Florid vascular proliferation associated with neural and neuroendocrine neoplasms. A diagnostic clue and potential pitfall.

We report the light microscopic and immunohistochemical features of vascular proliferations associated with 26 extracranial neural and neuroendocrine neoplasms including esthesioneuroblastoma, neuroblastoma/ganglioneuroblastoma, the primitive neural component of immature teratoma, mediastinal teratoma, primitive neuroectodermal tumor, intra-abdominal desmoplastic small cell tumor, Merkel cell carcinoma of the skin, and thyroid medullary carcinoma. These vascular proliferations were similar to those associated with high-grade glial neoplasms and were characterized by tufts of vessels with a glomeruloid configuration or by long cords of vessels. Immunohistochemical evaluation documented the presence of endothelial cells, perithelial cells, and basement membrane components within the foci of proliferating vessels. We propose that these vascular proliferations represent a characteristic feature of the neuroendocrine/neural neoplastic phenotype and that they possibly arise as the result of angiogenic factors produced by the neoplastic cells. The presence of these distinctive vascular lesions in the stroma of a poorly differentiated neoplasm should alert the pathologist to the possibility of the neoplasm being of a neural or neuroendocrine nature.