plasmacytomas

Plasmacytoma is a localized neoplasm composed of monoclonal plasma cells. It represents a solitary, nonmetastatic proliferation as distinct from systemic disease such as multiple myeloma. Plasmacytomas are classified clinically as solitary plasmacytoma of bone (SBP) or solitary extramedullary plasmacytoma (SEP); a minority may herald evolving myeloma.

SBP arises within bone, most often in the vertebral column or skull, whereas SEP occurs in soft tissues, commonly in the head and neck region, including the nasal cavity, sinuses, oropharynx, and other sites. The tumors typically present in mid to late adulthood with mild local symptoms such as pain or mass effect; extramedullary tumors may cause localized obstruction or symptoms related to mass.

Evaluation to distinguish solitary plasmacytoma from multiple myeloma includes complete blood count, metabolic panel, serum calcium and creatinine, bone marrow biopsy showing clonal plasma cells less than 10%, absence of CRAB features, and imaging studies such as MRI or CT and PET-CT to assess for additional lesions. Serum and urine studies for monoclonal protein, and serum free light chain assay, help characterize the systemic burden.

Treatment consists of local therapy. Radiotherapy is the mainstay for both SBP and SEP, typically delivering around 40–50 Gy; surgical resection may be used when feasible to remove the lesion or relieve compression. Patients require long-term follow-up because progression to multiple myeloma occurs in a subset of cases. If progression occurs, management then follows systemic therapy for myeloma. Prognosis is generally favorable with local control achieved, but outcome depends on risk of progression and extent of disease at presentation.