The argentaffin tumor of the gastrointestinal tract is no longer a medical curiosity. It has been recognized since 1888 that this tumor has malignant propensities. Indeed, such tumors occurring in the small bowel and appendix (in which locations they are commonest) were classified with the carcinomas (adenocarcinomas), and for many years it was difficult to single out, in a series of epithelial tumors, which ones were adenocarcinoma and which were the more benign argentaffin carcinoma.
However, they became recognized as a distinct pathological entity around the turn of the century, and the unfortunate name of "carcinoid" was applied. The reason for the consideration of these tumors as distinct from carcinoma was that the appendiceal tumors showed, in general, a benign course. But "carcinoid" of the appendix does metastasize; in 1926, Stewart and Taylor reported such a case and collected eight other cases of appendiceal argentaffinoma with metastases.1 Their case
ELDRED WJ. Argentaffin CarcinomasReport of Twenty-Nine Cases, Six Malignant. AMA Arch Surg. 1956;73(3):517-525. doi:10.1001/archsurg.1956.01280030143017