Extramedullary disease of multiple myeloma (EM) remains a treatment challenge even in the era of new drugs. While many reports analyzing various aspects of EM have been published, mechanism of EM development has not been clarified yet. This review summarizes current knowledge about this clinical entity, including its history, diagnostics, imaging methods, incidence, prognosis, current treatment options, risk factors and known molecular mechanisms that might be involved in pathogenesis of EM.

Objectives: Progress in multiple myeloma treatment allows patients to achieve deeper responses, for which the assessment of minimal residual disease (MRD) is critical. Typically, bone marrow samples are used for this purpose; however, this approach is site‐limited. Liquid biopsy represents a minimally invasive and more comprehensive technique that is not site‐limited, but equally challenging.Methods: While majority of current data comes from short‐term studies, we present a long‐term study on blood‐based MRD monitoring using tumor‐specific cell‐free DNA detection by ASO‐qPCR. One hundred and twelve patients were enrolled into the study, but long‐term sampling and analysis were feasible only in 45 patients.Results: We found a significant correlation of quantity of tumor‐specific cell‐free DNA levels with clinically meaningful events [induction therapy (P = .004); ASCT (P = .012)]. Moreover, length of cfDNA fragments is associated with better treatment response of patients.Conclusions: These results support the concept of tumor‐specific cell‐free DNA as a prognostic marker.

Summary: Plasma cell leukaemia (PCL) is a rare and very aggressive plasma cell disorder. Preventing a dismal outcome of PCL requires early diagnosis with appropriate analytical tools. Therefore, the investigation of 33 patients with primary and secondary PCL was done when the quantity of circulating plasma cells (PCs) using flow cytometry (FC) and morphology assessment was evaluated. The phenotypic profile of the PCs was also analysed to determine if there is an association with clinical outcomes and to evaluate the prognostic value of analysed markers. Our results revealed that FC is an excellent method for identifying circulating PCs as a significantly higher number was identified by FC than by morphology (26·7% vs. 13·5%,P = 0·02). None of secondary PCL cases expressed CD19 or CD20. A low level of expression with similar positivity of CD27, CD28, CD81 and CD117 was found in both PCL groups. A decrease of CD44 expression was detected only in secondary PCL. Expression of CD56 was present in more than half of PCL cases as well as cytoplasmic nestin. A decreased level of platelets, Eastern Cooperative Oncology Group score of 2–3 and lack of CD20⁺PC were associated with a higher risk of death. FC could be incorporated in PCL diagnostics not only to determine the number of circulating PCs, but also to assess their phenotype profile and this information should be useful in patients’ diagnosis and possible prognosis.

Teclistamab, a BCMA×CD3 bispecific antibody, demonstrates high efficacy in relapsed/refractory multiple myeloma (RRMM). However, optimal dosing strategies outside clinical trials remain undefined. Thus, we performed a retrospective, multicentre analysis of 73 RRMM patients treated with teclistamab monotherapy at Czech Myeloma Group centres between 2023 and 2025. The study compared efficacy and safety between patients receiving standard weekly dosing and those with reduced-frequency dosing. The whole cohort had a median age of 67 years; 68.5% were penta-refractory. Dosing was de-escalated in 24.7% of patients, typically within one month of treatment initiation. Median progression-free survival (PFS) was 9.41 months and was comparable between weekly and non-weekly groups (9.1 vs. 11.3 months; p = 0.141), despite a significantly lower relative dose intensity in the latter (60.5% vs. 87.0%; p < 0.001). Infection rates and severe adverse events were similar between groups. A lower incidence of neutropenia was observed with less frequent dosing, but this did not translate into reduced infection burden. In conclusion, in real-world practice, early de-escalation of teclistamab dosing appears to maintain clinical efficacy. These findings support ongoing efforts to individualize treatment schedules with the aim of balancing effectiveness, tolerability, and patient-specific factors in BCMA-targeted therapy.

Diagnostic relevance of 18F-FDG PET/CT in newly diagnosed patients with monoclonal gammopathy of undetermined significance (MGUS): Single-center experience