Neuroendocrine neoplasms of the mediastinum.

Neuroendocrine neoplasms of the mediastinum form part of a family of tumors characterized by genotypic, immunophenotypic, and functional properties of neuroendocrine differentiation. Although rare, these tumors have been the source of much attention and controversy in the literature. Their nomenclature and classification, in particular, have continued to evolve over the years. Such tumors comprise lesions derived from neuroendocrine elements within the thymus, from paraganglionic rests, or from misplaced embryonal structures within the mediastinum. The most common neuroendocrine neoplasms of this anatomic region, however, correspond to neuroendocrine carcinomas of the thymus. The light microscopic, immunohistochemical, and ultrastructural features of these tumors are reviewed along with the advances in our understanding of these lesions and current trends in nomenclature and terminology.