KRAS and renal cell carcinoma: Papillary RCC is considered the classical papillary RCC morphology type I, albeit certain single entities with papillary features can be regarded as variants of papillary RCC or provisional entities like papillary renal neoplasm with reversed polarity (PRNRP), biphasic hyalinizing psammomatous RCC (BHP RCC), biphasic squamoid/alveolar RCC, or thyroid-like follicular RCC (TLF RCC) Some have a specific molecular driver alteration, for example, KRAS mutations in PRNRP, NF2 mutations in BHP RCC, and EWSR1-PATZ1 fusions in TLF RCC.