Male accessory breast cancer on the abdominal wall: a case report and literature review

Background: Accessory breast cancer is very rare, particularly in men. Male accessory breast cancer on the abdominal wall has not been documented in the scientific literature so far. We describe a case of male accessory breast cancer on the abdominal wall. Case presentation: We describe a male patient suffering a swelling and erosive, enlarged, and hardened abdominal wall mass with pain due to abdominal wall accessory breast cancer. The patient had no obvious disease history, and the initial clinical symptom was a small mass on the abdominal wall. B-ultrasound revealed a solid subcutaneous nodule in the right abdomen with a size of similar to 2.8 x 2.5 x 1.5 cm. The abdominal wall tumor resection was performed with local anesthesia. Pathological testing revealed a grade II infiltrating ductal carcinoma derived from the accessory mammary gland (right abdominal wall) with neuroendocrine characteristics, showing ER (100% strong positive), PR (100% strong positive), HER-2 (-), ki67 (40% positive), Syn (+), CgA (+), and GCDFP15 (+). Conclusion: Nonaxillary accessory breast cancer in males is very rare, with no obvious clinical manifestations, and could be easily ignored. This disease requires great attention from clinicians.