Correlation between malignant plasma cells detected in bone marrow by flow cytometry and clinicopathological features of multiple myeloma patients and its impact on prognosis

Background Multiple myeloma (MM) is a plasma cell disorder characterized by abnormal proliferation of monoclonal plasma cells. While multiparametric flow cytometry has advanced MM diagnosis and risk assessment, the quantification of plasma cells in newly diagnosed patients remains underexplored. This study aimed to evaluate malignant plasma cells in the bone marrow (BM) of newly diagnosed MM patients using multiparametric flow cytometry and to examine their association with clinicopathological features and disease outcomes. Patients and methods This prospective study included 30 newly diagnosed MM patients aged 45–70 years and assessed BM malignant plasma cells by flow cytometry, alongside standard clinical and laboratory evaluations. Results Our results showed that patients with poor treatment response had significantly higher levels of malignant plasma cells (mean 88.55%) than those with good response (mean 57.29%; P <0.001). Total BM plasma cell percentages were also elevated in poor responders (57.0 vs. 35.38%, P =0.001). Receiver operating characteristic (curve) analysis demonstrated that the percentage of malignant plasma cells was a strong prognostic marker, with an area under the curve of 0.923 (95% Confidence Interval: 0.832–1.0, P <0.001). A cut-off of less than or equal to 80.3% provided 92.31% sensitivity and 76.47% specificity, underscoring its prognostic value. Conclusion Malignant plasma cell quantification by flow cytometry is a highly sensitive and specific tool for early prognostic stratification in MM patients, and its integration into routine diagnostic panels is recommended to enhance treatment planning and patient outcomes.