Isoenzyme pattern of enolase in the diagnosis of neuroendocrine bronchopulmonary tumors

Electrophoretic separation of enolase isoenzymes and the measurement of enolase activity were performed in 25 lung tumor extracts. In 13 neuroendocrine (NE) tumors (nine small cell lung carcinoma [SCLC], three atypical NE tumors, and one carcinoid tumor), the NE differentiation was assessed by ultrastructural determination of neurosecretory granule (NSG) density. Twelve non‐NE lung tumors also were studied (three adenocarcinomas, four epidermoid, two composite, two large cell undifferentiated carcinomas, and one lymphoma). Four normal lung tissues and 1 human brain were used as controls. The γγ isoenzyme was present at a high level (mean ± SE, 12 ± 3%) in all NE carcinomas and consistently absent in all non‐NE tumors as well as in normal lung. The αγ isoenzyme was found in significantly higher proportion in NE carcinomas (mean ± SE, 29 ± 2%) than in non‐NE tumors (mean ± SE, 8 ± 1%) (P