Review of phenotypic markers used in flow cytometric analysis of MGUS and MM, and applicability of flow cytometry in other plasma cell disorders.

Flow cytometric immunophenotyping is considered an indispensable tool for the diagnosis, classification and monitoring of disease in monoclonal gammopathies. The clinical sensitivity of flow cytometry is comparable with advanced molecular methods. Clinical application of flow cytometry in monoclonal gammopathies has various dimensions, such as differential diagnosis of malignant plasma cell disorder from reactive plasmacytosis, identifying the progression risk in monoclonal gammopathy of undetermined significance (MGUS) and asymptomatic multiple myeloma (MM), and minimal residual disease detection. Flow cytometry-based clonality assessment with immunophenotyping encourages and enables the most stringent method of diagnosis and follow-up. The objective of this review is to update the malignant plasma cells phenotypic profile of MGUS and MM. The most comprehensive antigens, such as CD19, CD27, CD28, CD45, CD56 and CD117, play a significant role in the characterization of normal and malignant plasma cells. Several research groups described the putative phenotype of myeloma cell progenitors, but no remarkable suggestion could be made because of disparity. This review also focuses on the association of malignant phenotypic markers and chromosomal aberrations that identify the specific prognostic features in monoclonal gammopathies.