Immunohistochemical Expression of p16 in Breast Carcinoma and its Correlation with Clinicopathological Parameters

Abstract

Background: Breast carcinoma is the most prevalent malignancy among women globally. The tumour suppressor protein p16 (INK4a) plays a pivotal role in cell cycle. Aberrant p16 expression has been linked to distinct molecular subtypes of breast carcinoma. This study aimed to evaluate the immunohistochemical (IHC) expression of p16 in invasive ductal carcinoma (IDC) of the breast. Materials and Methods: A total of 50 cases of IDC, NOS, obtained from modified radical mastectomy specimens, were included from June 2020 to December 2025. Results: The mean age of presentation was in the fifth decade (46–65 years, 52%). p16 showed positive expression (moderate + strong) in 48% (n=24) of cases. p16 positivity was observed in TNBC (76.9%), and the lowest in HER2-enriched tumours (10.0%), with a near-significant trend (P=0.0526). Conclusion: p16 IHC expression demonstrates subtype-specific patterns in breast carcinoma, with predominant positivity in triple-negative tumours and consistent negativity in HER2-enriched tumours.