Neuroendocrine Lung Tumors

Abstract

Abstract: A case of large cell neuroendocrine carcinoma (LCNEC) of the lung is presented to introduce the topic of pulmonary neuroendocrine tumors. These encompass a spectrum of tumors including the low-grade typical carcinoid (TC), intermediate-grade atypical carcinoid (AC), and the high-grade LCNEC and small cell carcinoma (SCLC). These tumors have certain morphologic, ultrastructural, immunohistochemical, and molecular characteristics in common, but there are important differences in incidence, clinical, epidemiologic, histologic, survival, and molecular characteristics. Although these tumors are frequently discussed in a spectrum, the carcinoid tumors are only distantly related to the high-grade SCLC and LCNEC. In contrast to SCLC and LCNEC, both TC and AC can occur in patients with multiple endocrine neoplasia (MEN) type 1. In addition, neuroendocrine cell hyperplasia with or without tumourlets is relatively frequent in both TC and AC but not in LCNEC or SCLC. Histologic heterogeneity with other major histologic types of lung carcinoma occurs with both SCLC and LCNEC but not with TC or AC. In contrast to LCNEC, most TC and AC are readily diagnosed by light microscopy without the need for special tests. The percentage of genetic changes is usually low for TC, high for SCLC and LCNEC, and intermediate for AC.