EWSR1 and mesenchymal cell neoplasm: It is recurrent in several types of neoplasia such as mesenchymal tumors, in hyalinizing clear cell carcinoma of salivary glands, and, most recently, in a malignant epithelioid neoplasm with predilection for mesothelial-lined cavities.9, , , –13 The EWSR1-CREM fusion genes encode fusion proteins with an N-terminal EWSR1 transactivation domain and a C-terminal DNA-binding domain of CREM.14