Clinical-Pathological Features of an Occult Mixed Mucinous Male Breast Cancer: A Case Report

Mucinous carcinoma of the male breast is an uncommon malignant breast neoplasm and its diagnoses remain difficult. It is probably due to such a low rate of breast cancer cases that men tend to be diagnosed at an older age than women and with a later stage of the disease. We describe a case of a 69-year-old male who displayed a palpable lump in his right axilla several years ago, showing signs of cutaneous adnexal mucinous adenocarcinoma after biopsy. After six years and several clinical examination and systemic investigation without results, the patient underwent to fine needle aspiration cytology and subsequently a biopsy of a mass with irregular margins in the retroareolar region of his right breast. The final diagnosis was of a mixed mucinous breast cancer with neuroendocrine differentiation. The tumor cells phenotype showed Synaptophisin (+), CEA (+/-), CK-20 (-), CK-7 (+), TTF-1 (-), estrogen receptor (-), progesterone (-) and HER 2 (++). These results were unusual for a mucinous male breast carcinoma. In the presence of a lesion in the axillary area with no specific primary origin, breast cancer should never be ruled out, even in the absence of clinical evidence and with an immunohistochemical pattern not indicative of mammary origin.