Endocrine tumors of the ileum. Cytochemical and clinical aspects.

Sixteen patients with endocrine ileal tumors and liver metastases were analyzed with regard to the size, multicentricity, and growth pattern of the primary tumor, the occurrence of carcinoid syndrome, as well as the concentrations of serotonin and substance P (SP) in blood, 5-hydroxy-indole-acetic acid (5-HIAA) in urine, and the course of the disease. Excised specimens from the tumors were immediately processed for immunocytochemical investigations of the presence of neurohormonal peptides, using a broad spectrum of antisera and optimal histoprocessing techniques. In all patients the serotonin levels in blood and/or the 5-HIAA in urine were high. The SP concentration in plasma was markedly elevated in all but two of the ten patients investigated in this respect. A mixed growth pattern prevailed in the tumors of 7 patients with fatal disease. Serotonin cells were found in all tumors and SP-immunoreactive tumor cells in all but one; one of the carcinoids also contained a few tumor cells displaying enkephalin immunoreactivity. In conventionally fixed and paraffin embedded specimens of the same tumors usually no immunoreactive tumor cells at all could be demonstrated, showing that SP is among the peptides vulnerable to poor histotechniques. Nevertheless, SP, together with serotonin, constitute reliable clinical tumor markers for ileal carcinoids.