Anaplastic Sarcoma of the Kidney Presenting as a Polyoid Mass in the Renal Calyx: A Newly Recognized Entity with DICER1 Mutations

Summary: Anaplastic sarcoma of the kidney is a rare and newly recognized entity characterized by DICER1 mutations, with fewer than 30 cases reported to date. Loss of function mutations of DICER1 alter expression of micro RNAs that play a major role in regulating the cell cycle and are associated with tumor predisposition and progression. Anaplastic sarcoma of the kidney/DICER1 renal sarcoma is usually cystic and generally composed of a spindle cell proliferation showing marked cellular anaplasia, often with prominent areas of chondroid differentiation.