Morphological, immunhistochemical features of basal like breast carcinomas and their correlation with prognostic factors

Breast carcinomas, which are the most frequent neoplasia in women, have been trying to be classified according to their gene expression profiles. Basal like carcinomas are the most prevalent group, due to their morphological and immunohistochemical characteristics, poor prognosis and unresponsive therapeutic features.Five hundred breast carcinomas, diagnosed at Pathology Department of Gazi University Medical School, were included in this study. Our aim was to determine the frequency of basal like breast carcinomas and to define their morphological features. The histopathological prognostic characteristics of the tumors and the value of morphological features in the definitive diagnosis were also evaluated. Histopathological prognostic factors (patient?s age, tumor size, lymph node metastasis, invasion of nipple, skin and fascia, histological tumor type and histological grade), structural morphological features (central scar and necrosis, geographic necrosis, stromal lymphocytic response, presence of carcinoma in-situ, growth pattern through the surrounding parenchyma, tubule formation, mitotic count) and cytological features (nuclear chromatin pattern, nuclear pleomorphism and amount of cytoplasm) were evaluated. Cytokeratin 14, cytokeratin 5/6, EGFR and vimentin were stained to all of the tumors and Her2/neu gene amplification was determined by FISH method.Tumors were classified as basal like breast carcinoma when they were triple negative and CK 5/6 and/or EGFR positive. According to this description, 9.4% of the carcinomas investigated in this study were ?basal like?. The invasive ductal carcinoma was the most frequent histological tumor type in this group and it was followed by medullary and metaplastic carcinomas. High mitotic index, high tubular and nuclear grade, the presence of central and/or geographic necrosis, pushing growth pattern, moderate to severe stromal lymphocytic response, vesicular nucleus with prominent eosinophilic nucleoli and the absence of carcinoma insitu were the most consistent morphological features with basal like carcinomas. When compared with the non-basal breast carcinomas, basal like carcinomas were found to be present in younger age groups and all their histological tumor grades were 3. Tumor size, lymph node metastasis and the presence of nipple, skin and/or fascia invasion did not show any difference between basal like and non basal breast carcinomas.The positivity of cytokeratin 14 and vimentin were shown to increase the diagnostic accuracy of basal like breast carcinoma.This study clearly showed that basal like breast carcinomas showed both morphological and immunohistochemical similarities to triple negative and CK5/6 and EGFR negative tumor group. However, ER(+) and PR(+) breast carcinomas, irrespective of their histological type, were the group that showed the major differences from basal like carcinomas in terms of the two parameters above.In conclusion, we observed a set of morphological features, not characteristic but helpful in the diagnosis, for basal like breast carcinomas in this study. We believe that the evaluation of the breast carcinomas which showed these features with an immunohistochemical panel including CK14 and vimentin could help in the definitive diagnosis of basal like carcinomas.