Neuroendocrine phenotype of non-small cell lung carcinoma: immunohistological evaluation and biochemical study.

AIMS AND METHODS: The prevalence and distribution of neuroendocrine differentiation in non-small cell lung cancer (NSCLC) was estimated by assays for synaptophysin (SYN), chromogranin A (CgA), Leu7 and neuron-specific enolase (NSE). Serum NSE and CgA were determined in parallel to find the values of these markers for distinguishing neuroendocrine differentiation in NSCLC. Fifty-eight resected NSCLC specimens and 34 sera of NSCLC patients entered the study. Neuroendocrine differentiation was graded according to the percentage of neuroendocrine tumor cells as NE0--0%, NE1-NE4--1%->76%. Serum NSE <12.5 ng/mL and serum CgA <46 U/L were taken as cutoff levels.
RESULTS: 63.8% (37/58) of NSCLC were scored as NE1-NE4 according to the SYN, CgA and Leu7 levels; 34.5% as NE1; 29.3% as NE2-NE4. 56.8% of tumors were positive for SYN, 34.4% for CgA, 22.4% for Leu7, and 79.3% for NSE. A significant relationship was found between tumor SYN and tumor CgA expression, and between tumor SYN expression and tumor stage. Adenocarcinomas showed a significantly higher rate of neuroendocrine differentiation than squamous cell carcinomas. All normal serum CgA levels corresponded to a lack of CgA expression in the tumors. The increased serum NSE levels presented by 26% of NSCLC patients (mainly <16 ng/mL) did not correlate with tumor NSE expression.
CONCLUSIONS: The prevalence of neuroendocrine differentiation in NSCLC varies and depends on the immunohistochemical criteria used; this warrants standardization of the immunohistochemical criteria for neuroendocrine differentiation in NSCLC. NSE expression in the tumor and a mild increase in serum NSE are poor markers for distinguishing neuroendocrine differentiation in NSCLC.