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INTRODUCTION
Plasmacytomas are monoclonal proliferations of plasma cells that typically affect the intramedullary axial skeleton1 In rare cases, they may occur first in soft tissues as focal proliferations of tissue and, in even rarer cases, may present as multiple nodules of soft-tissue density2 Typically, multiple myeloma presents with cutaneous manifestations rather than cutaneous plasmacytomas degenerating into multiple myeloma3 Imaging findings of an extramedullary plasmacytoma on radiograph and computed tomography (CT) can be nonspecific and can resemble other entities such as lymphoma, metastases, chondrosarcomas, or giant cell tumors.
CASE REPORT
A 60-year-old female with a medical history of partial complex seizures, hypertension, diabetes, glaucoma, and hyperlipidemia presented with complaints of superficial abdominal pain associated with erythema and swelling for 3 weeks. Physical examination revealed a scaly, indurated 9-cm diameter plaque with 4.5-cm central nodular erythematous tissue in the periumbilical abdomen. Laboratory data showed normal calcium (10.1 mg/dL), normal blood urea nitrogen and creatinine (18 mg/dL and 0.75 mg/dL, respectively), and no evidence of anemia.
CT scan of the patient's abdomen at the time of presentation revealed a 5.8 × 2.7-cm irregularly marginated soft-tissue density just below the umbilicus with an adjacent defect in the midline rectus abdominis (Figure 1). Preliminary pathology suggested lymphoma. Histologically, atypical mononuclear infiltrating fibroadipose and fibrocollagenous tissue and cells demonstrated foamy eosinophilic cytoplasm and oval to slightly irregular nuclear contours with rare Dutcher bodies. Cells were positive for CD79a, CD138, MUM1, and vimentin with kappa immunoglobulin (Ig) light chain restriction. Stain for Ki-67 showed a proliferation index within the tumor cells of 30%. Final pathologic diagnosis was extramedullary plasmacytoma.
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Further workup, including skeletal survey radiograph and spine magnetic resonance imaging (MRI), demonstrated no evidence of metastases. Left iliac crest bone marrow biopsy was negative for multiple myeloma (12% plasma cells). The patient was started on focal radiation therapy (21 cycles) of the abdomen.
Approximately 6 months after completing radiation therapy for the abdominal mass, the patient developed a focal mass-like swelling on her right neck. Following ultrasound-guided biopsy, pathology returned another diagnosis of plasmacytoma. Positron emission tomography (PET)-CT identified an additional pathology-proven medullary plasmacytoma in the left femur that corresponded to a lucency noted on radiograph (Figure 2).
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During the next...