Clinical features of the disease course in patients with solitary plasmacytoma and extramedullary multiple myeloma

Objective: to study the clinical laboratory features of the course of solitary plasmacytoma (SP) and extramedullary multiple myeloma (EMM). Material and methods. The study included 42 people (22 patients newly diagnosed with EMM and 20 patients diagnosed with SP of various localization). The results were evaluated after 3 years of the study. The median age in the SP group was 61.5 years, in the EMM group — 65 years. Results. A comparative analysis of the SP and EMM groups in terms of the clinical and laboratory parameters has found no statistical differences in the distribution of immunochemical variants. Significant differences were found in the frequency of determination of the abnormal ratio of immunoglobulin light chains (p = 0.046). In EMM, extramedullary lesions were the most common for patients with multiple lytic bone lesions of the skeleton. SP was the most frequently detected in lesions of the peripheral skeletal bones and vertebral bodies. Clinically, EMM was characterized by a more aggressive course if additional factors of an unfavorable prognosis (translocations, mutations) or unfavorable immunophenotypic markers (a combination of signs — expression of markers CD56 > 20 % and CD95 < 20 %) were identified or if the disease had been diagnosed at a young age. The presence of even a minimal number of tumor or aberrant plasma cells in the bone marrow of SP patients, an abnormal ratio of immunoglobulin light chains, paraprotein detected in blood serum or urine were all poor prognostic factors. Conclusion. The clinical course of SP and EMM combined with a young age, the presence of translocations or mutations, unfavorable immunophenotypic markers, is characterized by an increased frequency of progression or the development of resistance to the performed therapy.