCK4 cells. These data suggest a previously unrecognized role for SNAIL in ILC, substantiating a context-dependent behavior for this EMT-TF.

Abstract P3-07-04: Molecular characterization of mucinous breast cancers

Abstract Introduction Mucinous carcinoma, a special histological subtype of breast cancer (BC) which accounts for ˜2% of all invasive breast tumors, is characterized by the presence of extracellular mucin, typically expresses the estrogen receptor (ER), and lacks HER2 amplification. The majority of patients with mucinous BC are older at diagnosis, rarely present axillary lymph node metastases, and are associated with a better prognosis as compared to invasive ductal cancer patients (IDC, formally referred to as “breast cancer of no special type”). So far, it is unknown what is driving the mucinous phenotype of these tumors. Here we interrogated the genomics, transcriptomics, immune infiltration and epigenetics profiles of these tumors, using a retrospective institutional series and a publicly available dataset. Patients and methods After central pathology review and DNA extraction, a total of 31 pure mucinous cases from Institut J. Bordet Biobank were included (referred to as IJB cohort). Tumor infiltrating lymphocytes (TILs) were assessed on hematoxylin and eosin (H&amp;E). Low pass whole genome sequencing was conducted to assess ploidy and to detect copy number aberrations (CNAs). A second cohort was analyzed from a publicly available dataset (referred to as BRCA560 cohort), with available centrally reviewed histology subtyping and DNA methylation profiles (Nik-Zainal et al. Nature 2016). 207 ER+ primary BC, 14 of which were mucinous, had HumanMethylation450K methylation profiles. RNAseq was available for a subset of 145 cancers, 13 of which were mucinous. DNA methylation data was processed in R using the minfi package. Beta-values were normalized (preprocessQuantile) and dmpFinder was used to identify differentially methylated positions. Results In the IJB cohort, whole genome sequencing revealed that all but two tumors were diploid. The most frequently deleted cancer genes were RB1 (38,1%), CDH1 (23,8%), BRCA2 (38,1%),TP53 (23,8%), MAP2K4 (23,8%), EGFR (28,6%) and PGR (23,8%). In terms of amplifications, only ZNF217 (19,4%) and FGFR1/ZNF703 (9,5%) were observed. These mucinous tumors generally displayed low TIL levels (median=5%). In the BRCA560 cohort, there was no significant difference in the clinico-pathological features of ER+ IDC vs mucinous subtypes. At the genomic level, we identified a lower frequency of PIK3CA mutations as compared to ER+ IDC from the same cohort. At the DNA methylation level, we identified 8013 differentially methylated CpGs (q-val &amp;lt; .05) between IDC and mucinous tumors. The top differentially methylated CpG mapped to MUC2, an extracellular mucin. MUC2 was significantly demethylated in mucinous tumors as compared to IDC (q-val &amp;lt;.001). There was a negative association between methylation level of this CpG and MUC2 expression (rho = - 0.27, p&amp;lt; .001). Finally, MUC2 expression was significantly increased in mucinous tumors as compared to IDC (p&amp;lt; .001). Conclusion To the best of our knowledge, this study is the first to report hypomethylation of MUC2 in mucinous carcinoma of the breast, as a possible mechanism of extracellular production of mucin in these tumors. Furthermore, it highlights the minor immune infiltration of these cancers, possibly prevented by the mucin, and sheds light on the few genomic alterations present in these overall stable cancer genomes. Citation Format: Desmedt C, Veys I, Nguyen B, Leduc S, Bareche Y, Majjaj S, Boeckx B, Lambrechts D, Sotiriou C. Molecular characterization of mucinous breast cancers [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-07-04.

