Invasive Carcinoma With Skin Adnexal Trichilemmal Hair Follicular Differentiation Occurring in the Breast: A Case Report With Detailed Immunohistochemical and Molecular Analysis

Cutaneous-type adnexal tumors involving the breast are rare and create a diagnostic dilemma as they are often indistinguishable from primary mammary neoplasms. Tumors showing hair follicular differentiation are particularly challenging due to their rarity and the subtle appreciation of the intricate microanatomy of the hair follicle. We report a triple negative cutaneous-type adnexal carcinoma with follicular differentiation involving the breast to bring attention to the existence of these specialized group of tumors which should be managed differently from conventional triple negative carcinomas of the breast.