TFE3 and neoplasm with perivascular epithelioid cell differentiation: In addition to renal carcinomas, TFE3-fusions are also implicated in the pathogenesis of a subset of potentially aggressive mesenchymal tumors called perivascular epithelioid cell tumors (PEComas), which are derived from an unknown cell-of-origin, and most frequently occurring in the kidney in addition to other sites such as bladder and colon3.