RESUMEN
Ectopic breast tissue (EBT) is breast tissue located outside the normal anatomic boundaries of the breasts, developing due to incomplete embryological regression of the mammary ridges. EBT can develop anywhere along the milk line, with the axilla being the most common site. While generally benign, EBT can undergo malignant transformation. This case report discusses a 24-year-old female with locally advanced invasive ductal carcinoma in the axillary EBT, highlighting its clinical presentation, diagnostic process, and management in a resource-limited setting. The patient underwent wide local excision and axillary lymph node dissection followed by adjuvant chemotherapy and radiotherapy, achieving a favorable short-term outcome. This case underscores the importance of considering EBT in differential diagnosis of axillary masses and the need for tailored treatment strategies in such settings.