Radiotherapy for a recurrent Subclavicular ectopic breast carcinoma: Case report and detailed literature review

Ectopic breast carcinoma is an uncommon malignancy arising from accessory breast tissue located along the embryologic milk line. Subclavicular involvement is extremely rare and poses diagnostic and therapeutic challenges. We report the case of a 42-year-old woman presenting with a locally recurrent carcinoma arising from ectopic breast tissue located in the left subclavicular region, occurring six years after initial excision without adjuvant therapy. The patient underwent multidisciplinary management including radical surgery with modified radical mastectomy and wide excision of the ectopic lesion. Pathology confirmed invasive ductal carcinoma, Nottingham grade III, luminal B phenotype with lymphovascular invasion and close margins. Adjuvant treatment consisted of sequential anthracycline-taxane chemotherapy, endocrine therapy with tamoxifen, and hypofractionated intensity-modulated radiotherapy (IMRT) to the chest wall and ectopic tumor bed with boost. Dosimetric analysis confirmed adequate target coverage and satisfactory sparing of organs at risk. Acute toxicity was limited to grade 1 radiodermatitis. This case highlights the importance of recognizing ectopic breast carcinoma and supports a multidisciplinary treatment approach based on conventional breast cancer management principles when dedicated guidelines are lacking.