[Case of carcinoid tumor of the breast].

A 74-year-old female with a left breast mass was admitted to the Cancer Institute Hospital and underwent mastectomy. Upon study of a frozen section, a diagnosis of breast carcinoma was made. Histopathological examination revealed a non-invasive tumor whose slightly eosinophilic rich cytoplasm was positive for PAS and Alcian-green staining and argyrophilic staining. The tumor showed medullary arrangement, partly with glandular and rosette-like structures. Electron microscopically, many dense core granules (170 +/- 30 nm in diameter) were diffusely distributed in almost all the tumor cytoplasm, they were thought to be neurosecretory granules. A diagnosis of mucocarcinoid of the breast was made. The patient experienced no dyshormonal disorder during the course of the disease and is alive and well without recurrence.