Immunohistochemical Analysis of ER, PR, Her2 and CK5/6 in Infiltrative Breast Carcinomas in Indian Patients

Aim: Breast cancer is biologically a heterogeneous disease. Patients with the same diagnostic profile havemarkedly different clinical outcomes. Gene expression studies identified distinct breast cancer subtypes thatdiffer in prognosis. Aim is to identify the immunohistochemical subtypes of breast carcinoma and correlate theresults with pathological features associated with adverse prognosis in our study population.
Method: We included107 consecutive cases of invasive breast carcinoma and sub classified using immunohistochemical staining forER, PR, Her2, and CK5/6 into the following subtypes: luminal A, luminal B, basal-like, Her2+ and unclassified.Associations between tumor subtypes and tumor characteristics were examined.
Results: The proportion ofeach subtype in our patient population was: luminal A 37.4%, luminal B 11.1%, Her2+ 29% and basal-like7.5%. The following variables were significantly associated with IHC breast cancer subtypes: patient age (p<.05),overall histopathology grade (p<0.001), nuclear grade (p<0.005) and mitotic index (p<0.001). Her2+ and basallike subtypes were associated with poor differentiation (p<0.01), higher nuclear grade (p<0.05) and high mitoticindex (p<0.05).
Conclusions: Our data show a higher proportion of patients in the study population undergototal mastectomy and harbor poorly differentiated, node positive tumors than reported. There was also a relativelyhigh percentage of the Her2+ subtype (29%).