21.1. Introduction

Chapter 21


  • An abnormal κ/λ sFLC ratio at baseline is associated with increased risk of progression to multiple myeloma and reduced overall survival in patients with solitary plasmacytoma of bone.
  • Risk stratification models incorporating sFLC analysis identify solitary plasmacytoma patients at greater risk of progression to multiple myeloma.

Plasmacytomas are isolated clonal proliferations of plasma cells. They are localised to a specific site and do not elicit the typical clinical symptoms associated with multiple myeloma (MM). The estimated incidence rate of all plasmacytomas is 0.34 per 100,000 person years, meaning it is approximately 16-fold less common than MM [469].

In 2003, the International Myeloma Working Group (IMWG) published criteria for the classification of solitary plasmacytoma of bone (SPB), extramedullary plasmacytoma and multiple solitary plasmacytoma as distinct disease entities [470]. These were subsequently adopted by the British Committee for Standards in Haematology [471]. The incidence of SPB has been estimated to be 40% higher than that of extramedullary plasmacytoma [469] and there are distinct differences in the probable outcomes for patients with these diseases.