Paget's disease of the nipple resembling an acantholytic disease on microscopic examination.

Two biopsies of an erosive lesion of the nipple had an appearance of an acantholytic disease without showing malignant cells. Only a third biopsy through the nipple with removal of a larger portion revealed some nests of atypical, large cells with clear cytoplasm, typical of Paget's disease. Immunohistochemical findings with carcinoembryonic antigen confirmed the diagnosis of Paget's disease of the nipple. This is the first case of Paget's disease which shows extensive acantholysis on microscopic examination and which resembles pemphigus vulgaris histologically. Acantholytic diseases are easily distinguished from Paget's disease and have never been mentioned in the differential diagnosis of this disease. A large biopsy through the nipple with the removal of a liberal portion of the nipple is suggested in every case of a suspected unilateral lesion of the nipple in order to avoid the overlooking of small nests of Paget's cells, as in our first biopsies, showing a histological picture of an acantholytic disease.