['Thymidylate synthase (TS) expression has been reported in various tumors, including non-small-cell lung carcinoma (NSCLC), but not in high-grade neuroendocrine (HGNE) carcinoma of the lung.', 'We measured TS expression in surgically resected pulmonary tumors, comparing HGNE carcinomas of the lung (13 large-cell neuroendocrine carcinomas, 8 small-cell lung carcinomas) with squamous cell carcinoma and adenocarcinoma of the lung using laser-capture microdissection for tissue isolation, real-time polymerase chain reaction (PCR), and immunohistochemistry. We also measured TS mRNA expression in small-cell lung carcinoma (SCLC) and NSCLC cell lines using real-time PCR.', 'At both mRNA and protein levels, TS expression was significantly higher in squamous cell carcinoma compared to adenocarcinoma. Moreover, TS expression was significantly higher in HGNE carcinomas of the lung compared to squamous cell carcinoma. A significant correlation was found between mRNA and protein expression. TS mRNA expression in SCLC cell lines was significantly higher than in NSCLC cell lines.'] Does high-grade neuroendocrine carcinoma of the lung show increased thymidylate synthase expression compared to other histotypes?