Fig 1.

Temporal evolution of myeloma clones. As myeloma progresses, clones can theoretically undergo three different changes. (A) Progression of myeloma can occur as a result of the expansion of clonal size while the diversity of the clones remains the same. (B) Progression of myeloma may be a result of the increase of clonal diversity as additional clones emerge over time, while the size of each clone remains stable. (C) Myeloma clones can increase both in size and diversity at the same time, which potentially projects to a greater tumor burden (greater height). Studies have suggested that the diversification of clonal heterogeneity may occur as an early event as in (B) and (C), whereas the expansion of the size of each clone follows later within the existing library of clones as in (A).^7,15