A case of male invasive lobular carcinoma arising from an accessory breast

Abstract

A 73-year-old man presented with a firm mass accompanied by a skin-rash located in the left axillary region. Mammography, ultrasonography, and CT scan showed no evidence of tumors in the mammary glands. A skin biopsy revealed a poorly differentiated adenocarcinoma. The immunohistochemical analyses showed that the tumor cells were positive for estrogen receptor and gross cystic disease fluid protein-15, but were negative for E-cadherin. Invasive lobular carcinoma was diagnosed, and tumor resection with left axillary lymph node dissection was done. The tumor measured 3.0 cm, and there was no evidence of lymph node metastasis. Postoperative histological findings indicated the presence of mammary gland tissue components that were partially infiltrated by tumor cells. The final diagnosis was invasive lobular carcinoma originating from the accessory breast. He was given tamoxifen and has survived, so far, disease-free for 6 months after surgery.