Pediatric cystic nephroma: clinical and molecular genetic characteristics
Authors: Teleshova M. V. , Yasko L. A. , Maslеnkova E. V. , Merkulov N. N. , Mitrofanova A. M. , Kurnikova M. A. , Manzhurtseva E. E. , Akhaladze D. G. , Tereshchenko G. V. , Perevozchikova N. G. , Shamin A. V. , Shamanskaya T. V. , Kachanov D. Yu. 
Published: December 2021

Cystic nephroma (CN) is a rare renal tumor occurring in children which belongs to a group of neoplasms linked with the inherited DICER1 syndrome. Given the rarity of CNs, it is important to describe clinical, radiological, and molecular genetic characteristics of these tumors in children and adolescents as well as to analyze treatment outcomes. We present our experience in managing 8 patients with histologically verified CN who received treatment and consultations at the D. Rogachev NMRCPHOI over a period of 9 years (2012–2020). The study was approved by the Independent Ethics Committee and the Scientific Council of the D. Rogachev NMRCPHOI. The patients’ parents gave their consent to the use of their child’s data, including photographs, for research purposes and in publications. We performed a retrospective analysis of clinical presentation, radiological findings, the extent of treatment given to patients, treatment outcomes, and the results of molecular genetic testing. The study included patients aged between 8.6 and 197 months at diagnosis (the median age was 14.2 months). The analysis of initial complaints revealed that six patients (75%) had an increased abdominal girth and a palpable mass in the abdomen, one patient (12.5%) presented with arterial hypertension, and another patient (12.5%) had a mass detected by a routine abdominal ultrasound examination. On contrast-enhanced computed tomography scans, CNs appeared as multicystic masses with thin, contrast-enhancing septa; the CN volume ranged from 59.7 to 1293.1 cm3 (the median volume was 626.3 cm3 ). In all cases, the diagnosis of CN was verified histologically. Surgical treatment included nephrectomy (n = 6) or partial resection of the affected kidney (n = 2) with the removal of the tumor. Some patients (n = 5) included in our analysis received pre-operative chemotherapy at the discretion of their treating physicians. Molecular genetic testing was carried out for 7 children: 4 out of 7 patients (57.1%) were found to have somatic and germline mutations in the DICER1 gene. Carriers of pathogenic DICER1 variant were identified in the family of 1 patient. The median duration of follow-up was 17.6 months (range: 1.7 to 58.9 months). Currently, all patients are alive, no relapses have occurred. Cystic renal neoplasms detected by radiological investigations should be reviewed at the reference centers for pediatric oncological diseases and included CN in the differential diagnosis. Initial surgery is the first line of treatment for cystic nephroma. The final diagnosis is made on the basis of a histological examination of tumor tissue. All patients with confirmed CN should be referred for genetic counseling and molecular genetic testing for germline mutations in the DICER1 gene and should receive surveillance recommendations for the early detection of other metachronous DICER1-associated tumors.