Non‐small cell lung carcinomas with neuroendocrine features. A light microscopic, immunohistochemical and ultrastructural study of 11 cases

Eleven resected primary lung carcinomas classified as large cell carcinomas or squamous cell carcinomas, but showing some microscopic resemblances to bronchial carcinoid and small cell carcinoma, were studied. All cases were neurone-specific enolase and protein gene product 9.5 positive, indicating neuroendocrine differentiation. Staining for bombesin, C-terminal peptide of human pro-bombesin and chromogranin was positive in some cases. Electron microscopy showed dense-core granules in six of seven cases investigated, the remaining case showing small granules of uncertain nature. All but one patient died within 15 months after operation. These data indicate that neuroendocrine differentiation in non-small cell carcinomas of the lung may in some cases be suspected on routine histology. The follow-up data suggest that the identification of these cases might have implications for prognosis and therapy, and consequently for diagnostic lung tumour classification.