Bronchial carcinoid appearing as a breast mass.

Carcinoid tumors of the breast are extremely rare. We studied what is to our knowledge the second case of an extramammary carcinoid presenting initially as a breast mass. Varying degrees of ribbon, trabecular, acinar, and insular patterns were present in the primary bronchial tumor and in several secondary deposits, including the initial breast lesion. The cells were argyrophilic and contained round and membrane-bound electron-dense granules. Estrogen and progesterone receptors were present in a cerebral metastasis. Polypeptide hormones and 5-hydroxytryptamine were not detected by immunocytochemistry.