Immunohistochemistry of Neuroendocrine Neoplasms of the Bronchopulmonary Tract and Skin

Abstract

Bronchopulmonary neuroendocrine (NE) neoplasms encompass a wide spectrum of pathologically and clinically distinct entities which include typical carcinoids, well-differentiated NE carcinomas, and NE carcinomas of intermediate and small cell type (1,2). Typical carcinoids are predominantly centrally located. Microscopically they exhibit the classical architecture of solid cellular clusters and/or ribbons with little, if any, cellular pleomorphism. Metastases are very rare and appear only late in the course of the disease. Well-differentiated NE carcinomas have received various vague designations such as “atypical carcinoids”, and have sometimes been misinterpreted as “early oat cell carcinomas”. These tumors are most often peripheral and display considerable cytological pleomorphism; however, they still retain an organoid pattern (Fig. 1a). Mitotic figures are readily found but the mitotic activity is not as brisk as in NE carcinomas of intermediate or small cell type. Metastases are frequent. We have observed 2 to 5 years survival in about 50% of cases. NE carcinomas of intermediate and small cell type have a similarly aggressive course: they differ only in the size and arrangement of their cells. The NE carcinomas of intermediate cell type show solid clusters of pleomorphic cells with frequent central necrosis and peripheral palisading. The nuclei are vesicular and are at least twice the size of their small cell counterparts.