Cancer of the male breast presenting as an axillary mass

The authors describe a 55-year-old man with an axillary mass. Physical examination of the breast was normal, and the patient had not risk factors for cancer of the male breast. A workup for other possible cancers was normal. Excisional biopsy of the mass revealed metastatic adenocarcinoma. The histology favored a primary breast cancer. The patient had a right modified radical mastectomy. The pathologic examination showed infiltrating ductal adenocarcinoma of the breast. Adjuvant therapy included combination chemotherapy followed by tamoxifen. Physicians must be aware of the differential diagnosis of an unknown primary cancer when it presents as an axillary mass.