Most patients had little to no TPH1 and its product serotonin in their tumor samples, while nearby normal tissue displayed TPH1-positive cells (Fig. 3E,F), which are secretory epithelial cells specialized in producing serotonin (Bornstein 2012; Gershon 2012; Baganz and Blakely 2013), named enterochromaffin cells (ECs) (Supplemental Fig. S2C,E). The gene discussed is TPH1; the disease is neoplasm.