High-grade neuroendocrine carcinomas (NECs) are aggressive tumors with limited treatment options. Recently, studies have observed that the tyrosine kinase receptor CD117 is often overexpressed in this malignancy. As a result, CD117 has been identified as a target for therapy via the small molecule, tyrosine kinase inhibitor imatinib mesylate. In the present study, 17 low-grade, 4 intermediate-grade, and 76 high-grade NECs were immunostained for CD117, Ki-67, and p53. Overexpression of the three markers was mainly, but not exclusively seen in the high-grade NECs. Patients with overexpression of CD117 and p53 and increased Ki-67 expression showed reduced survival. However, no difference in survival was observed when the same analysis was applied solely to small cell lung cancer patients, the largest subset studied. These findings suggest that overexpression of CD117, p53, and Ki-67 reflects tumor grade and predicts survival in NECs, but fail as prognostic markers in the subset of small cell lung cancer patients.

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