ABSTRACT
Carcinoid tumors were first described by Lubarsch in 1888 (1), who found multiple tumors in the distal small bowel of two patients at postmortem examination. However, the term karzinoide was not adopted until proposed by Obendorfer in 1907 when he described small bowel tumors that behaved in a more indolent fashion than conventional gastrointestinal carcinomas (2). Carcinoid tumors can arise in any gut-related organ, including the lungs and bronchus (3). Carcinoid tumors arise from neuroendocrine cells, and are characterized by positive reactions to silver stains and neuroendocrine markers including neuron-specific enolase, synaptophysin, and chromogranin (3). Histologically, carcinoid cells contain numerous membrane-bound secretory granules which contain a number of peptide hormones and biogenic amines. These substances include serotonin, which is metabolized to 5-hydroxyindole acetic acid (5-HIAA) and excreted in the urine. Carcinoid tumors have been found to also secrete corticotrophin, histamine, dopamine, substance P, neurotensin, prostaglandins, kallikrein, vasoactive intestinal polypeptide (VIP), gastrin releasing polypeptide (GRP), calcitonin, gastrin, and pancreastatin (3,4).
