A Novel Subset of Triple-Negative Breast Cancers with Unique Histology and Immunohistochemical Expression

Background & Objective: Triple-Negative Breast Carcinoma (TNBC) is characterized by an absence of estrogen receptor, progesterone receptor and HER۲ neu expression, with distinct molecular, histological and clinical features, aggressive clinical course and a poor prognosis. The objective was to evaluate the expression of Cytokeratin۵/۶ (CK ۵/۶), Epidermal Growth Factor Receptor ۱ (EGFR ۱), E-cadherin and Androgen receptor in tissue sections of TNBC.Methods: All modified radical mastectomy samples received negative for the three markers were subjected to further studies with CK۵/۶, EGFR ۱, E- cadherin and Androgen receptor staining. The clinical and pathological data were tabulated and statistically analysed using the Chi-square test, and cross-tabulation was done to assess the correlation between these markers.Results: Of ۹۴ samples classified as TNBC, ۳۱ (۳۳%) were positive for CK ۵/۶, ۴۷ (۵۰%) for EGFR, ۳۲ (۳۴%) for E Cadherin and Androgen receptor, respectively. We had one positive patient for all four markers, ۱۳ patients were negative for all four. Thirty-five cases were positive for only one marker, ۳۲ were positive for two markers, and ۱۳ were positive for three markers. Analysis revealed certain interesting patterns, namely - E cadherin was the most common isolated marker expressed in our cohort of TNBC with ۱۵ of ۳۵ positives.Conclusion: This study highlights the presence of a unique subtype of TNBC, which are negative for all the four markers studied here, with unique histomorphology of absent tumour necrosis and stromal lymphocytic infiltration being unique.

Keywords:

Androgen receptor , Breast cancer , CK ۵/۶ , EGFR , E- cadherin , Triple-negative