Metastatic epithelioid hemangioendothelioma in a pleural effusion: diagnosis by cytology.

Epithelioid hemangioendothelioma (EH) is a vascular neoplasm of uncertain malignant potential. We report a 22-yr-old female with a primary malignant EH of the iliac bone with adjacent soft tissue involvement which, during its metastatic course, presented as a pleural effusion. The effusion was cellular with tumor cells present both singly and in clusters. Distinguishing cytologic features included cytoplasmic vacuolization consistent with primitive intracytoplasmic lumen formation, variability in cell size, biphasic cytoplasmic staining with Diff-Quik stain, multinucleation, cell in cell engulfment, and multiple prominent nucleoli. Differential diagnosis based on morphology included malignant mesothelioma and adenocarcinoma. Immunocytochemical stains on the neoplastic cells were positive for Ulex Europaeus, Factor VIII-related antigen, and CD34, reflecting vascular differentiation and confirming the diagnosis of metastatic EH to the pleural cavity.