Enumeration of plasma cells in the bone marrow of persons with multiple myeloma: Correlation between conventional panoptical microscopy of the aspirate, flow cytometry and bone marrow biopsy.

Abstract Background: The diagnosis of multiple myeloma (MM) needs the enumeration of the plasma cells (PC) in the bone marrow (BM); the percentage of PC is critical to establish the diagnosis and it can be accomplished by conventional panoptical microscopy (CPM) of the BM aspirate, flow cytometry (FC) or BM biopsy (BMB). Objective: To analyze the correlation of the three methods employed to enumerate PC in the BM of persons with MM, at diagnosis. Methods: Enumeration of the PC in the BM of 73 persons with MM was done by means of CPM, FC and/or BMB, at diagnosis. Results: 73 patients were analyzed. CPM was employed in all cases, FC in 69 and BMB in 37, at diagnosis. The number of PC had a median of 29.9% (IQR = 4.96 - 68.4), 6% (IQR = 6 - 17.1) and 10% (IQR = 5 - 40) employing CPM, FC, and BMB respectively. Enumeration of BM PC was higher employing CPM. The correlation coefficients were 0.5215 (between CPM and FC), 0.6346 (between CPM and BMB), and 0.2179 (between BMB and FC). A correlation between overall survival (OS) and BM PC employing CPM, FC and BMB was analyzed finding no statistically significant difference between the method used to diagnose MM and patients' OS (p = 0.7946). Conclusion: In persons with MM, BM PC can be enumerated by CPM, FC and BMB. The differences in the figures obtained should be considered when defining the diagnosis of MM. There was no statistically significant correlation between the OS of MM patients and the number of PC in the BM at diagnosis, regardless of the method used to identify PC (BMB, FC or CPM).