Solid and mucinous varieties of so-called mammary carcinoid tumors.

Three neoplasms that had histologic features reminiscent of carcinoid tumors of other sites were encountered in a review of 3,300 examples of invasive mammary cancer in women (.09%). One of these showed cytoplasmic argyrophilia. This, as well as the two putative carcinoids, lacked argentaffinity. Attention is directed to the occurence of variable numbers of argyrophilic cells in eight of 19 so-called mucinous cancers of the breast studied. Further, neurosecretory-type granules were observed in cells of all four mucinous cancers suitably prepared for electron microscopic examination. The possible reasons for the lack of universal argyrophilic reactions in these lesions is discussed. It is concluded that there may be two types of mammary carcinoid tumors, the solid and mucinous varieties. No patient who had the latter type had experienced treatment failure after five years of observation. Various numbers of ductal epithelial cells in four of 45 examples of banal fibrocystic disease showed cytoplasmic argyrophilia, and neurosecretory-type granules were found in two of eight examples suitably prepared for electron microscopic examination. Whether this demonstration establishes the existence of precursor elements for the development of the carcinoid tumors is at present uncertain.