Primary small cell neuroendocrine carcinoma of the mediastinum: computed tomography and histopathological correlation

The objectives of this study were to describe the computed tomographic (CT) and histopathological characteristics of neuroendocrine carcinomas of the mediastinum and to improve the diagnostic accuracy for these tumors.

We retrospectively analyzed 9 patients with histopathologically confirmed primary small cell neuroendocrine carcinoma of the mediastinum.

Of the 9 tumors, 6 (67%) were located in the anterior-middle mediastinum; 2, in the anterior-middle-posterior mediastinum; and 1, in the middle-mediastinum. Eight tumors appeared inhomogeneous on CT, with large areas of necrosis, whereas 1 tumor had a uniform density. Four tumors (44%) had scattered punctate calcifications. Moderate, heterogeneous enhancement (range, 21-34 Hounsfield units) was present in 8 patients. All tumors compressed or invaded the adjacent mediastinal structures. Hematoxylin and eosin staining results revealed small tumor cells, with little cytoplasm, pale chromatin, and inconspicuous or absent nucleoli. Immunohistochemical analysis results showed that the tumor cells were positive for chromogranin A, synaptophysin, and neuron-specific enolase.

A large tumor located in the anterior-middle mediastinum, showing scattered punctate calcifications and compressing or invading the adjacent mediastinal structures, should arouse suspicion for a small cell neuroendocrine carcinoma. However, the diagnosis of such tumors requires a combination of pathological and immunohistochemical examination.