Serotonin in cytologic samples of liver metastases of carcinoid tumors. An immunocytochemical study with a monoclonal antibody

Cytologic samples of malignant carcinoid tumors were examined with regard to the presence of serotonin by immunocytochemical staining with a monoclonal antibody. Serotonin immunoreactivity occurred in tumor cells derived from carcinoids of the small intestine while bronchial carcinoid tumor cells were nonreactive. Acetone-alcohol fixation of the cells was a prerequisite for an adequate staining. The serotonin-immunoreactive tumors were also argentaffin positive. The results indicate that cytologic specimens of neuroendocrine tumors, such as carcinoid, can be successfully assayed for the presence of serotonin by an immunocytochemical procedure.