Solitary Cell Plasmacytoma



What?

• Plasma cell neoplasms can present as a single lesion (solitary plasmacytoma)

• In 3% of patients with MM, the plasma cell proliferation can escape the cellular microenvironment of bone marrow

• Solitary plasmacytoma of bone (SPB) arises from plasma cells of the bone marrow

• Extramedullary plasmacytoma (EMP) arises from the plasma cells of mucosal surfaces



Who?

• Median age 50-70 y/o

• 2/3 Males



Where?

• Occur in bone (plasmacytoma of bone) or outside bone in soft tissues (extramedullary plasmacytoma)



Clinical Presentation:

• SPB presents with pain in the bones containing red bone marrow, e.g., ribs, vertebrae (thoracic more than lumbar and cervical), femur, and pelvis

• EMP can occur anywhere in the body with 80% to 90% in the head and neck region and digestive tract, mainly in the oral cavity, tonsillar fossa, nasal cavity, and paranasal sinuses, which may present with headache, nasal discharge, dysphagia, sore throat, epistaxis, and nasal obstruction



X-Ray Imaging:

• Marked erosion, expansion, and destruction of the bone cortex, sometimes with thick ridging around the periphery, creating a “soap bubble” appearance



Favored Sites for Plasmacytoma:

• Upper respiratory tract (45-80%)

• Mandible

• Ileum

• Vertebrae

• Ribs

• Proximal femur

• Scapula

• Less common - GI tract, liver



SPB - commonly axial skeleton

EMP - head and neck and typically manifests as space-occupying lesions.



Diagnosis?

• Biopsy: Solitary disorder of bone or soft tissue composed of monoclonal plasma cells

• 18F-FDG PET/CT must show no lytic or extramedullary lesions (except for the primary solitary lesion)

• Bone marrow biopsy negative or clonal plasma cells in the bone marrow at a level <10 percent

• No CRAB - no anemia, hypercalcemia, or kidney impairment or of lytic lesions

• Lactate dehydrogenase (LDH) serum levels are increased in patients with EMD myeloma



Diagnostic Evaluation?

• CBC + diff

• CMP, Ca, LDH, beta-2 microglobulin

• SPEP, UPEP, Serum IFE, FLC assay

Pathology:

• Biopsy

• Bone marrow



Treatment?

• Radiation therapy (RT): Radiation doses of 40 Gy or greater are associated with improved local control

• Surgery and chemotherapy as required



Prognosis:

• Median survival time for plasmacytoma averages 10 years

• Solitary plasmacytoma carries a risk of transformation in MM of 10-15% in 3 years

• SEP + Marrow involvement - higher risk 20%



DDX?

• Multiple myeloma

• Waldenström macroglobulinemia

• Non-Hodgkin Lymphoma (NHL)



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