Pulmonary tumorlets associated with Cushing's syndrome.

Tumorlets of the lung generally have been considered benign nests of cells, usually found with bronchiectasis or fibrosis. We saw a patient with Cushing's syndrome whose tumorlets ultimately became roentgenographically visible as multiple small nodules throughout both lungs and metastasized to the mediastinum. The plasma corticotropin concentration was increased, as were the concentrations of corticotropin-like peptides in the tumor tissue. This experience lends support to the concept that some tumorlets arise from Kulchitsky's cells in the epithelium of peripheral bronchioles, as do carcinoid tumors, and have the same peptide-producing potential. The possibility of such tumors should be considered in patients with Cushing's syndrome who have no initial roentgenographic abnormality.