Neuron-specific enolase in small-cell carcinoma of the lung: the value of combined immunocytochemistry and serum determination.

The value of neuron-specific enolase (NSE) as a marker for small-cell carcinoma of the lung has been the subject of several reports. Taken together, about 70 per cent of patients with small-cell carcinoma had a raised serum concentration of NSE, and in a majority of patients NSE could be detected immunocytochemically in tumor biopsy speciments. This study examined the diagnostic value of combined immunocytochemical detection and serum determination of NSE in 96 unselected patients with small-cell carcinoma. Seventy-one patients had raised serum concentrations and in 69 a positive immunoreaction for NSE was demonstrated in the biopsy cells. However, for 87 (91%) of the patients, both or either of the NSE assays were positive. The combined use of immunocytochemistry and serum determinations thus gave better information on tumor NSE expression than either method alone. When patients with small or mechanically maltreated biopsy specimens were excluded, the accuracy of the combined assays was even higher (47/49, 96%). We therefore conclude that NSE, although not a specific marker for small-cell carcinoma of the lung, is useful as a complement to conventional diagnostic procedures and, when assayed both in biopsy material and in patient sera, tumor NSE expression can be demonstrated with a high precision.