Background. Langerhans cell histiocytosis (LCH) is a rare disease that occurs due to abnormal proliferation and expansion of myeloid precursors. The occurrence of mutations in genes that encode key kinases of MAPK-signaling pathway leads to its pathological activation and has been shown the cause of disease. Mutations in BRAF and MAP2K1 genes are the most frequent among LCH patients. The effectiveness of BRAF-inhibitors in LCH patients has been shown in numerous studies.

The purpose of the study – analyze the experience of BRAF-inhibitor vemurafenib administration as monotherapy and in combination with cytosine arabinoside (ARA-C) and 2-chloro-2'-deoxyadenosine (2-CdA) in pediatric patients with different forms of LCH.

Materials and methods. Fifteen patients with various forms of LCH were enrolled in the study. BRAF mutations were detected in 14 patients, mutation in the MAP2K1 gene was detected in one case. Patients with “risk organ” (RO) involvement were included in the first group (n = 9). These patients received combined therapy with vemurafenib and ARA-C/2-CdA. Patients without RO involvement, included in group 2 (n = 6), received vemurafenib as monotherapy. The assessment of the response to the therapy in group 1 was carried out in accordance with the DAS scale, in group 2 in accordance with the RECIST v1.1. The toxicity assessment in both groups was carried out in accordance with the CTCAE v5.0.

Results. All patients in group 1 achieved non-active disease status with a median of 35 (28–61) days. In group 2 partial response to vemurafenib was achieved in 5 cases. Relapse after targeted therapy termination was diagnosed in two patients. Photodermatitis was the most common side effect of targeted therapy.

Conclusions. The use of vemurafenib was effective in both groups. There were no cases of grade III–IV toxicity according to CTCAE v5.0 associated with vemurafenib administration in this study. The combination of vemurafenib and ARA-C/2-CdA showed high efficacy and good tolerability in group 1. Two cases of disease relapse after targeted therapy cessation in group 2 show that the monotherapy approach does not always allow to achieve long-term remission in LCH patients.

According to several observations, up to a third of post-transplant relapses in childhood acute leukemia are associated with the loss of heterozygosity of the major histocompatibility complex (HLA). Furthermore, the inefficacy of the graft-versus-leukemia reaction, as evidenced by the lack of therapeutic effect from the infusion of donor lymphocytes, indicates the need for timely detection of this marker to change the treatment strategy in the post-transplant period. To detect the loss of HLA heterozygosity, the method using the commercial KMR-HLA system and analysis using next-generation sequencing (NGS), as well as the method based on the analysis of highly polymorphic STR and VNTR markers located in the HLA loci region on the short arm of chromosome 6, are widely used. The primary objective of our study was to compare the informativeness of these approaches in diagnosing HLA heterozygosity loss in children during the post-transplant period. The obtained data on the frequency of detecting HLA heterozygosity loss were comparable to the literature data and constituted 23 % of cases of post-transplant relapse of B-cell acute lymphoblastic leukemia, 33 % of cases of T-cell acute lymphoblastic leukemia, and 23% of cases of acute myeloid leukemia. We also demonstrated that the method based on STR marker analysis has sensitivity comparable to allele-specific PCR and NGS sequencing methods. Meanwhile, preliminary sorting of the blast population increases the sensitivity of STR analysis and can be recommended in routine practice.

Introduction. We report preliminary results of a pilot clinical trial of therapeutic DNA vaccination of patients with neuroblastoma (NCT04049864).

The aim of the study – is to test the safety and immunogenicity of DNA vaccination against neuroblastoma.

Materials and methods. The results of 6 patients who completed vaccination are summarized in the article. Inclusion and exclusion criteria for patients are defined. The clinical protocol included vaccine form and doses, timed vaccination regimen, and concomitant therapy. Minimal residual disease was analyzed for all patients by quantitative polymerase chain reaction, measurement of T-cell immune response by ELISpot and antisense response by ELISA.

Results. The vaccine was well tolerated by patients with minimal adverse symptoms. T-cell immune response was evaluated two weeks after each course of vaccination and was positive in 5 of 6 patients. An antisense immune response was detected in 1 patient. 5 out of 6 patients are alive and in clinical remission as of 11/01/2022. Event-free survival of vaccinated patients was 82 ± 18 % vs 29 ± 11 % of controls (p = 0.03).

Introduction. Fibroadenomas are the most common benign tumors of the mammary glands in children and adolescents. In some cases, they may be part of hereditary tumor predisposition syndromes associated with a high risk of developing malignant neoplasms throughout life, and therefore genetic testing is relevant.

The purpose of the study is to discribe the spectrum of genetic mutations in cancer-associated genes according to the results of next generation sequencing (NGS) in young patients with breast fibroadenomas.

Matherials and methods. Sixteen teenage girls with fibroadenomas of the breast who were followed up in Research Institute of Pediatric Oncology and Hematology from 2020 to 2023 were enrolled in this study. Genetic testing by NGS was performed.

Results. Pathogenic variants in cancer-associated genes were found in 4 (25 %) patients. In two cases, fibroadenomas were a part of Cowden’s syndrome associated with PTEN inactivation; two patients carried pathogenic variants in the BRCA1 and BRCA2 genes.

Conclusion. Genetic testing of young patients with breast fibroadenomas is important to optimize the management strategy in order to reduce cancer risk in high-risk groups of patients.

Thyroid diseases in childhood occupy the second place after obesity in the structure of the general pathology of the endocrine system, eating disorders and metabolic disorders in children in the Russian Federation. Thyroid cancer in children makes up from 1.5 to 3 % of all malignant tumors, and from 8 to 22 % of malignant solid tumors of the head and neck, and the younger the child’s age, the more aggressive the disease proceeds.

Familial forms of thyroid diseases may be associated with geographical features (living in iodine-deficient regions), but may also be part of hereditary syndromes, such as: multiple endocrine neoplasia syndromes (Sipple syndrome, Gorner syndrome, familial medullary thyroid cancer), DICER1 syndrome, Gardner syndrome, Cowden syndrome, McCune–Albright–Braitsev syndrome et al.

This article describes several cases of thyroid pathology associated with DICER1 syndrome.

Pancreatoduodenal resection (PDR) is one of the most difficult surgical interventions in abdominal surgery of childhood. We present our clinical observation of a postoperative complication in a 14-years-old girl.

The girl was operated on for a solid pseudopapillary tumor of the head of the pancreas, laparoscopically assisted pylori-preserving PDR was performed, mobilization and removal of the tumor was performed, distally between the stump of the pancreas and the Roux-en-Y loop of pancreatoejunoanastomo was formed. Mechanical jaundice occurred in the late postoperative period. Percutaneous transhepatic cholangiostomy, recanalization of hepaticoejunoanastomosis with the formation of external-internal transhepatic drainage was performed. 5 courses of balloon dilation of the stricture of the biliodigestive anastomosis were performed later.

We demonstrate some complications of PDR in children and show possible options for their correction.