Case 27

A 60-year-old male was found to have pleural effusion and a pleural biopsy was performed.

What is the morphology impression and what stains you will do?

IHC

• CK5/6
• Calretinin
• MUC31
• Claudin 4

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Answer

This is a case of epithelioid hemangioendothelioma (EHE). The tumor cells will be positive for keratin, and various vascular markers. The specific marker here is CAMTA1. EHE has WWTR1-CAMTA1 fusion or YAP1-TFE3 fusion. Classic epithelioid hemangioendothelioma features cords or nests of epithelioid cells with cytoplasmic vacuolization within a myxochondroid or hyaline stroma. In contrast, epithelioid hemangioendothelioma with YAP1-TFE3 fusion presents as either solid growth or well-formed vascular channels lined by epithelioid endothelial cells showing moderate nuclear atypia and abundant pale cytoplasm.

References: https://tumourclassification.iarc.who.int/chaptercontent/33/73

Case credit: UCSD Pathology

Author: Wangpan Jackson Shi