Epithelioid Hemangioendothelioma Arising Within Mediastinal Myelolipoma: A WWTR1-Driven Composite Neoplasm.

In this article, we describe a case of conventional epithelioid hemangioendothelioma (EHE) arising within an extra-adrenal myelolipoma. This composite neoplasm arose in the mediastinum of a 51-year-old female. The tumor was composed of a large myelolipoma that contained nodules of EHE consisting of CD31-positive epithelioid endothelial cells that grew in solid cords and were enmeshed in a basophilic hyalinized stroma. Both EHE and myelolipoma are characterized genetically by alterations of WWTR1. We demonstrated the expression of CAMTA-1 chimeric protein by immunohistochemistry both in the neoplastic endothelial cells of EHE and some of the endothelial cells lining the blood vessels in the myelolipoma. To the best of our knowledge, this is the first report of a malignant vascular neoplasm arising in association with myelolipoma.