[Fibroadenoma of the breast with atypical clear-cell epithelial hyperplasia. Apropos of 7 cases. Immunohistochemical study].

We report 7 cases of unusual fibroadenomas of the breast. They are characterized by an exuberant cellular proliferation within the ductal lumens. They appear in young women from 20 to 40 years old. These lesions are histologically identical to those described by Azzopardi (1979) under the name of "Argyrophilic cells in fibroadenomas" and by Eusebi and Azzopardi (1980) and by Govoni (1981) and called "Lobular endocrine neoplasia in fibroadenoma of the Breast". An immunohistochemical study reveals a major positivity of these cells, in all cases, with Antikeratin Antibody (anti Kl1) and with Epithelial Membrane Antigen (anti EMA) proving the epithelial origin of these cells. There cells cannot yet be regarded as belonging to the neuro-endocrine group, because of the negativity, in all cases of Grimelius and Bodian stains, and of the very heterogeneous positivity observed with Neuron-Specific Enolase antibody (anti NSE) and with anti Human Natural Killer antibody (anti HNK). These cellular proliferations seem to us, on the microscopical point of view related to the atypical epithelial hyperplasias of the breast, and different from the in situ lobular carcinoma. Thus we propose to call these lesions "variant of the breast fibroadenoma" characterized by an atypical epithelial clear cell hyperplasia. The treatment of these lesions merely consists of a lumpectomy. Only one case is associated with an eleven years free of disease follow-up: a follow-up comprised between on to fifteen months is observed in the others cases. The knowledge of these benign lesions appears to us very important, to avoid improper treatment caused by an erroneous diagnosis of carcinoma developing in a breast fibroadenoma.