A case of lobular carcinoma in a male breast is described. Because the stru
cture of the male breast does not have lobules and acini, lobular carcinoma
cases are seen infrequently. The pathological diagnosis was invasive lobul
ar carcinoma of the breast. The karyotype of the patient revealed a 46 XY/4
6 XY, dmin (double minutes) chromosomal structure. Although 28% of the exam
ined metaphases showed 46 XY, 1-5 dmin, the others were normal. We reviewed
the English literature and found 20 reported cases of lobular carcinoma of
the male breast. Our case represents lobular carcinoma in a proven genotyp
ic male patient showing no exogenous or endogenous estrogens.