Small cell carcinoma of the lung: serum calcitonin and serum histaminase (diamine oxidase) at basal levels and stimulated by pentagastrin.

Investigations were performed to evaluate the incidence of increased serum calcitonin and histaminase in 79 patients with untreated small cell carcinoma of the lung (SSC). In addition, serum calcitonin was measured following pentagastrin stimulation in 19 of these patients. Serum calcitonin was elevated in 54 of 79 patients (68%), 20 patients (25%) having a level usually associated with the diagnosis of medullary carcinoma of the thyroid (MCT). The levels of histaminase, on the other hand, did not differ from the distribution in normals. In three of 19 patients undergoing the pentagastrin stimulation test, calcitonin was significantly increased. Thus, serum calcitonin is frequently elevated in patients with SCC and a positive pentagastrin test is not pathognomonic of MCT.