CD10 Is Expressed in Most Epithelioid Hemangioendotheliomas: A Potential Diagnostic Pitfall

Context. —Epithelioid hemangioendothelioma (EHE) is a vascular neoplasm that occasionally is difficult to distinguish from primary/metastatic carcinomas, particularly when EHEs express keratins. We recently encountered an EHE with strong CD10 positivity mimicking renal cell carcinoma. Objective. —To examine sensitivity and specificity of CD10 in EHE. Design. —Nine EHEs were stained with keratins, factor VIII, CD31, CD34, and CD10. Mimics of EHE were also retrieved and stained with CD10. Results. —The EHE patients included 5 men and 4 women. Patients ranged in age from 24 to 74 years. Tumors were located in liver (3), skin (2), lung/pleura (2), and sternomastoid and mediastinum (1 each). Two had skin metastases. All EHEs were positive for vascular markers. A total of 7 of 9 primary tumors expressed cytoplasmic and intracytoplasmic luminal CD10. The 2 skin metastases were positive, whereas 2 primary skin EHEs were negative. Of the mimics, CD10 showed staining in 7 of 23 cases: 3 of 3 renal cell carcinomas, 1 of 7 other carcinomas, 2 of 3 epithelioid angiosarcomas, 1 of 3 melanomas, 0 of 3 mesotheliomas, and 0 of 4 epithelioid hemangiomas. Conclusions. —CD10 has a sensitivity of 78% (confidence interval, 63.6%–92.4%) and specificity of 70% (confidence interval, 54%–85.9%) for EHE. There is a growing list of tumors that show expression of CD10. Pathologists should be aware of this diagnostic pitfall.