Solitary Plasmacytoma Workup

Updated: Mar 10, 2021
  • Author: Suzanne R Fanning, DO; Chief Editor: Emmanuel C Besa, MD  more...
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Laboratory Studies

Solitary bone plasmacytoma (SBP)

Although levels are lower than in multiple myeloma, electrophoresis reveals a monoclonal protein in the serum or urine in 24-72% of patients. [34, 20, 35, 36, 37, 38, 21, 39]  Levels of uninvolved immunoglobulin are usually within the reference range. Peripheral blood cell count, kidney function, and calcium are within the reference range.

Extramedullary plasmacytoma (EMP)

Protein electrophoresis shows a monoclonal component in 14-25% of cases. [10, 13, 16] In a series of 46 patients by Galieni and colleagues, all patients had normal uninvolved immunoglobulin levels. [13]  Peripheral blood cell count, renal function, and calcium are within the reference range.


Imaging Studies

Solitary plasmacytoma (SP) shows nonspecific computed tomography (CT) and magnetic resonance imaging (MRI) findings. [40] Fluorodeoxyglucose positron emission tomogrpahy (FDG-PET) is the modality of choice for assessment of the skeletal abnormalities. [40] Whole-body PET/CT or MRI should be performed to exclude the presence of additional malignant lesions; the use of both may provide complementary information. [41] In a series of 43 cases, an abnormal involved serum free light chain (FLC) value and the presence of at least two hypermetabolic lesions on FDG-PET at diagnosis of SP were reported as the two predictors of early evolution. [42]

Solitary bone plasmacytoma 

On plain radiographs, solitary bone plasmacytoma (SBP) classically has a lytic appearance with clear margins and a narrow zone of transition to healthy surrounding bone. [7] Rare occurrences of a cyst, a trabeculated lesion resembling a giant cell tumor or an aneurysmal bone cyst, and sclerotic lesions have been described. [43] The sclerotic lesion is associated with polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes (POEMS) syndrome. [44]

On MRI, the appearance of SBP is consistent with that of a focal area of bone marrow replacement; the signal intensity is similar to muscle on T1-weighted images and hyperintense about muscle on T2-weighted images. MRI is the modality of choice for soft tissue evaluation; also, MRI of the axial skeleton has been shown to be superior to whole-body x-rays and is recommended in patients with SBP of the spine and suspected cord or nerve root compression. [45]

Extramedullary plasmacytoma (EMP)

Radiographic assessment shows local bone destruction in most patients with nasal cavity or maxillary sinus involvement. [16]

Computed tomography (CT) scanning, MRI, and complete endoscopic examination of the aerodigestive and gastrointestinal tracts are required to determine the exact extent of the tumor and its potential for resectability. [15] These lesions may be associated with variable mass effect, infiltration and/or destruction of adjacent bone, muscle, fat, or vascular encasement. [46]


Histologic Findings

A European expert panel recommends that all patients with suspected solitary plasmacytoma undergo bone marrow aspiration and a bone marrow  biopsy to evaluate plasma cell morphology and the degree of total plasma cell infiltration. The degree of clonal plasma cell infiltration should be determined by flow cytometry or by kappa/lambda labeling on bone marrow aspirate or by immunohistochemistry on bone marrow biopsy. [41]

For solitary bone plasmacytoma (SBP), biopsy of the lesion reveals infiltration of the bone by monoclonal plasma cells.

In extramedullary plasmacytoma (EMP), the soft-tissue lesion commonly exhibits submucosal growth; depending on the tumor location, it may require deep biopsy, open biopsy, or complete excision. [15]  The final diagnosis of EMP is made through histological and immunohistochemical features, which demonstrate that the tumor is composed of neoplastic monoclonal plasma cells intensely positive for CD138 and show kappa light chain restriction. [11]  Histologically, EMPs are classified as low, intermediate, or high grade. [24]  Bone marrow biopsy shows less than 5% plasma cells without evidence of clonality. [13]



Wiltshaw classified soft-tissue plasmacytoma into 3 clinical stages, as follows [3] :

  • Stage I – Limited to an extramedullary site
  • Stage II – Involvement of regional lymph nodes
  • Stage III – Multiple metastasis (although it is no longer a solitary plasmacytoma)

The therapeutic and prognostic value of this classification needs further evaluation.