Breast carcinoma is a rare disease in men. The incidence is 1 per cent of the incidence in women. Relative hyperestrogenemia and environmental factors seem to be important for the development of the disease. In recent years, germline mutations have been observed in male breast carcinoma patients in several genes, BRCA2, the androgene receptor gene and PTEN. Suspected genetic factors include the cell-cycle checkpoint kinase (CHEK)2 protein truncating mutation 1100delC that has been shown to confer a 10-fold increase of breast cancer risk in men. The c.1-34T > C 5' promoter region polymorphism in cytochrome P450c17 (CYP17), a key enzyme in the biosynthesis of estrogen, has been associated with male breast cancer risk, hemochromatosis gene (HFE) mutations, the mismatch repair genes (hMSH2, hMLH1,hPMS1,hPMS2) and PTEN mutations (Cowden syndrome) are associated with male breast cancer. The majority of tumors is seen retromamillarly. Ductal carcinoma in situ comprises 5-10 % of all cancers. In case of invasive growth, 85-90 % are invasive ductal carcinomas (NOS), 2.5 % are papillary tumors; lobular cancers are exceptionally rare. About 3/4 of all cancers express estrogen and progesterone receptor with increasing positivity with increasing patient age. HER-2 / neu overexpression is seen in the same frequency as in female breast cancer. Poor prognostic factors are tumor size > 2 cm, poorly differentiated tumors, receptor negativity, axillary lymph node involvement and more than four affected nodes.