Solitary extramedullary plasmacytomas are plasma cell tumours that arise outside the bone marrow and are defined by the criteria listed below. They are predominantly found in the head and neck mucosa, especially within the upper respiratory tract, although they can occur in any organ. Local tumour irradiation is the treatment of choice, with nearly all patients successfully achieving local control.
|Criteria for the diagnosis of extramedullary plasmacytoma |
▪ Low concentration or absence of monoclonal protein in serum and/or urine
▪ Extramedullary tumour of clonal plasma cells
▪ Normal bone marrow
▪ Normal skeletal survey
▪ No related organ or tissue impairment (no end organ damage including bone lesions)
Fouquet et al.  assessed the prognostic utility of sFLCs and whole body FDG-PET CT in 43 patients with solitary plasmacytoma. This comprised 33 patients with solitary plasmacytoma of bone and 10 patients with extramedullary plasmacytoma. At diagnosis, 21/43 (49%) patients had an abnormal iFLC concentration and 11/43 (26%) had an abnormal κ/λ sFLC ratio. By univariate analysis, an abnormal iFLC concentration, an abnormal κ/λ sFLC ratio or the presence of ≥2 hypermetabolic lesions on initial PET CT were associated with significantly shorter time to MM progression (Figure 21.5, p=0.002; and data not shown). On multivariate analysis, an abnormal initial iFLC concentration and the presence of ≥2 hypermetabolic lesions on PET-CT were the strongest independent prognostic factors to identify patients at greatest risk of progression to MM. A risk stratification model was constructed in which patients were grouped into 3 categories, based on the presence of 0, 1, or 2 of these risk factors, and median time to MM progression was “Not reached”, 41 or 21 months, respectively (Figure 21.6).