Clinicopathological Study of Triple Negative Breast Cancers

Triple Negative Breast Cancers (TNBC) are a subset of breast cancers which are composed of different molecular subtypes. The most common is the basal like subtype, which has an adverse prognosis and limited treatment options.

This study was undertaken to assess the clinico-pathologic and immunohistochemical subtypes of triple negative breast cancers and assess how each of these subtypes correlate with clinical behaviour and survival outcomes.

Fifty-three (22.2%) of 238 cases of primary invasive breast carcinomas diagnosed from January 2010 to June 2011 were found to be negative for immunohistochemical markers- ER, PR and HER2. These fifty three cases were included in the study and were classified into four histological subtypes proposed by Ishikawa et al. Basal markers- CK5/6, EGFR and CK14 were done on these cases and they were further classified immunohistochemically into basal and non basal subtypes. The morphological features, disease free survival and overall survival were evaluated for both basal and non basal subtypes.

Majority (96%) of TNBC cases were classified according to WHO as invasive ductal carcinoma (NOS). Type C Ishikawa histological subtype was found to be the commonest subtype in both basal and non-basal TNBC. Of 53 TNBC cases, basal immunohistochemical markers were performed on 47 cases only because of paucity of tissue. Of these 47 cases, thirty-five (74.4%) were found to be of basal like subtype and all these cases were picked up by a combination of CK5/6 and EGFR.

High grade morphological features, hormonal markers with additional use of basal markers can help identify the basal like subtype of TNBC, thereby predicting breast cancer survival. The combination of CK5/6 and EGFR identified all cases of basal subtype. EGFR in addition also has potential therapeutic implications. The morphological features and survival outcomes were not significantly different between basal and non-basal phenotypes.