Spinal Lumbar Plasmocytoma Mimicking a Schwannoma: A Case Report

Youssef E, Abdelilah I, Naama O and Omar B

Published on: 2024-04-15

Abstract

Solitary bone plasmacytoma (SBP) is a rare disease characterized by a localized proliferation of neoplastic monoclonal plasma cells. We talk about solitary bone plasmacytoma if the lesion originates in bone, most frequently occurs in the axial skeleton, such as vertebra. The most common complaint of patients with such disease is back pain, it can evolve to radiculalgia or even neurological deficit. CT-scan and MRI are crucial to detect bone lesions and neural compressions. It has a higher rate of evolution into multiple myeloma. Radiotherapy is the treatment of choice, Moreover, the role of surgery and chemotherapy is still under debate.

Keywords

Solitary bone plasmacytoma; Lumbar spine; Dumbell shape mass

Case Report

We report a case of a 60 years old male, diabetic and psoriasis under treatment, admitted for the management of a back pain with right S1 radiculalgia evolving for 2 months prior to his admission, the clinical and neurological exam found a right inferior limb monoparesis graded 4/5 with paresthesia, without sphincter disorders. All evolving in a context of conservation of general condition.

Results

The blood work showed no sign of multiple myeloma: no anemia, no hypercalcemia, and no renal function alteration.

MRI was in favor of a lumbar L5S1 right extradural lesion hypointense T1, hyperintense T2, enhacend heterogeneously after gadolinium injection with foraminal extension towards spinal canal in a dumble shape and osteolytic lesions of the right S1 wing.

Patient underwent surgery to decompress the nerve root and to get biopsy for histological study that revealed the lesion was a plasmocytoma.

Figure 1: Lumbar spine MRI showing dumbel shape L5S1 right lesion mimicking a schwannoma, from upleft to downright: lumbar L5S1 right extradural lesion hypo intense T1, HyperintenseT2, enhacend heterogeneously after gadolinium injection with foraminal extension towards spinal canal in a dumble shape with osteolytic lesions of the right S1 wing.

                Figure 2: Intraoperative imaging showing the tumor compressing the thecal sac in the right (suction nozzle and Penfield spatula).

Discussion

Solitary bone plasmacytoma is one of the two subgroups of plasmacytoma, the other being extra medullary plasmacytoma. It is an uncommon plasma cell tumor which localized to bone. It may involve any bone, but have a predisposition for the red marrow-containing axial skeleton, spinal disease is observed in ~50% (range 34-72%) of cases. The peak incidence is in 4th to 6th decades and it is more common in males ~2:1 [1].

Most patients present with skeletal pain or a pathologic fracture of the affected bone, or a neurologic compromise (eg, cord compression) from the start [7].

Solitary bone plasmacytoma originates in bones [2]. The incidence of SBP is approximately 40% higher than extra medullary plasmocytoma [3]. The median age at diagnosis is 55–60 years, significantly lower than in Multiple myeloma (MM) patients and the sex ratio varies from 1,2:1 to 2:1 [2,3,4].

Diagnostic criteria for solitary bone plasmacytoma has been considered as follows [5]:

  • Single area of destruction due to clonal plasma cells
  • Bone marrow plasma cell infiltration <5% of all nucleated cells
  • Absence of osteolytic bone lesions or other tissue involvement (i.e. no evidence of myeloma)
  • Absence of anemia, hypercalcemia or renal impairment (usually attributable to myeloma)
  • Low or absent serum/urine monoclonal protein
  • Preserved levels of uninvolved immunoglobulins.

CT scan can show an expansile lytic lesion with thinned out cortex and characteristic 'mini-brain' appearance has been described in solitary vertebral lesions [6]. This aspect has also been described on MRI [6]. It is seen as curvilinear low signal intensity areas within the lesion, giving an appearance of sulci in the brain.

Signal characteristics include: T1: hypo- to is intense

T2: iso- to hyper intense to muscle, T1 C+ (Gd): variable enhancement [6].

Excision of the tumor and its extent is done, with chemo radiotherapy as an adjuvant. Local recurrence is less than 5% and dissemination is seen in 35-70% of patients. The disease may progress to multiple myeloma, with a bad prognosis [7].

Conclusion

SPB is a rare disease with so many differential diagnosis.

Radiographic features are tricky and can mimic other lesions. Biopsy with histological proof is crucial for diagnosis.

List of Abbreviations

SBP: Solitary bone plasmocytoma

MRI: Magnetic resonance imaging

MM: Multiple myeloma

CT: computed tomography

Gd: Gadolinium

Acknowledgments

No financial support nor personal assistance were received in this work.

Conflict Of Interest

The authors declare that they have no conflict of interests.

References

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