Pleural fluid neuron-specific enolase. A useful diagnostic marker for small cell lung cancer pleurisy.

We studied the value of pleural fluid neuron-specific enolase as a possible diagnostic marker for pleurisy of small cell lung cancer by using enzyme immunoassay. Pleural fluid NSE levels in 12 patients with carcinomatous pleurisy due to small cell lung cancer were compared with those in 37 patients with carcinomatous pleurisy due to non-small cell lung cancer and 39 patients with tuberculous pleurisy. The pleural fluid NSE level was elevated in nine of 12 (75 percent) patients with SCLC. However, only two of 37 (5 percent) patients with NSCLC and two of 39 (5 percent) patients with tuberculous pleurisy had an elevated pleural fluid NSE level. Moreover, none of ten SCLC patients with cytology-negative pleural effusions showed elevated pleural fluid NSE level. Thus, determination of pleural fluid NSE levels seems to be an effective means to differentiate carcinomatous pleurisy due to SCLC from that due to NSCLC, tuberculous pleurisy and cytology-negative pleural effusion in SCLC.