Digital image analysis of mean AgNOR area objectively discriminates between reactive plasmacytosis and multiple myeloma in cytologic smears from bone marrow aspirates.

OBJECTIVE To differentiate between reactive plasmacytosis (RP) and multiple myeloma (MM) in bone marrow aspirates by assessment of silver-stainable nucleolar organizer regions (AgNORs). METHODS Archival cytologic smears (n = 69) from bone marrow aspirates were retrospectively investigated. Twenty cases had RP and 49 cases MM (24 low-grade, 22 intermediate-grade and 3 high-grade MM). Diagnoses were confirmed by evaluation of the corresponding bone marrow trephine biopsies. Cytologic smears were subjected to AgNOR staining using a standardized silver-staining protocol and assessed by two independent clinical histopathologists using digital image analysis. AgNOR count and area were analyzed in 100 plasma cell nuclei per sample. RESULTS The mean AgNOR area was found to be significantly (p < 0.001) higher in low-grade MM (mean: 23.4 microm(2); range: 19.2-26.7 microm(2)) than in RP cases (mean: 6.2 microm(2); range: 3.8-8.4 microm(2)). In contrast, mean AgNOR count failed to disclose significant differences between low-grade MM (mean: 5.36; range: 1-7) and RP (mean: 3.68; range: 1-6). CONCLUSION Digital image analysis of the mean AgNOR area might be used as a diagnostically useful adjunct to aid objectively in the challenging differentiation between RP and MM in bone marrow aspirates.