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Background. A significant advancement in the treatment of high-grade aggressive non-Hodgkin’s lymphomas and acute lymphoblastic leukemia is the inclusion of high-dose (1000–5000 mg/m2) methotrexate in the treatment protocol. This approach has significantly increased the long-term survival rate, but it has been associated with toxicity, requiring supportive care. Factors that predict toxicity were identified, including genes involved in the metabolism (MTHFR) or transport (SLCO1B1) of methotrexate. The analysis of methotrexate metabolism has identified additional genes responsible for the elimination of this drug, allowing for more effective prevention and treatment of methotrexate-associated toxicity.Aim. To study the genetic polymorphisms of enzymes involved in the methotrexate metabolism and associated toxicity in the treatment of pediatric acute lymphoblastic leukemia and non-Hodgkin’s lymphomas.Materials and methods. Data were analyzed in specialized medical databases such as Pubmed, Scopus, Web of Science, Frontiers, and Google Scholar from 2001 to 2024.Results. The main predictors of high-dose methotrexate-associated toxicity are gene polymorphisms in MTHFR, SLCO1B1, ARID5B.Conclusion. Despite the contradictory data presented in the literature, it is important to consider the detection of polymorphisms during high-dose methotrexate treatment in order to administer timely supportive care and prevent significant toxicity.

Histiocytic cell tumors present as a difficult group of diseases in terms of differential diagnosis due to their rare frequency, heterogeneous clinical manifestations and ambiguous clinical course. Considering MAPK-signaling pathway mutations role (including BRAFV600E) in the pathogenesis of histiocytic cell tumors the importance of genetic studies in the diagnosis and choice of therapeutic strategy in these diseases increases. In the current issue modern classifications of histiocytic cell tumors, morphological and immunophenotypic features of histiocytic and dendritic cells, and the role of recurrent somatic mutations of the MAPK signaling pathway in the pathological histiocytic proliferation are presented. Particular attention is given to Langerhans cell histiocytosis, Erdheim–Chester disease and juvenile xanthogranuloma. Clinical and diagnostic characteristics of these diseases and therapeutic approaches are presented.

Histiocytic tumors are a highly heterogeneous group of diseases, with Langerhans cell histiocytosis occupying the main place among it. Despite the rare frequency of occurrence, long-term analysis of clinical, morpho-immunological and molecular-biological features has allowed the development of effective treatment protocols (especially in the pediatric cohort of patients). In addition to Langerhans cell histiocytosis, the histiocytic tumors group includes rare and casuistic variants, which include histiocytic sarcoma, Langerhans cell sarcoma, indeterminate dendritic cell tumor, interdigitating dendritic cell sarcoma, follicular dendritic cell sarcoma, and fibroblastic reticular cell tumor. The incidence of certain nosological variants is several cases per hundreds of millions of the population. Not surprisingly, the diagnostic criteria for this group of tumors need to be clarified, as do the therapeutic approaches. This review presents current data on rare histiocytic tumors, clinical features as well as morphological and immunobiological characteristics of the tumor substrate. The results of modern surgical and therapeutic treatment approaches are presented.