Epithelial-to-mesenchymal transition (EMT) describes a phenotypical change induced in epithelial cells that lose their cell-cell basement membrane contacts and their structural polarity to become spindle-shaped and morphologically similar to mesenchymal/myofibroblast cell. The abnormal induction of EMT has been demonstrated to contribute to cancer dissemination and progression. Renal cell carcinoma (RCC) with sarcomatoid differentiation (sarcomatoid RCC) represents a good example of EMT both morphologically and immunohistochemically. Early spindle cell changes can at times be identified in RCC and likely represent an early step toward EMT. Herein, we present a review of the current understanding of EMT in renal neoplasms including some known signaling regulation, the association of sarcomatoid differentiation in RCC with aggressive behavior and dismal prognosis, and EMT-related tumor biology in sarcomatoid RCC. A better perception of the EMT may contribute toward an improved understanding of the development of sarcomatoid RCC. In addition, a distinct signature for sarcomatoid RCC may have utility in the differential diagnosis for prognostic stratification as well as in identifying novel genes and pathway targets for therapeutic intervention.