Introduction and epidemiology
Solitary plasmacytoma, which accounts for less than 5% of plasma cell dyscrasias is characterized by a localized proliferation of malignant plasma cells in the absence of evident disease elsewhere. Such a proliferation may arise in a bone (solitary bone plasmacytoma or SBP) or an extra-medullary compartment (extramedullary plasmacytoma or EMP). Plasmacytomas may also arise in a multifocal manner without evidence of malignant plasma cells in the intervening tissues. Extra-medullary plasmacytomas may also arise in the context of multiple myeloma.
Solitary Bone Plasmacytoma
SBP may arise at any age, but the median age of onset at 55 years is 10 years younger than that for myeloma, with a 1.87:1 male to female ratio[1].
Clinical and laboratory features
In two-thirds of cases, SBP arises in the axial skeleton, including the spine (thoracic > lumbar > sacral > cervical spine), skull, ribs and sternum and, in one-third, the appendicular skeleton, including the shoulder girdle, pelvic girdle or the extremities [2]. Localized skeletal pain due to the solitary osteolytic lesion is a typical presentation of SBP. If the spine is affected, spinal cord or nerve root compression may be an important clinical consequence. Other presentations include pathological fracture of the affected bone, a soft tissue mass due to extra-medullary extension of the tumor and in a small proportion, symptoms of peripheral neuropathy.