Serum and tissue distribution of a fragment of cytokeratin 19 (cyfra 21-1) in lung cancer patients.

A sensitive and relatively specific tumoral marker for lung epidermoid carcinomas could be used to identify patients likely to benefit from new therapeutic protocols. The cyfra 21-1 fragment of cytokeratin 19 has raised much hope in this regard amongst both technologists and clinicians. In a study of 195 subjects, we have shown by means of a serum assay that the usual cut-off value for this marker (3.3 ng/ml) can be lowered to 1.5 ng/ml without loss of specificity, and with an increase in sensitivity. There was a good correlation between serum marker level and tumor extension, but though cyfra 21-1 was not predictive of the suitability of a patient for surgery. A decrease of cyfra-21-1 was observed after complete resection of the tumor. There was no relation between serum assay results and immunohistochemical findings.