Background. Multiple myeloma complicated by extramedullary plasmacytoma is an unfavorable variant of the disease. It remains unknown what triggers tumor transformation. The review presents literature data on the pathogenesis of extramedullary disease, as well as a clinical example of a comprehensive study of the tumor substrate.Aim. To study the molecular and biological characteristics of the tumor substrate of the bone marrow and extramedullary plasmacytoma using various research methods.Materials and methods. A 55-year-old patient was admitted to National Medical Research Center for Hematology with a diagnosis of multiple myeloma occurring with extramedullary plasmacytoma of the retroperitoneal space. dNA was isolated from samples of different localization (blood plasma, Cd138+ bone marrow cells, plasmacytoma and buccal epithelial cells). The profile of short tandem dNA repeats (STR) from the obtained samples was studied by multiplex polymerase chain reaction followed by fragment analysis. fluorescent in situ hybridization (fISH) of bone marrow Cd138+ cells was performed using various dNA probes. Comparative genomic hybridization on a microarray (arrayCGH) plasmacytoma dNA was also performed. The mutation profile of the KRAS, NRAS, BRAF genes was studied by Sanger sequencing in tumor samples of various localizations.Results. The induction therapy (vCd (bortezomib + cyclophosphamide + dexamethasone), vRd (bortezomib + lenalidomide + dexamethasone), daratumumab therapy) was ineffective, death occurred 4 months after the first clinical manifestations appeared. Comparison of STR markers of circulating cell-free tumor dNA (cfdNA), Cd138+ bone marrow cells, and plasmacytoma revealed the largest number of involved loci exactly in plasmacytoma’ dNA. A mutation in the NRAS gene was found only in plasmacytoma’ dNA. This indicates the presence of another clone of tumor cells in the extra-medullary plasmacytoma. Molecular karyotyping of plasmacytoma using the arrayCGH method revealed rearrangements of many chromosomes. 1p32.3 bi-allelic deletion, amplification of 1q21, 8q24/MyC rearrangements and del17p13 were confirmed by arrayCGH molecular karyotyping and fISH studies in bone marrow and plasmacytoma.Conclusion. A comprehensive molecular genetic study of the extramedullary plasmacytoma’ substrate is necessary to understand the pathogenesis mechanisms and, on this basis, to develop differentiated therapeutic approaches.

Multiple myeloma (MM) is a disease characterized by spatiotemporal heterogeneity of tumor clones. Different genetic aberrations can be observed simultaneously in tumor cells from different loci, and as the disease progresses, new subclones may appear. The role of liquid biopsy, which is based on the analysis of tumor DNA circulating in the blood plasma, continues to be explored in MM. Here, we present an analysis of the STR profiles and mutation status of the KRAS, NRAS, and BRAF genes, evaluated in plasma free circulating tumor DNA (ctDNA), CD138+ bone marrow cells, and plasmacytomas. The prospective single-center study included 97 patients, with a median age of 55 years. Of these, 94 had newly diagnosed symptomatic MM, and three had primary plasma cell leukemia. It should be noted that if mutations were detected only in ctDNA, “non-classical” codons were more often affected. A variety of adverse laboratory and clinical factors have been associated with the detection of rare KRAS or NRAS gene mutations in bone marrow or ctDNA, suggesting that these mutations may be factors of an unfavorable prognosis for MM. Liquid biopsy studies provide undeniable fundamental information about tumor heterogeneity and clonal evolution in MM. Moreover, we focus on using liquid biopsy to identify new high-risk factors for MM.

Multiple myeloma (MM) is characterized by heterogeneity of tumor cells. The study of tumor cells from blood, bone marrow, plasmacytoma, etc., allows us to identify similarities and differences in tumor lesions of various anatomical localizations. The aim of this study was to compare the loss of heterozygosity (LOH) by tumor cells by assessing STR profiles of different MM lesions. We examined paired samples of plasma circulating tumor DNA (ctDNA) and CD138+ bone marrow cells in MM patients. For patients with plasmacytomas (66% of 38 patients included), the STR profile of plasmacytomas was also studied when biopsy samples were available. Diverse patterns of LOH were found in lesions of different localization for most patients. LOH in plasma ctDNA, bone marrow, and plasmacytoma samples was found for 55%, 71%, and 100% of patients, respectively. One could expect a greater variety of STR profiles in aberrant loci for patients with plasmacytomas. This hypothesis was not confirmed—no difference in the frequency of LOH in MM patients with or without plasmacytomas was found. This indicates the genetic diversity of tumor clones in MM, regardless of the presence of extramedullar lesions. Therefore, we conclude that risk stratification based on molecular tests performed solely on bone marrow samples may not be sufficient for all MM patients, including those without plasmacytomas. Due to genetic heterogeneity of MM tumor cells from various lesions, the high diagnostic value of liquid biopsy approaches becomes obvious.

