Introduction. Renal cell carcinoma (RCC) is a rare malignant renal tumor in children, which accounts for 2–4 % of pediatric and adolescent’s kidney malignancies. A number of recent studies have shown that RCC developing in pediatric age differs in the spectrum of histological variants, clinical course and prognosis from RCC in adult patients.

The aim of the study – retrospective analysis of the clinical and morphological characteristics of RCC, as well as the results of therapy of patients with a diagnosis verified in the Department of Pathology in Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology, Ministry of Health of Russia (Center).

Materials and methods. Retrospective analysis of patients with a histologically confirmed diagnosis RCC for the period 01.2012–05.2022 was done. During the specified period of time in the Department of Pathology in Center 42 patients with a confirmed diagnosis of RCC aged 0 to 18 years were registered. Out of 42 registered patients with RСС, 28 patients with known clinical data were included in this analysis, of which 11 patients underwent primary surgical treatment in Center. Demographic characteristics, clinical data, morphological variants of RCC, the volume of therapy performed, including the features of the performed surgical intervention were analyzed. The assessment of stage was carried out according to the TNM classification. Patients were treated according to the protocols of the SIOP-RTSG group (SIOP 93-01, SIOP-2001, SIOP-RTSG-2016). The analysis of the results was carried out on 01.06.2022.

Results. In the general group of patients (n = 42), the distribution by histological types was presented as follows: papillary type – in 16/42 (38.0 %), translocation type – in 12/42 (28.6 %), clear cell type – in 5/42 (11.9 %), chromophobic type – in 4/42 (9.5 %), RCC with succinate dehydrogenase deficiency – in 2/42 (4.8 %), translocation type in combination with papillary type – in 1/42 (2.4 %), tubulocystic type – in 1/42 (2.4 %), unspecified type – in 1/42 (2.4 %). A subsequent in-depth analysis was performed on a group of 28 patients. The median age at the time of diagnosis of RCC was 11.0 years (range – 3.0–16.9). The male:female ratio was 1.1:1. The median tumor volume (n = 27) was 44 cm3 (range 1.8–547.7 cm3 ). The clinical picture included palpable formation in the abdominal cavity (n = 5), intoxication syndrome (n = 5), pain (n = 4), enuresis (n = 1), macrohematuria (n = 1), in 12 cases the tumor was detected accidentally. The duration from the onset of the first symptoms/detection of the tumor to the diagnosis was 2.5 months (range 0.5–40.3 months). Distribution by clinical stages according to the TNM system: stage T1 – 22 (78.5 %) cases, T2 – 4 (14.3 %) cases, T3 – 1 (3.6 %), Tx – 1 (3.6 %) case. According to the results of postsurgical staging, the following distribution by stages N was noted: N0 – 15 (53.6 %) cases, N1 – 4 (14.3 %) cases, Nx – 9 (32.1 %) cases. Stage M0 – in 22 (79 %) patients, 6 (21 %) patients were not fully examined, the stage was treated as Mx, mainly due to the lack of data on osteoscintigraphy. It should be noted that proven distant metastases were not detected in any patient at the time of diagnosis. Preoperative polychemotherapy (PCT) without histological verification was performed in 9 (32.1 %) patients. When assessing the size of the tumor after preoperative PCT, a decrease in size was noted in 2 patients, the absence of size dynamics in 7 patients. Surgical treatment was performed in all patients. An initial thick-needle biopsy followed by surgery was performed in 6 (21.4 %) patients, 1 (3.6 %) patient underwent an initial laparoscopic biopsy of the affected retroperitoneal lymph node. In 1 (3.6 %) case, a biopsy was performed followed by chemotherapy. In 3 cases, the biopsy was uninformative and in 2 cases a second biopsy was performed. The primary surgery was performed in 11 (39.3 %) patients. R0 resection was achieved in 22 (78.6 %) cases, R1 resection was proved in 2 (7.1 %) cases, in 4 (14.3 %) cases the resection edges were not subject to evaluation (Rx). In 2 cases, complications of surgical treatment were noted: in 1 case, intraoperative tumor rupture, in 1 case – ischemic nephropathy after laparoscopic kidney resection. All patients were diagnosed morphologically in Center. Translocation RCC – 9 (32.1 %) cases and papillary RCC – 9 (32.1 %) cases prevailed in the group of 28 patients. The discrepancy of diagnoses/histological subtypes of RCC between the local pathomorphological laboratory and the reference in Center were noted in 7 (25 %) cases. The median follow–up of patients was 15.9 months (range 0.4–78.0 months). Of the 28 patients, 26 are alive (92.8 %). The progression of the disease was observed in 2 cases with the development of distant metastases in 1.6 and 12.8 months, these patients died.

Conclusion. RCC is a rare type of kidney tumor in children. Papillary and translocation variants of PCC are prevalent in the pediatric population. At the moment, radical nephrectomy with mandatory morphological examination of regional lymph nodes is considered as a standard treatment, while in some cases an organ-preserving operation may be considered. Interdisciplinary discussion of management tactics and surgical treatment in centers specializing in pediatric oncourology is mandatory.