TUBULAR ADENOMA OF THE BREAST - AN IMMUNOHISTOCHEMICAL STUDY OF 10 CASES

Ten cases of so-called ''tubular'' adenoma and six cases of fibroadeno ma of the breast have been investigated with an immunohistochemical te chnique with the aim of providing both more details on their immunophe notype and of ascertaining the possible relationships between tubular adenoma and fibroadenoma. Smooth Muscle Actin, Cytokeratin 14, GFAP, S -100 Protein and Vimentin immunoreactivity have clearly demonstrated t hat cells with myoepithelial immunophenotype are one of the major cell components in breast adenomas. Epithelial Membrane Antigen (EMA), Hum an Milk Pat Globule II (HMFG II), Estrogen and Progesterone receptors have been detected in adluminal epithelial cells exclusively. Furtherm ore, Smooth Muscle Actin and Vimentin highlighted an abundant myofibro blastic component, intermingled with tubular structures in both tumor types. A low percentage (10-22%) of adluminal cells and of myofibrobla sts showed Ki-67 immunoreactivity in tubular adenomas and in fibroaden omas, whereas only rare myoepithelial cells demonstrated Ki-67 positiv ity in both tumor types. These data seem to indicate that several cell components of both epithelial and mesenchymal origin (epithelial cell s, myoepithelial cells, myofibroblasts) are involved in the genesis of tubular adenomas. The morphological and immunohistochemical features of tubular adenomas closely resemble, in some areas of the tumors, tho se of fibroadenoma. Therefore, they may represent histogenetically rel ated neoplasms with exuberant ductular component in tubular adenomas a nd predominant stromal component in fibroadenoma.