Compared with smooth muscle tumors, PEComas have key features of eosinophilic to clear cytoplasm, round to oval nuclei, a prominent capillary network, and strong immunoreactivity for melan-A, HMB45, melanocyte-inducing transcription factor, and cathepsin K. Furthermore, PEComas commonly stain negatively for epithelial membrane antigen and cytokeratin, unlike epithelioid smooth muscle tumors. This evidence concerns the gene PMEL and neoplasm with perivascular epithelioid cell differentiation.