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.