21.4. Multiple solitary plasmacytoma

Chapter 21

Up to 5% of patients presenting with solitary plasmacytomas go on to develop multiple lesions in the bone or elsewhere, without evidence of MM [470]. The criteria for diagnosing patients with multiple solitary plasmacytomas are shown below. As with solitary plasmacytoma, sFLC measurements may be helpful in managing these patients.

Criteria for the diagnosis of multiple solitary plasmacytomas (± recurrent) [470]

▪ Low concentration or absence of monoclonal protein in serum and/or urine

▪ More than one localised area of bone destruction or extramedullary tumour of clonal plasma cells, which may be recurrent

▪ Normal bone marrow

▪ Normal skeletal survey and MRI of spine and pelvis if done

▪ No related organ or tissue impairment (no end organ damage other than the localised bone lesions)


  1. What is the reported 5-year risk of progression to MM in SPB patients with an abnormal κ/λ sFLC ratio?
  2. Based on the risk stratification model reported by Dingli et al. [472], which two factors can effectively discriminate SPB patients at low, medium and high risk of progression to MM?
  3. Which two risk factors were defined by Fouquet et al. [476] to identify solitary plasmacytoma patients at risk of progression to MM?


  1. 44% (Section 21.2.2).
  2. The κ/λ sFLC ratio at baseline and the persistence of a monoclonal immunoglobulin after 1 - 2 years (Section 21.2.2).
  3. An abnormal involved sFLC concentration and the presence of ≥2 lesions by PET CT at baseline (Section 21.2.2).