Mastopathy in insulin-requiring diabetes mellitus.

Diabetic mastopathy is a recently described collection of histopathological features found in dense fibrous breast masses in insulin-requiring diabetics. Fifty-seven breast biopsy specimens showing nonspecific benign disease were examined in a blinded fashion from 21 diabetics (seven insulin-requiring, 14 non-insulin-requiring), 30 age-matched controls and six patients with thyroid disease. Five diabetics had the constellation of extensive keloidal fibrosis, mononuclear perivasculitis, and mononuclear ductitis and/or lobulitis, whereas none of the controls or patients with thyroid disease had all of these features. All five patients with diabetic mastopathy were insulin-requiring (two type I, three type II). Epithelioid fibroblasts in the stroma, a previously described component of this constellation, were present in three of the five cases but do not appear to be essential in making the diagnosis. Four of the five diabetics were hypertensive, and three had secondary diabetic complications. The mean duration of diabetes in the five patients was greater than 13 years. Based on a previous report and the current study, this constellation of histological features appears to be relatively specific for insulin-requiring diabetes mellitus. The single clinical factor common to all patients with diabetic mastopathy in this article and in a previous study was exogenous insulin use.