A Lobular Carcinoma in situ, Confined within a Fibroadenoma: A Case Report

Lobular carcinoma in situ (LCIS) is a rare, non-invasive lesion that serves as a marker for increased breast cancer risk. Its incidental identification within a fibroadenoma—a benign breast tumor—poses a diagnostic and management challenge due to the unusual coexistence of malignant and benign pathology. We present the case of a 31-year woman who presented with a painless, mobile lump in the right breast. Imaging suggested a well-defined, calcified lesion consistent with fibroadenoma. Histological examination following excision revealed a single focus of LCIS confined within the fibroadenoma, confirmed by loss of E-cadherin on immunohistochemistry. No invasive carcinoma was detected. This case highlights the importance of thorough histopathological assessment of fibroadenomas, particularly in young women, and the need for appropriate surgical excision and follow-up. Recognizing such rare associations is vital to avoid missed or delayed diagnoses and to inform clinical decisions regarding surveillance and risk stratification.