[268] Analysis of Histopathologic Features Predictive for the Diagnosis of "Basal" like Breast Carcinoma

Mukund N Sable, Tanuja M Shet, Asawari J Patil, Bharti G Ramnani, Sangeeta B Desai. Tata Memorial Hospital, Mumbai, Maharashtra, India

Background: Breast cancer is classified into five subgroups based on gene expression profiling. Of the five subgroups, Basal like breast cancer (BLBC) is a poor prognostic subgroup having limited treatment options. Majorities of triple negative (ER/PR/CerbB2) breast cancers (TNBC) are BLBC, but both entities are not synonymous. The aims and objectives of this study were to assign breast tumours to “basal” category using histopathologic criteria documented in published literature, to study expression of various “basal” markers described in published literature in these tumours using IHC, and to compare the diagnosis based on surrogate “basal” markers on IHC with that offered on histopathologic features.
Design: Two hundred and five-naïve TNBCs (2005-2008) were studied for histopathological features viz. grade, architectural pattern, stromal responses, cytomorphology, duct carcinoma in situ (DCIS) and metaplastic differentiation. They were classified as BLBC-M (morphology) and non- BLBC. Simultaneously, they were evaluated for basal cytokeratins (CK5/6, CK 14 and CK 17) and EGFR to classify them as BLBC-I (immunohistochemistry) or core basal phenotype by using criteria of any basal cytokeratin and/or EGFR positivity. Remaining TNBCs were considered as nBLBC (7 markers negative). Using logistic regression (SPSS16 software) both BLBC-M and BLBC-I were analyzed for each histological feature. Multiple logistic regression was employed to identify the features which could predict the BLBC.
Results: Among 205 TNBC, 91% cases were BLBC (core). Histological features viz. mixed type of margin (p= 0.046), moderate inflammatory response (p= 0.031), absence of intraduct component (p= 0.034) and prominence of nucleoli (p= 0.042) were frequently associated with BLBC than nBLBCs. All other morphological features were insignificant to distinguish between BLBC (core) and nBLBC. On multiple logistic regression, absence of DCIS (p= 0.041), was the only one feature which could predict BLBC (core) in TNBC study group.
Conclusions: Morphology and immunohistochemistry do not assist in correct identification of BLBC (Core basal) phenotype from non-BLBC in TNBC study group. In the present study, absence of DCIS was the only histopathologic feature, which could predict BLBC independently. Well-characterized and standardized IHC signature would help accurate identification of BLBC and impart uniformity among various studies.
Category: Breast

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 1, Tuesday Morning


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