DNA samples from patients with hairy cell leukemia (HCL) and splenic marginal zone B-cell lymphoma (MZBCL) for BRAF and MAP2K1 activating mutations were analyzed. V600E mutation of BRAF was detected in 39 (98 %) of 40 patients with hairy cell leukemia, and no patient with MZBCL. In none of the patients in this study any other activating mutations than V600E in exons 11 and 15 of BRAF gene were revealed. MAP2K1 Q56P mutation characterized by IGHV4-34 expression was detected in 1 (2 %) of 40 patients with HCL. In none of the patients with MZBCL activating mutations in the 2, 3 or 11 exons of MAR2K1 gene have been identified, including those with IGHV4-34 expression.

Multiple myeloma (MM) is a complex genetic disease characterized by the heterogeneity of tumor cells. We have measured KRAS, NRAS, and BRAF gene mutations in circulating free tumor DNA (ctDNA) from plasma, bone marrow, and plasmacytoma samples as well as their correlation with various clinical and laboratory parameters. The prospective study included 113 MM patients (74 with plasmacytoma and 39 without), treated at the National Medical Research Center for Hematology (Moscow, Russia) from 2009 to 2024. FISH was performed on CD138+ bone marrow cells for 104 patients and array-CGH for two extramedullary plasmacytoma samples. Mutation analysis on CD138+ bone marrow cells was performed for 99 patients, on ctDNA for 80 patients, and, in 26 cases, samples of plasmacytoma were also investigated. Mutations in the KRAS, NRAS, and BRAF genes either in bone marrow, ctDNA, or plasmacytoma samples were found in 50% of patients. In patients with plasmacytoma, mutations in ctDNA were found in 28% of cases versus 0% in cases without plasmacytoma (p = 0.0007). Rare “noncanonical” KRAS and NRAS gene mutations were also more frequent in ctDNA compared to the bone marrow substrate (50% versus 9%, p = 0.01). Liquid biopsy in MM, particularly identification of the KRAS, NRAS, and BRAF gene mutations in ctDNA, is a valuable instrument for prognostication. Researching the intricate mechanisms underlying extramedullary involvement, and identifying novel high-risk factors associated with the disease, is worthwhile.

Background. Multiple myeloma (MM) is a genetically complex disease in which different aberrations can be determined in tumors of different localizations. The impact of mutations in the RAS-ERK pathway genes on the MM course, despite numerous publications, is unclear. Aim. To evaluate mutations in the KRAS, NRAS, BRAF genes in plasma free circulating tumor DNA and CD138+ bone marrow cells and to analyze therapy results of MM patients at different stages depending on MAP kinase genes mutational status. Materials and methods. A prospective single-center study from September 2021 to December 2024 included 100 patients (45 men and 55 women) with newly diagnosed MM aged 29 to 83 years (median 55 years), 41 patients without plasmacytomas and 59 with plasmacytomas. The diagnosis was established in accordance with International Myeloma Working Group – 2014 criteria. Induction therapy was performed according to bortezomib-containing programs; the antitumor response was assessed according to International Myeloma Working Group – 2016 criteria. Analysis of KRAS, NRAS, BRAF genes mutations on DNA samples of CD138+ bone marrow cells was performed in all patients, in free circulating tumor DNA – in 81 patients. Statistical analysis was performed using the MedCalc program, and the Fisher criterion was also used. Survival analysis was performed using the Kaplan–Meier method, with statistical significance assessed using the log-rank test. Results. The frequency of KRAS, NRAS, BRAF genes mutations in free circulating tumor DNA and / or bone marrow in the total group was 50 %. The detection frequency of MAP kinase genes mutations in patients with and without plasmacytomas was comparable. No differences in detection frequency of high-risk cytogenetic aberrations were found in groups of patients with RAS-ERK pathway genes mutations and without them. A tendency towards a lower frequency of achieving complete remission after induction therapy was noted in patients with mutated gene status compared to patients without MAP kinase genes mutations (17 % versus 41 %; p = 0.07). At control time points after auto-transplantation, the trend remained: patients with MAP kinase genes mutations achieved a deep antitumor response 2 times less often compared to patients without mutations (30 % versus 59.5 %; p = 0.051). The probability of two-year progression-free survival of patients with MAP kinase genes mutations was significantly lower (p 0.05) – 62 % versus 92 % for patients without KRAS, NRAS, BRAF genes mutations. Conclusion. Due to the complex genetic structure and spatial anatomical heterogeneity of MM, the study of various localization tumors is extremely relevant. When mutations in the MAP kinase genes are detected, the antitumor response at various therapy stages is worse, and the probability of progression-free survival is significantly lower than in patients without mutations in these genes.