Clinical and Molecular Characteristics and Outcome of Cystic Partially Differentiated Nephroblastoma and Cystic Nephroma: A Narrative Review of the Literature

SIMPLE SUMMARY: Although renal tumors in children are mostly solid masses, cystic renal tumors also occur. The most likely diagnoses for cystic renal tumors include cystic partially differentiated nephroblastoma and cystic nephroma. Since these tumors are rare, limited information on the treatment, clinical and molecular characteristics, and outcome is available. In this review, we aim to summarize all reported patients with cystic partially differentiated nephroblastoma and cystic nephroma. We identified 113 cystic partially differentiated nephroblastoma and 167 cystic nephroma patients. Surgery was the cornerstone of treatment for both tumor types and chemotherapy was generally not recommended. Cystic nephroma was often related to DICER1-mutations and second tumors, whereas cystic partially differentiated nephroblastoma was related to somatic hyperdiploidy, although testing was rare. The outcome for both tumors is favorable. This study provides information for treatment decisions and stresses the importance of a central review of radiology and pathology, as well as referral to a clinical geneticist. ABSTRACT: In children presenting with a predominantly cystic renal tumor, the most likely diagnoses include cystic partially differentiated nephroblastoma (CPDN) and cystic nephroma (CN). Both entities are rare and limited information on the clinical and molecular characteristics, treatment, and outcome is available since large cohort studies are lacking. We performed an extensive literature review, in which we identified 113 CPDN and 167 CN. The median age at presentation for CPDN and CN was 12 months (range: 3 weeks–4 years) and 16 months (prenatal diagnosis–16 years), respectively. No patients presented with metastatic disease. Bilateral disease occurred in both entities. Surgery was the main treatment for both. Two/113 CPDN patients and 26/167 CN patients had previous, concomitant, or subsequent other tumors. Unlike CPDN, CN was strongly associated with somatic (n = 27/29) and germline (n = 12/12) DICER1-mutations. Four CPDN patients and one CN patient relapsed. Death was reported in six/103 patients with CPDN and six/118 CN patients, none directly due to disease. In conclusion, children with CPDN and CN are young, do not present with metastases, and have an excellent outcome. Awareness of concomitant or subsequent tumors and genetic testing is important. International registration of cystic renal tumor cohorts is required to enable a better understanding of clinical and genetic characteristics.