Molecular classification of breast cancer implications for pathologists Sarah E Pinder
Courtesy of CW Elston
Histological types
Breast Cancer Special Types 17 morphological special types 25-30% of all breast carcinomas Prognostic / clinical implications Different biological characteristics
Nottingham Primary Breast Cancer Study Histological type Excellent (>80% 10 year survival) Tubular, tubulo-lobular, invasive cribriform, mucinous Good (60-80% 10 year survival) Tubular mixed, alveolar lobular, mixed ductal NST & special type Moderate (50-60% 10 year survival) Medullary, atypical medullary, classical lobular, invasive papillary Poor (<50% 10 year survival) Ductal NST, solid lobular, lobular mixed, mixed ductal NST & lobular Pereira H et al. Histopathology 1995; 27; 219-226
Molecular Classification Hu et al. BMC Genomics 2006;7:96
What does this mean for pathologists? Should we be genotyping all invasive breast cancers? Is there a relationship between histological type and molecular type? Do special types have distinct molecular phenotypes?
Fresh tissue Expensive
Molecular classification not gene expression prognostic profiling Poor signature Good signature ER ve 37% 3% ER +ve 63% 97%
High throughput protein expression analysis using TMA DM Abd El-Rehim et al. Int J Cancer. 2005; 116; 340-50. TMAs of 1076 cases of invasive breast cancer Large panel of well-characterized commercially available biomarkers Related to epithelial cell lineage, differentiation, hormone & growth factor receptors & gene products
1200 1000 800 600 Linkage Distance 400 200 0 Abd El-Rehim et al. Int J Cancer. 2005; 116; 340-50
Membership of Clusters Luminal Ck & hormone receptor positive HER2 driven, hormone receptor weak/ negative, MUC1 positive, E-cadherin low p53-driven, hormone receptor negative, basal Ck positive HER2 positive, hormone receptor weak/ negative, MUC1 weak/negative, E-cadherin positive Broadly comparable to clusters in cdna studies; luminal & ER positive basal & ER negative HER-2 positive & ER negative/low
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N = 113 (11 special types of breast cancer) Operon arrays 24,650 genes TMAs 22 markers
Special types of breast cancer are homogeneous at the transcriptome level Luminal Basal-like Mol apocrine Mucinous A Classic ILC/ Tubular Mucinous B Neuroendocrine Micropapillary Adenoid cystic Medullary Metaplastic Pleomorphic ILC Apocrine Weigelt et al. J Pathol 2008
Luminal cancers Mucinous Tubular ILC Neuroendocrine
Infiltrating Lobular Carcinoma ER positive What does histological sub-type add?
E-cadherin inactivation & lobular carcinoma Encoded by the CDH1 gene (16q22.1) Adhesion molecule E-cadherin inactivation ALH LCIS Invasive LCs Mechanisms Mutation Deletion Methylation
E-cadherin inactivation & lobular carcinoma K14Cre;Trp53 F/F /Cdh1 F/F Introduced conditional E-cadherin mutations into mouse model based on epithelium-specific knockout of p53 Combined loss of E-cadherin & p53 resulted in accelerated development of invasive (and metastatic) mammary carcinomas, with strong resemblance to human ILC Derksen PW et al. Cancer Cell 2006;10;437-49
Increasing evidence that different histological types are genetically different FGFR1 as a potential therapeutic target for lobular breast carcinomas. Clin Cancer Res. 2006; 15;12:6652-62
What does intrinsic/molecular type add? This image cannot currently be displayed.
