Diabetic mastopathy: a distinctive clinicopathologic entity.

Insulin-dependent diabetics may manifest evidence of autoimmune diseases involving endocrine or other organs. Rare cases of a peculiar fibrous and inflammatory lesion of the breast in diabetic patients have been previously described; however, the pathologic and clinical features that uniquely characterize these cases have not been defined or distinguished from other chronic inflammatory and fibrosing conditions in the breast. We studied eight patients with breast masses and longstanding insulin-dependent diabetes and compared them with 36 nondiabetic or short-duration diabetic patients with fibrosis and chronic mastitis. The longstanding diabetic patients presented with clinical breast masses ranging in size from 2 to 6 cm. Six of the eight patients had documented diabetic nephropathy, retinopathy, or neuropathy. Pathologically, these lesions showed lymphocytic lobulitis and ductitis, lymphocytic vasculitis (predominantly B cell), and dense keloid-like fibrosis that in many cases (six of eight) contained peculiar epithelioid cells embedded in dense fibrous stroma. We have provisionally labeled these cells "epithelioid fibroblasts" (EFBs). Although the features of lymphocytic lobulitis, ductitis, and/or vasculitis may occasionally be encountered in nondiabetic breast biopsies, EFBs appear to be unique to the diabetic condition. Control cases of chronic mastitis in nondiabetic or short-duration diabetes patients failed to show the complete constellation of lymphocytic lobulitis and ductitis, vasculitis, keloidal fibrosis, and EFBs. Diabetic mastopathy may represent an immune reaction to abnormal matrix accumulation. A hypothesis is presented.