Lobular carcinoma of the male breast.

BACKGROUND: A case of lobular carcinoma in a male breast is described. Lobular carcinoma is a very uncommon histopathologic form of male breast cancer because of the absence of lobules in the normal male breast. The cytoarchitecture of the normal male breast can be deranged in conditions such as Klinefelter's syndrome or as a result of estrogen exposure. Lobular carcinoma of the male breast has been described in such instances where cytoarchitectural changes are likely to have occurred. METHODS AND RESULTS: After the pathologic diagnosis was made, a fibroblast karyotype was performed to confirm a male genotype. The patient had received no hormonal therapy. The English language literature was reviewed. CONCLUSIONS: This case represents the first report of lobular carcinoma in a proven genotypic male patient receiving no exogenous estrogens.