"Diabetic mastopathy" in the male breast--a special type of gynecomastia. A comparative study of lymphocytic mastitis and gynecomastia.

Focal B-lymphocytic mastitis and focal fibrosis of the breast in young women have rarely been reported as a complication of longstanding insulin-dependent diabetes mellitus type I. We present two cases of "diabetic mastopathy" in male diabetics suffering from gynecomastia. Furthermore, these two cases were examined in comparison to a selected group of 6 patients showing gynecomastia with a marked inflammatory reaction, as well as to 24 non-selected cases of common gynecomastia. The lesion is interpreted as a diabetes-induced autoimmune reaction of the breast and may be regarded as a lympho-epithelial lesion. Its histopathological characteristics are a marked chronic periductal and perivascular mastitis with a predominance of B-lymphocytes, a focal homogenous fibrosis and so called "epithelioid stromal fibroblasts" within the fibrotic matrix. Our findings support the existance of "diabetic mastopathy" in the male and point out to the potentially misleading pattern of this benign tumor-like lesion simulating gynecomastia.