IHC Classification 205 tumours: 113 (55%) luminal A (strong ER+, HER2 -ve); 34 (17%) luminal B (weak to moderate ER, HER2 -ve); 32 (15%) triple negative (negative for ER/PR & HER2); 8 (4%) ERBB2 (negative for ER/PR but HER2+); 10 (5%) luminal A-HER2 hybrid (strong ER+ & HER2+) 8 (4%) luminal B-HER2 hybrid (weak to moderate ER+ & HER2+) Immunohistochemistry is a reliable surrogate tool to classify breast carcinoma according to the gene expression profile classification Bhargava R et al. Int J Clin Exp Pathol. 2009;2:444-55
Luminal breast cancers Sub-classification Luminal A Luminal B Grade 1 / 2 2 / 3 Proliferation Low High PR >95% ~75% Bcl2 High Low FOXA1 High Low HER2 Rare 5-50% TP53 mutations <10% ~35% Genomic changes Diploid Aneuploid Outcome (event in 5 yrs) 17% 43% Calza et al. Breast Cancer Res. 2006;8:R34
Luminal breast cancer Proliferation Ki67 is a prognostic marker for patients treated with endocrine therapy Dowsett et al. JNCI 2007; 99: 167-170
357 cancers Ki67 cut off; luminal B Vs luminal A = 13.25% JNCI 2009;1010;736-750 Independent cohort of 4046 cancers HER2 IHC & Ki67 (14%) to subtype into luminal A, luminal B, luminal-her2 +ve Luminal B & luminal-her+ve had poorer survival Women who received tamoxifen as sole adjuvant systemic therapy: - 10-year BCSS = 79% for luminal A, 64% for luminal B & 57% for luminal-her2 +ve patients
Challenges Standardised methodology/technical protocol Antibody QA for methodology Appropriate control material Education & QA for interpretation (heterogeneity, intensity, pattern, no. cells to count..) Defined, meaningful, validated cut-off Cut off - our panel has false-positive & false-negative rates of approximately 25%
Basal-like cancers
Molecular Classification Hu et al. BMC Genomics 2006;7:96
Metastatic pattern X X Tsuda et al. Am J Surg Pathol 2000; Hick et al. Am J Surg Pathol 2006; Fulford et al. Breast Cancer Res 2007
Histological features of Basal Cancers Grade 3 - low tubule formation, pleomorphic nuclei, many mitoses (grade scores = 333) Pushing growth front Central scar / acellular area Necrosis - often central or trabecular pattern, may be patchy Lymphocyte response Squamous or spindled cell / metaplastic areas
Basal-like phenotype ER PR HER2 EGFR CK17 Ck 5/6 Ck14 p-cad MIB1 p53
IHC & molecular classification Basal subtype defined as: Negative for ER, PR and HER2; Negative for ER and negative or positive for HER2; Positive for cytokeratin CK 5/6, CK14 and/or CK17; Positive for CK5/6, CK14, CK17 and/or EGFR and negative for ER, PR, and HER2 Compared 4 classifications in 195 breast carcinomas and found that rates of basal subtypes varied from 14% to 40% for invasive ductal carcinoma Ping Tang et al. Human Path 2009;38;506-513
Clin Cancer Res 2008; 14:1368-1376 TNT & basal Ck & EGFR -ve (5NP) TNT & basal CK +/- EGFR+ve (core basal)
Screen-detected Basal-like Cancer 356 women, screen-detected carcinomas > or = 10% cells with CK5/6 or CK14 defined as basal 43 (12%) basal phenotype; 313 non-basal 35% & 13% breast cancer deaths in basal group & nonbasal groups respectively In MVA -> grade, LN stage, LVI & basal immunophenotype prognostically significant 189 women, <15mm lesions 8 of 20 (40%) basal-like group Vs 5% non-basal died of breast cancer Evans AJ et al. J Med Screen 2007; 14; 210-214.
Adenoid Cystic Carcinoma t(6;9)(q22 23;p23 24) t(6;9)(q22 23;p23 24) translocation in ACC consistently results in a fusion of MYB oncogene to transcription factor gene NFIB All ACCs analyzed expressed the MYB-fusion indicating that MYB- NFIB fusion is hallmark of this type MYB-NFIB Persson M et al. PNAS 2009;106; 18740-4
Breast adenoid cystic carcinomas harbour the MYB-NFIB fusion gene 12 of 13 AdCCs - MYB-NFIB fusion gene Courtesy of J R-F
Special types of breast cancer are homogeneous at the transcriptome level Basal-like Adenoid cystic Medullary Metaplastic Weigelt et al. J Pathol 2008
Medullary-like carcinoma Histopathological and genetic characteristics Medullary-like carcinomas are found significantly more frequently in BRCA-1 carriers than in BRCA-2 carriers and control populations - Marcus et al, 1996; Breast Cancer Linkage Consortium, 1997; Lakhani et al, 1998; Lakhani et al, 1999
BRCA1 tumours - Basal-like Sorlie PNAS 2001 Familial BRCA1 tumours Sorlie PNAS 2003
Basal-like carcinomas BRCA1 downregulation BRCA1 methylation NST - Basal-like Medullary Metaplastic
SSB Inter-strand Crosslink repair Normal BRCA 1 function Reliant on BRCA1 for repair Replication fork collapse Deficient BRCA1 Error prone repair or No repair HR-based repair Survival Cell death due to chromosomal instability
Implication for treatment Often triple negative tumours Drugs exploiting a potential HR defect Platinum-based chemotherapy Triple Negative Trial (randomised phase II trial of docetaxel Vs carboplatin in advanced triple negative breast cancer) PARP inhibitors
HER2 cancers
Molecular classification of breast cancer implications for pathologists Need to sub-type invasive breast cancer accurately Histological type provides prognostic and biological information
Molecular classification of breast cancer implications for pathologists Need to work on universally agreed system for IHC panels (and scoring) for intrinsic types Ongoing challenge to assess molecular biomarkers accurately (& these will only increase in number) Diagnostic biomarkers (basal markers) Prognostic biomarkers (Ki67) Predictive biomarkers (new targets)