Solitary breast metastasis: first manifestation of an occult carcinoid of the ileum.

A metastasis to the breast was the first manifestation of a clinically occult ileal carcinoid in a 53 year old woman. Modified radical mastectomy was perfomed after the breast neoplasm had been interpreted clinically and pathologically as a primary carcinoma. Permanent sections demonstrated the tumor to be composed of sheets of small uniform cells subdivided into lobules by delicate vascular septa. Silver impregnation revealed the presence of argentaffin cytoplasmic granules. This feature, with the added ultrastructural findings which showed pleomorphic neurosecretory-type granules within the cytoplasm of the tumor cells strongly suggested a metastasis to the breast from a midgut carcinoid. The subsequently performed barium study of the small bowel showed an infiltrating neoplastic lesion in the terminal ileum, which after surgical excision and histologic examination proved to be two typical argentaffin carcinoids with pleomorphic cytoplasmic granules. This report thus clearly demonstrates the importance of a combined light microscopic, histochemical and ultrastructural analysis of this breast neoplasm in order to establish its metastatic origin and to separate it from a primary carcinoma or a primary carcinoid of the breast.