Epithelioid hemangioendothelioma. Report of a case with immuno-lectinhistochemical and ultrastructural demonstration of its vascular nature.

The epithelioid hemangioendothelioma (EHE) is a rare vascular tumour of borderline malignancy, first described as a separate entity in 1982 by Weiss and Enzinger. The abundant cytoplasm of endothelial cells mimiking epithelioid appearances, prominent cytoplasmic vacuolization and barely perceptible lumina even in reticulin stains may result in EHE being mistaken for a signet ring cell carcinoma. In our case, difficulties in differential diagnosis were enhanced by the location of the tumour within an inguinal lymph node. The usefulness of FVIIIR: Ag- and UEA I- histochemistry in ascertaining the endothelial nature of this tumour is demonstrated, in correlation with electron microscopic data. The different reaction sites of these markers are striking and typical: FVIIIR: Ag displays a granular or diffuse cytoplasmic reaction, whereas UEA I provides a linear staining of vacuoles and luminal surfaces.