SOLID PAPILLARY CARCINOMA OF THE BREAST - A FORM OF INTRADUCTAL CARCINOMA WITH ENDOCRINE DIFFERENTIATION FREQUENTLY ASSOCIATED WITH MUCINOUS CARCINOMA

We report 20 examples of a distinctive form of intraductal papillary c arcinoma frequently associated with both mucinous carcinoma and infilt rating ductal carcinoma, not otherwise specified. All the patients wer e in the seventh decade of life or older. The clinical presentation an d macroscopic appearance suggested a benign lesion in most cases, The tumors grew in a solid papillary pattern and displayed low-grade cytol ogical features as well as intracellular and extracellular mucin. Endo crine differentiation was demonstrated by the Grimelius stain in 11 of 17 cases and by the chromogranin immunohistochemical technique in eig ht of 14 cases. Lymph node metastases were not observed, but pulmonary metastasis occurred in one case. All the tumors were positive for est rogen receptors. We postulate that these lesions are the preinvasive c ounterpart of mucinous carcinomas with endocrine differentiation.