The differential diagnosis included papillary RCC (excluded by the presence of mucinous stroma and absence of papillary architecture), sarcomatoid RCC (excluded by the lack of high-grade nuclear pleomorphism), mesenchymal tumors (rarely positive for cytokeratins), oncocytoma and chromophobe RCC (typically CD117-positive), and neuroendocrine neoplasms (excluded by negative chromogranin staining) [17,18]. Here, KIT is linked to mesenchymal cell neoplasm.