Residual Oncological Risk After Chest Masculinization Surgery: Invasive Breast Cancer 2 Years After Surgery.

Chest masculinization surgery (gender-affirming mastectomy [GAM]) is increasingly performed to achieve a masculine chest contour. Unlike oncological mastectomy, GAM prioritizes aesthetic outcomes and may leave residual glandular tissue. Although breast cancer after GAM is uncommon, its occurrence raises important clinical considerations regarding residual risk and surveillance. We report a case of invasive ductal carcinoma arising 2 years after subcutaneous chest masculinization surgery in a transgender patient without testosterone exposure or known hereditary cancer predisposition. Clinical, imaging, pathological findings, and management were reviewed. A 44-year-old transgender man presented with a palpable left chest wall mass 2 years after GAM performed at an outside private clinic, where no preoperative imaging or pathological evaluation had been performed. He had no known hereditary cancer predisposition. Imaging demonstrated a 1.2-cm lesion beneath the nipple-areolar complex. Core biopsy confirmed hormone receptor-positive, HER2-negative invasive ductal carcinoma. Germline testing was negative. The patient underwent completion mastectomy with an axillary evaluation, which revealed stage IIA disease with nodal involvement. Adjuvant chemotherapy, radiotherapy, and endocrine therapy were administered. At 9-month follow-up, the patient remains disease-free. This case highlights that chest masculinization surgery reduces but does not eliminate breast cancer risk. Residual glandular tissue may represent a potential substrate for malignancy, although causation cannot be definitively established. Preoperative imaging should be considered in patients meeting standard breast cancer screening criteria. Excised tissue may warrant histopathological evaluation. Surgeons should provide appropriate counseling and maintain appropriate postoperative cancer surveillance.