Background. Classical Hodgkin’s lymphoma is a B-cell lymphoproliferative disease, the tumor substrate of which is Berezovsky–Reed–Sternberg cells, characterized by CD30, PAX-5, CD15 expression and the absence of CD3, CD45. In some cases, tumor cells express CD20. modern anticancer therapy has increased the survival probability for most patients, not only with early but also with advanced stages of classical Hodgkin’s lymphoma. Such successes are mainly due to the distribution of patients into prognostic groups and the choice of an appropriate treatment regimen. tumor infiltration of the bone marrow suggests assigning patients to the advanced stages group, followed by the choice of an intensive therapy program. Aim. To determine the bone marrow involvement frequency according to positron emission tomography combined with computed tomography (PET/CT), with 18F-fluorodeoxyglucose (FDG) and bone marrow trephine biopsy (bmtb), to compare the results obtained with primary tumor immunophenotype and bone marrow cellular composition, and to identify of prognostic risk factors. Materials and methods. The study included 107 patients with newly diagnosed classical Hodgkin’s lymphoma, who underwent a diagnostic examination at the moscow research institute of oncology named after P. A. Herzen – a branch of the National Medical Research Center for Radiology and the “Lapino” clinical Hospital from 2015 to 2022, followed by anticancer therapy and further follow-up. Morphology of the primary tumor biopsy specimen in all patients and immunohistochemical (IHC) study using a wide panel of monoclonal antibodies (CD15, CD30, CD3, CD45, CD20, PAX-5 anti-gens; in some cases epstein–barr virus proteins expression) in most cases were performed. All patients underwent a morphological and / or IHC study of BMTB and the majority underwent aspiration biopsy and PET/CT with 18F-FDG. Results. The most common histological variant of classical Hodgkin’s lymphoma was nodular sclerosis (86.9 %). The majority of patients (51.4 %) were assigned to the advanced stage prognostic group. bone marrow tumor infiltration was statistically significantly more frequently diagnosed during PET/CT with 18F-FDG compared with the results of the BMTB – in 27.1 % and 12.1 % of cases, respectively (p < 0.05). when comparing the results of both diagnostic methods, it was found that in 17.1 % of cases, bone marrow infiltration, detected during PET/CT, was not confirmed by IHC examination of the trephine biopsy. In addition, it was found that the majority of cases with CD20+/± and CD15+/± expression in the primary tumor were observed in the group of patients without bone marrow involvement. when assessing the cellular composition of bone marrow aspirates, it was revealed that in patients with bone marrow tumor infiltration, an increase in cellularity and megakaryocytes number along with a decrease in the plasma cells number is observed. Conclusion. The results suggest further study of bone marrow immunomorphological features in order to identify prognostic factors and search for new therapeutic targets. a more extended analysis of bone marrow aspirate immunomor-phological characteristics using new modern diagnostic methods, minimal residual disease status as a surrogate marker seems to be relevant and necessary to confirm the depth of the antitumor response achieved. Detection of CD20+/±- and cd15+/±-Berezovsky–Reed–Sternberg cells according to primary tumor IHC analysis indicates a low probability of bone marrow tumor infiltration, but further analysis is required on a large clinical and laboratory material.