Abstract P3-06-03: Copy number analysis identifies ESR1 and MDM4 as drivers of progression in invasive lobular breast carcinoma

Abstract Background: Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer after invasive ductal carcinoma (IDC). While specific clinical and pathological features differ between ILC and IDC, both histologies are treated the same, due to a lack of knowledge of targetable pathways underlying the observed differences. To identify potential genetic drivers of ILC progression, we set out to identify genes with copy number (CN) alterations, comparing tumors with good outcome to those with poor outcome. Method: We designed probes for a total of 67 genes known to be frequently altered in breast cancer and used sensitive nanoString technology to comprehensively investigate CN alterations of these genes in 70 well-curated primary ILCs. ILC cell lines MDA-MB-134-VI, SUM44PE, and BCK4 were used for functional studies including proliferation, apoptosis, colony formation, and analysis of gene expression. Results: Our studies reveal that ESR1 is frequently amplified in primary ILC (14% gains and 10% amplification), and that tumors with amplified ESR1 are more likely to recur compared to those with normal CN. Our analysis also identified a subset of ILCs with HER2 amplification (19%) despite a negative clinical IHC score, and these tumors expressed high HER2 mRNA, protein, and demonstrated enrichment of a molecular HER2 signature. The other most frequently amplified genes included CCND1 (33%), MDM4 (17%), and MYC (17%), and most frequently lost genes were NCOR2 (7%), FGFR4 (6%) and TP53 (6%). MDM4, a negative regulator of p53, has previously been reported to play a role in breast cancer, though little is known about its role in ILC. We demonstrate that decreasing MDM4 levels in p53 wild type ILC cell lines results in increased apoptosis, decreased proliferation associated with cell cycle arrest, and activation of p53 target genes. Intriguingly, a similar induction of G0/G1 cell cycle arrest and increase in apoptosis was observed in p53 mutant ILC cells after MDM4 downregulation, suggesting a p53-independent function of MDM4. Conclusion: Sensitive detection of CN changes identified amplifications of ESR1 and MDM4 as potential drivers of ILC. Functional studies demonstrate that MDM4 has both p53 dependent and independent functions that warrant further study. Citation Format: Atkinson JM, Cao L, Basudan A, Sikora MJ, Bahreini A, Tasdemir N, Jankowitz RC, McAuliffe PF, Dabbs D, Haupt S, Haupt Y, Peter Lucas PC, Lee AV, Oesterreich S. Copy number analysis identifies ESR1 and MDM4 as drivers of progression in invasive lobular breast carcinoma [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-06-03.

Abstract P5-09-02: Clinical and pathological characteristics and screening outcome for secondary cancers of women with breast cancer and Li-Fraumeni syndrome

Abstract Background: Germline TP53 mutations predispose to early onset breast cancer in women and are associated with Li-Fraumeni syndrome. Published data on the clinical and pathological characteristics and screening outcome for secondary cancers among women with breast cancer and TP53 mutations is limited. To the best of our knowledge this is the largest cohort of breast cancer associated with Li-Fraumeni syndrome. Methods: Patients with breast cancer and Li-Fraumeni Syndrome were identified from a prospective research database from 2001 to 2017. Patients had genetic counselling and testing at The University of Texas MD Anderson Cancer Center and confirmed to have TP53 mutations associated with Li-Fraumeni syndrome. We reviewed the patient's charts to identify the clinical and pathological characteristics of their breast cancer. Data for secondary cancers are obtained only for patients with breast cancer as their initial cancer diagnosis and who are followed at The MD Anderson's Li-Fraumeni Education and Early Detection (LEAD) clinic which conducts comprehensive cancer screening for these patient's per the NCCN guidelines, including yearly whole body MRIs. Results: Fifty-nine patients confirmed to have Li-Fraumeni syndrome and breast cancer (100% female, median age 30 years). 94% of the patients were pre-menopausal at the time of breast cancer diagnosis and 6% were post-menopausal due to bilateral salpingo-oophorectomy. 61% were diagnosed after abnormal self or clinical breast exam and 26% based on abnormal screening mammography or ultrasound. In terms of the histologic subtype of breast cancer: 69% had invasive ductal carcinoma, 5% mucinous carcinoma, 5% mixed ductal and lobular, 5% sarcoma, 3% phylloides tumor and 13% with missing data. Pathologic stage per the 7th edition of AJCC cancer staging system was as follows: 23% stage I, 26% stage II, 23% stage III, 28% remaining with unknown pathologic stage. Pathologic markers include: 70% with positive estrogen receptor expression, 64% with positive progesterone receptor expression, 57% with HER-2 amplification defined per the ASCO-CAP HER-2 test guidelines and 7% with triple negative disease. Forty three patients were followed at LEAD clinic. Of the 43 patients, 40% (N=17) were diagnosed with 1 primary cancer other than breast cancer, 7% (N=7) with 2 primary cancers other than breast cancer and 44% (N=19) with breast cancer only. Out of the 43 patients, 5 were diagnosed with acute myelogenous leukemia, 4 with leiomyosarcoma, 3 osteosarcoma, 4 with other types of sarcoma, 4 with central nervous cell tumors (astrocytoma or glioblastoma multiforme), 3 with papillary thyroid carcinoma, 1 with pancreatic cancer, 1 with renal cell carcinoma, 1 adrenocortical carcinoma, 1 with uterine cancer, 1 with melanoma and 1 with cervical cancer. Conclusion: This study to our knowledge is the largest cohort of patient's with Li-Fraumeni syndrome and associated breast cancer that is followed in a dedicated clinic for patients with Li Fraumeni Syndrome. This cohort highlights the characteristics of patients with Li-Fraumeni syndrome and associated diagnosis of breast cancer as well as other primary cancers. Citation Format: Al-Awadhi A, Liu DD, Gutierrez-Barrera AM, Strong LC, Arun BK. Clinical and pathological characteristics and screening outcome for secondary cancers of women with breast cancer and Li-Fraumeni syndrome [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-09-02.

