Myelomassa

Myelomassa, or a myeloma mass, is a focal lesion composed of clonal plasma cells associated with plasma cell dyscrasias such as multiple myeloma or solitary plasmacytoma. The term describes a mass that can occur in bone (bone plasmacytoma with skeletal involvement) or in soft tissue (extramedullary plasmacytoma).

Clinical features depend on location. Bone lesions commonly cause persistent bone pain, tenderness, pathologic fracture, and can contribute to anemia, hypercalcemia, and kidney dysfunction when systemic myeloma is present. Soft-tissue masses may present as localized swelling or mass effect.

Diagnosis relies on tissue biopsy showing clonal plasma cells, with immunohistochemistry typically positive for CD138 and evidence of light-chain restriction. Evaluation includes marrow biopsy, serum and urine studies for monoclonal protein, free light chains, and imaging (X-ray, CT, MRI, PET-CT) to assess extent and other lesions. Staging follows guidelines for myeloma and considers systemic involvement.

Management depends on whether the mass is solitary or part of systemic disease. Solitary extramedullary plasmacytoma or solitary bone plasmacytoma is typically treated with local radiotherapy, sometimes with surgical excision. When myeloma is systemic, treatment targets the underlying plasma cell disorder using combinations of proteasome inhibitors, immunomodulatory drugs, corticosteroids, and sometimes alkylating agents or autologous stem cell transplantation in eligible patients; local therapy may be used as an adjunct.

Prognosis varies. Solitary plasmacytoma without systemic disease has relatively favorable outcomes with local control; extramedullary involvement in myeloma is associated with higher relapse risk and shorter survival.