Epithelioid hemangioendothelioma (EHE) is a rare medium-to-low-grade malignant vascular tumor characterized by vascular differentiation along with specific morphological and genetic alterations. Approximately 90% and 5% of EHE cases are associated with the WWTR1-CAMTA1 and YAP1/TFE3 fusion gene, respectively. Therefore, nuclear CAMTA1 protein expression is considered to be an effective marker for EHE diagnosis. However, the specificity and reliability of this approach have recently been put into question. The purpose of this study was to compare the detection of CAMTA1 expression in cases of EHE and histologic mimics using fluorescence in situ hybridization (FISH) and conventional protein immunohistochemistry via hematoxylin and eosin staining. Fifteen EHE and 37 histologic mimic samples were immunohistochemically stained with polyclonal anti-CAMTA1 antibody to evaluate the nuclear protein expression level of CAMTA1. In addition, 15 EHE samples and 10 vascular tumor samples were subjected to FISH to detect the WWTR1-CAMTA1 fusion gene. Histologically, EHE typically showed a mucous hyaline or cartilaginous stroma, often forming a primitive vascular lumen, and expressed vascular endothelial markers. Twelve of the 15 EHE samples showed positive nuclear CAMTA1 expression with immunohistochemistry, whereas six of the 37 histologic mimics showed positive nuclear expression. FISH detected a red-green signal fusion in 14 of the 15 cases of EHE, but in none of the 10 vascular tumors. These results indicate that CAMTA1 is an effective and useful EHE marker, but that FISH fusion gene detection has better diagnostic value and clinical significance.