Florid papillomatosis of the nipple: immunohistochemical and flow cytometric analysis of two cases.

The immunohistochemical and DNA profiles of two cases of florid papillomatosis of the nipple (FPN) were compared with the immunohistochemical and DNA profiles of mammary intraductal carcinomas (IC) to assess the relationship between these two proliferative neoplasms. Both examples of FPN were circumscribed papillary tumors in the subareolar breast that showed cytologic atypia, intraductal necrosis, and a distinct myoepithelial cell layer. An antibody to muscle-specific actin (MSA) decorated a continuous myoepithelial layer in one case that was confirmed by electron microscopy. MSA showed patchy, discontinuous staining of apparent myoepithelium in the ICs. Flow cytometric analysis showed that both FPN lesions were diploid, rapidly proliferating lesions with S-phase fractions of 10.9% and 34.4%. One IC was aneuploid, and the five diploid neoplasms showed S-phase fractions ranging from 6.4 to 15.8%. In FPN many epithelial cells stained intensely for S-100 protein, but each IC also showed at least focal expression of S-100 protein. One case of FPN was focally positive for gross cystic disease fluid protein 15 (GCDFP-15), but neither stained for tumor-associated glycoprotein-72 (TAG-72) nor for the product of the c-erbB-2 oncogene. In comparison, three ICs expressed focal GCDFP-15, four stained for TAG-72, and one was positive for the c-erbB-2 oncogene product. These preliminary observations suggest that the tandem proliferation of epithelial and myoepithelial cells and the preservation of a normal structural relationship between the two appears to separate FPN from intraductal carcinoma.(ABSTRACT TRUNCATED AT 250 WORDS)