Comparison of Clinicopathological Parameters and Molecular Classification of Breast Cancers

AIM OF THE STUDY: This is a retrospective study of 60 cases, to detect the expression of ER, PR, HER2neu, CK5/6 and Ki67 proliferation index in breast carcinomas by immunohistochemical method and to determine the newer molecular classification. Few patients have recurrence inspite of being diagnosed under the category of low risk and few do well in the high risk group which can be attributed to the molecular level differentiation. The aim of this study to classify the patients under molecular classification, to compare the clinicopathological parameters with it and to denote the significance of targeted therapy. MATERIALS AND METHODS: This is a retrospective study of detecting the expression of the above said markers in modified radical mastectomy specimens received at the Institute of Pathology, Madras Medical College and Rajiv Gandhi Government General Hospital, Chennai during the period from January 2011 to June 2013. 4 microns thick sections of the paraffin tissue blocks were Hematoxylin and eosin stained and reported as Infiltrating ductal carcinoma no special type (IDC NST) and its special variants like medullary, papillary, metaplastic, lobular, mucinous and apocrine carcinoma. A total of 60 cases which included 30 of IDC NST and 30 cases of special variants were selected for immunohistochemical analysis. RESULTS: Out of the 60 cases studied, the most common was found to be the luminal A type comprising 37% and the least common was the luminal B and hybrid types each comprising 8%. The most common grade for HER2 was Grade III (50%). The association of histological grade with the molecular classification was statistically significant with the p value of 0.01. Basal type (56%) had the highest incidence of N3 stage.ER, PR, HER2 neu, CK5/6 expression and proliferation index with Ki67 had a statistically significant association with the molecular classification. High proliferation index (>14%) with Ki67 was noted in Luminal B, Basal and Hybrid types. 78% of the total 60 cases were alive and healthy. One death was reported in HER2, Hybrid and Basal types. The negative kappa value obtained while studying the agreement between the histopathological and molecular classification, indicates that the agreement is worse than chance and hence the importance of molecular classification is substantiated for the targeted therapy. CONCLUSION: To conclude, breast cancers are heterogenous and having diverse clinical outcomes, these researches on molecular subgroups would pave way towards the “personalisation” of treatment for breast cancers with the more feasible and economic tool of immunohistochemistry