Fine structure of a malignant hemangioendothelioma of the esophagus.

The histology and electron-microscopy of a malignant hemangioendothelioma of the esophagus wall appearing in a 42 year old male is presented. By light microscopy the tumor is composed of vessels and capillary-like structures of an anastomosing nature covered by atypical endothelial cells. These cells infiltrate the interstitial spaces growing into the posterior mediastinal area. Electron microscopy confirms the endothelial nature of the neoplastic cells, showing characteristics of the cell type, as is the presence of Weibel-Palade bodies, filaments and active pinocytosis. Hemangioendothelioma should be differentiated from other vascular tumors (angiosarcoma) as are hemangiopericytoma or hemangioblastoma, being composed exclusively of malignantly transformed endothelial cells.