A new phenotypic classification of bone marrow plasmacytosis

Area of Science:

• Hematology
• Immunology
• Oncology

Background:

• Bone marrow plasmacytosis requires accurate classification for diagnosis and prognosis.
• Current methods may not fully differentiate reactive from neoplastic plasma cells or their maturation stages.

Purpose of the Study:

• To introduce a novel phenotypic classification for bone marrow plasmacytosis.
• To differentiate between polyclonal (reactive) and monoclonal (neoplastic) plasma cells.
• To subclassify monoclonal marrow plasmacytosis (MOMP) based on plasma cell maturity for prognostic insights.

Main Methods:

• Utilized 2-color flow cytometry with FITC anti-CD38 and PE-conjugated antibodies (anti-CD19, -CD56, -VLA-5, MPC-1).
• Phenotypically classified plasma cells into polyclonal (CD19+CD56-) and monoclonal (CD19-CD56+).
• Further categorized plasma cells by maturity: immature (VLA-5-MPC-1-), intermediate (VLA-5-MPC-1+), and mature (VLA-5+MPC-1+).

Main Results:

• Established a classification system: polyclonal marrow plasmacytosis (POMP) and monoclonal marrow plasmacytosis (MOMP).
• MOMP was subclassified into MOMP-1 (co-existing monoclonal and polyclonal cells, associated with benign monoclonal gammopathy) and MOMP-2 to MOMP-4 (increasing immature myeloma cells, associated with myeloma).
• Increased immature myeloma cells (MOMP-2 to MOMP-4) correlated with disease aggravation.

Conclusions:

• The proposed phenotypic classification (POMP and MOMP-1 to MOMP-4) offers improved differential diagnosis for bone marrow plasmacytosis.
• This classification aids in understanding therapeutic responses and predicting prognosis in myeloma patients.
• Subclassification of MOMP, particularly the proportion of immature myeloma cells, is valuable for clinical management.