What happened, in summary

An 82-year-old man was referred to a breast clinic after 8 months of redness over the left side of his chest and a painless mass in the left armpit. Examination found a fixed 8 × 7 cm axillary mass with red skin and a sinus draining clear fluid. No lump could be felt in either breast, and imaging did not identify a primary breast lesion.

The treatment team discussed chemotherapy and surgery with him. He preferred surgery and underwent a left modified radical mastectomy. During the operation, surgeons removed a large solid and cystic axillary tumor together with surrounding enlarged lymph nodes.

Pathology identified grade III invasive ductal carcinoma involving the breast and axilla. Four of 21 axillary lymph nodes contained cancer, and the pathologic classification was pT3N2Mx. The tumor was negative for estrogen receptor, progesterone receptor, and HER2, making it triple-negative. It was CK7 positive and negative for GCDFP-15 and GATA-3. After review by several pathologists, the findings supported occult male breast cancer: breast cancer presenting through axillary lymph-node disease even though no primary mass was visible in the breast.