Nodular sclerosing adenosis (adenosis tumor) of the breast. An immunohistologic study particularly in reference to the relationship with radial cicatrix and to the differential diagnosis with tubular carcinoma

The clinical and pathologic findings of four cases of palpable sclerosing adenosis of the breast, called "adenosis tumor", are reported. Adenosis tumor is a rare lesion that clinically and sometimes histologically is misinterpreted as mammary carcinoma. In our study, adenosis tumor was detected in four women of 35-39 years (average 37 years). All cases were treated by local excision. None of the lesions had recurred at follow-up, 1-3 years later. Microscopically the most frequent growth pattern was classical sclerosing adenosis. Other findings were epitheliosis, collagenous spherulosis, microcysts, apocrine metaplasia and radial scars. Only in one case were detected foci of lobular carcinoma in situ. With immunoperoxidase staining, the proliferating cells stained positively for cytokeratin (AE1/AE3) and actin, revealing epithelial and myoepithelial differentiation. Coexpression of actin, S-100 protein and GFAP was detected in numerous stromal myofibroblast-like cells. In sclerosing adenosis and in radial scar the tubules were surrounded by a continuous intact basement membrane composed of type IV collagen, whereas in tubular carcinoma basement membranes are almost entirely absent.