Electron microscopy in small cell lung carcinomas: clinical correlation.

Abstract

In order to investigate the relationship of subcellular differentiation of small cell lung carcinomas (SCLC) and clinical response, we reviewed the electron microscopic (EM) features of tumor biopsy specimens from 33 patients with SCLC diagnosed by light microscopy (LM). These tumors were divided by EM into four groups according to the ultrastructural features. Group I (13 patients) had tumors with only neurosecretory granules on EM. Group II (11 patients) had tumors with neurosecretory granules and other subcellular features of non-SCLC. Group III (five patients) had tumors that lacked neurosecretory granules but contained subcellular features of non-SCLC. Group IV (four patients) had tumors that lacked all of these features. The complete and partial response rate to systemic chemotherapy with or without radiation therapy was 88% in the total population studied. The response rates were not statistically different in any of the four groups based on EM findings. The results of this study suggest that the LM diagnosis of SCLC alone adequately identifies lung cancer patients with a high response rate to systemic therapy.