NK cell features during the early phases of disease: from MGUS to MM. (A) Comparative analysis of frequency of total NK cells (top), frequency of CD94^lowCD56^dim NK cells (middle), and frequency of Ki67⁺ NK cells (bottom) in PB and BM of MGUS, sMM, and MM patients compared with HDs. (B) NK cell analysis in a representative patient evolving from MGUS to sMM and eventually to MM. Dot plots depict frequency of CD94^lowCD56^dim NK cells and Ki67 analyzed on NK cells from both PB and BM of the patient along disease progression.