Plasmocytom

Plasmocytom, or plasmacytoma, is a localized tumor composed of clonal plasma cells. It can arise in bone (solitary plasmacytoma of bone, SPB) or in soft tissue outside the bone (solitary extramedullary plasmacytoma, EMP). These lesions are distinct from multiple myeloma, a systemic plasma cell malignancy; plasmacytoma represents a single lesion with little or no bone marrow involvement.

Most SPBs occur in the axial skeleton, particularly the spine and skull, whereas EMPs arise in mucosal sites such as the upper aerodigestive tract, including the nasal cavity, sinuses, and oropharynx. Symptoms depend on location and may include localized bone pain or mass effect for SPB, and nasal obstruction or epistaxis for EMP.

Diagnosis combines imaging with histopathology and laboratory studies. Imaging includes X-ray, CT or MRI to define extent; a biopsy confirms clonal plasma cell infiltration. Bone marrow biopsy and laboratory tests (serum protein electrophoresis, immunofixation, serum free light chains, and urine immunofixation for Bence Jones proteins) help exclude or identify systemic disease. The presence of CRAB features (hypercalcemia, renal failure, anemia, bone lesions) would favor multiple myeloma.

Treatment typically involves radiotherapy for local control of SPB or EMP; surgery may be used for accessible lesions. Doses of 40–50 Gy are common for solitary lesions. The choice depends on site, size, and completeness of excision. Long-term follow-up is essential, as a portion of solitary plasmacytomas may progress to multiple myeloma over time.

Prognosis is generally favorable with local therapy, but the risk of progression and recurrence exists. Epidemiology shows the condition is relatively rare, predominantly affecting middle-aged and older adults.