Axillary Adenocarcinoma Mimicking Apocrine Carcinoma or Invasive Lobular Carcinoma of the Accessory Breast in a Male—A Case Report—

Abstract

A 63-year-old man observed a reddish and slightly elevated lesion (20 mm in diameter) in the right axillary, 3 years prior to presentation. He visited a dermatologist at our hospital, and the lesion was considered to be of low malignant potential. Therefore, he was only followed up with close observation and did not receive any treatment. The patient returned to the hospital following an increase in lesion size (70 mm in diameter). Based on excisional biopsy findings, the lesion was diagnosed as carcinoma. Computed tomography revealed enlarged axillary lymph nodes. We performed tumorectomy and axillary lymph node dissection for suspected accessory breast cancer or sweat gland carcinoma. Histopathological findings showed trabecular proliferation of tumor cells that lacked cohesiveness, and immunohistochemical analysis revealed tumor cells with negativity for E-cadherin and immunopositivity for HER2. Therefore, we suspected invasive lobular carcinoma, which could not be definitively diagnosed owing to lack of accessory mammary glands around the tumor. Sweat gland carcinoma was also considered in the differential diagnosis ; however, this possibility was ruled out based on negative E-cadherin expression in our patient. Based on the aforementioned findings and clinical course, the patient was diagnosed with an invasive lobular carcinoma of the right accessory breast in a male. Postoperatively, the patient received adjuvant chemoradiotherapy and has had no recurrence for 2 years.