Background Anaplastic sarcoma of the kidney (ASK) is a DICER1-related neoplasm first identified as a distinctive tumor type through the evaluation of unusual cases of putative anaplastic Wilms tumors. Subsequent case reports identified the presence of biallelic DICER1 variants as well as progression from cystic nephroma, a benign DICER1-related neoplasm. Despite increasing recognition of ASK as a distinct entity, the optimal treatment remains unclear. Methods Individuals with known or suspected DICER1-related tumors including ASK were enrolled in the International Pleuropulmonary Blastoma/ DICER1 Registry. Additionally, a comprehensive review of reported cases of ASK was undertaken and data was aggregated for analysis with the aim to identify prognostic factors and clinical characteristics to guide decisions regarding genetic testing, surveillance, and treatment. Results Ten cases of ASK were identified in the Registry along with 37 previously published cases. Staging data, per Children’s Oncology Group guidelines was available for 40 patients: 13 were stage I, 12 were stage II, 10 were stage III, and 5 were stage IV. Outcome data were available in 37 cases. Most (38 of 46) patients received upfront chemotherapy and 14 patients received upfront radiation. Two-year event-free survival (EFS) for stage I-II ASK was 81.8% (95% confidence interval [CI]: 67.2-99.6%), compared with 46.6% EFS (95% CI: 24.7-87.8%) for stage III-IV ( p=.07). Two-year overall survival (OS) for stage I-II ASK was 88.9% (95% CI: 75.5-100.0%) compared with 70.0% (95% CI: 46.7-100.0%) for stage III-IV ( p=.20). Chemotherapy was associated with improved EFS and OS with hazard ratios of 0.09 (95% CI: 0.02-0.31) and 0.08 (95% CI: 0.02-0.42), respectively. Conclusion ASK is a rare DICER1-related renal neoplasm. In the current report, we identify clinical and treatment-related factors associated with outcome including the importance of chemotherapy in treating ASK. Ongoing data collection and genomic analysis are indicated to optimize outcomes for children and adults with these rare tumors.