[Prognostic significance of morphology in multiple myeloma]

Multiple myeloma is the second most common hematological disease caused by clonal proliferation of B cells. Evaluation of number of plasmocytes in the bone marrow is still one of the basic diagnostic criteria. The aim of this study was to verify if this evaluation has prognostic value even in the era of new drugs.

Two groups of MM patients were enrolled in this study. The group T - 45 newly diagnosed MM patients who underwent treatment with thalidomide. Group B - 86 patients in first relapse of MM without autologous transplantation of bone marrow that were treated with thalidomide and bortezomib in various combinations. Percentage of subtypes of plasmocytes in the bone marrow was evaluated based on progressive analysis of nucleus, chromatin and nucleo-cellular ratio (N/C).

Mature plasma cells were found in 53.3% (group T) and 53.5% (group B) of patients; proplasmocytes I were found in 22.2% (group T) and 24.4% (group B) of patients; proplasmocytes II were found in 22.2% (group T) and 22.1% (group B) of patients and plasmablasts in 1% (group T) and 0% (group B). Patients who reached treatment response after first treatment had statistically significant number of proplasmocytes II when compared to group without treatment response (median 37% vs. 11%, p = 0.033). Group B patients with mature plasmocytes below 10% had significantly shorter overall survival than other patients when comparison of quartiles was performed. Group B patients with higher infiltration of proplasmocytes I than median of 15% had lower overall survival (median 50.3 months vs. 74.9 months, p = 0,024); the same was true for evaluation of proplasmocytes II (median OS 41.3 months vs. 74.9 months, p = 0,011).

Numerical evaluations of plasma cells in the bone marrow remain basic diagnostic criteria of MM even in the era of new genomics analyses. More precise morphological evaluation of 8 subtypes of plasma cells brings important prognostic information that is necessary for new protocols for immunomodulatory drugs and proteasome inhibitors.