Risk of SMM progression to active MM according to different prognostic systems as compared with risk of progression of MGUS to active MM. Gray shading includes 2-year time point. (A) SMM risk based on BMPCs ≥ 10%, M protein ≥ 30 g/L.²¹  Bold solid line, both above threshold; solid line, BMPCs ≥ 10% but M-protein < 30 g/L; dashed line, BMPC < 10% but M-protein ≥ 30 g/L. (B) SMM risk based on BMPC ≥ 10, M protein ≥ 30 g/L, and involved FLC/uninvolved FLC ≥ 8.²⁵  Bold solid line, all 3 factors above threshold; solid line, any 2 factors above threshold; dashed line, any 1 factor above threshold. (C) SMM risk based on involved FLC/uninvolved FLC ≥ 100.²⁶  Bold solid line, above threshold; solid line, below threshold. (D) SMM risk based on absence of CD19 and/or CD45 expression, overexpression of CD56, or weak expression of CD38 and immunoparesis of either of the uninvolved immunoglobulins.³¹  Bold solid line, both risk factors present; solid line, either risk factor present; dashed line, neither risk factor present. (E) SMM risk based on presence (bold solid) or absence (solid) of more than 1 focal lesion on whole-body MRI.³⁴  (F) SMM risk based on FISH.³⁸  Bold solid line, del17p,or t(4;14); solid line, trisomies alone; dashed line, any other interphase FISH abnormality; dotted line, normal or insufficient interphase FISH. (G) SMM risk based on high-risk interphase FISH [del17p, t(4;14), +1q21, or hyperdiploidy] and high tumor burden (M-protein ≥ 20 g/L).³⁹  Bold solid line, both high-risk factors present; solid line, interphase FISH low risk and tumor high risk; dashed line, FISH high risk and tumor low risk; dotted line, both low risk. (H) MGUS risk of progression to MM based on M protein ≥ 30 g/L, abnormal rFLC, and heavy chain IgA or IgM.⁶⁰  Bold solid line, all risk factors present; solid line, 2 risk factors present; dashed line, 1 risk factor present; dotted line, no risk factor present.