The Distribution and Outcomes of the 21-Gene Recurrence Score in T1-T2N0 Estrogen Receptor-Positive Breast Cancer With Different Histologic Subtypes.

Background: The clinical value of 21-gene recurrence score (RS) in various breast cancer histologic subtypes is not well established.Aims: To assess the distribution and outcomes of the 21-gene RS among various T1-T2N0 estrogen receptor-positive breast cancer histologic subtypes.Methods: Using the Surveillance, Epidemiology and End Results database, we investigated the distribution and outcomes of the 21-gene RS among various breast cancer histologic subtypes between 2004 and 2015. The histologic subtypes with 200 or more cases were further analyzed.Results: We identified 83,665 patients including eight histologic subtypes. The most common subtype was invasive ductal carcinoma not otherwise specified (IDC NOS) (77.9%), followed by lobular carcinoma NOS, mixed infiltrating duct and lobular carcinoma (IDC-L), mucinous adenocarcinoma, tubular adenocarcinoma, micropapillary ductal carcinoma, cribriform carcinoma NOS, and intraductal papillary adenocarcinoma with invasion with 10.8, 7.7, 2.1, 0.6, 0.3, 0.2, and 0.2%, respectively. The 5-years breast cancer specific survival (BCSS) was 98.8, 98.8, 98.9, 99.6, 100, 100, 100, and 100%, respectively (P = 0.011). Patients with IDC NOS (8.9%), micropapillary ductal carcinoma (8.8%), and intraductal papillary adenocarcinoma with invasion (8.2%) had significantly higher percentage of high-risk RS compared to other histologic subtypes (1.0–3.8%) (P < 0.001). The mean RS was higher in IDC NOS, lobular carcinoma NOS, and IDC-L compared to other subtypes. In multivariate analysis, 21-gene RS was the independent prognostic factor in patients with IDC NOS (P < 0.001), lobular carcinoma NOS (P < 0.001), and IDC-L (P < 0.001), patients with a higher RS was associated with poor BCSS.Conclusion: Our results demonstrate that there is a significant difference in distribution of 21-gene RS in T1-T2N0 estrogen receptor-positive breast cancer with different histologic subtypes. Long-term studies with larger series are needed to confirm the role of the 21-gene RS array in prognosis assessment and chemotherapy decision-making in special histologic subtypes with favorable prognosis.