APM component expression in premalignant plasma cells from BM of MGUS patients with different disease progression in the 24 months after BM sampling. MGUS patients who progressed to MM (○, n = 6) and who did not progress (◇, n = 14) are shown. Immunostaining and flow cytometric analysis were performed to obtain percentages of positive cells (A) and MESF (B), as described in Figure 2. *P < .05, **P ≤ .005, Mann-Whitney test.