Solitary T12 Plasmacytoma Presenting with Severe Back Pain and Spinal Instability: A Case Report and Review of the Literature

Abstract

Background: Solitary plasmacytoma of bone (SPB) is a localized proliferation of monoclonal plasma cells without systemic myelomatous involvement. The thoracic spine is an uncommon site, and when affected, patients may present with pain and mechanical instability. Early diagnosis and multidisciplinary management are vital to prevent neurological deterioration and systemic progression (1,2). Case Description: A 42-year-old male presented with progressive lower back pain over three months, aggravated by posture. Neurological examination was normal. MRI revealed pathologic fracture of the T12vertebral body with mild angulation. The T11/T12 and T12/L1 intervertebral discs are intact. Classic mini rain appearance noted. CT-guided biopsy confirmed solitary plasmacytoma Skeletal survey ruled out any other skeletal lesions. Labs had no features of multiple myeloma or any other plasma cell dyscrasias.  The patient underwent posterolateral transthoracic T12 corpectomy and expandable cage fusion. Histopathology confirmed the diagnosis.  At one 1 month follow up he’s neurologically intact and pain free and radiologically stable Referred for adjuvant radiotherapy (40 Gy in 20 fractions). Discussion: Solitary plasmacytoma represents about 5–10% of plasma cell neoplasms (3). The thoracic spine is the most frequent site of involvement due to rich marrow content and venous plexus drainage (4). MRI typically shows an isointense to hypointense lesion with homogeneous enhancement (5). Definitive local control is achieved with radiotherapy doses of 40–50 Gy, with surgery indicated for instability or compression (6,7). Persistent M-protein, abnormal light chain ratios, and specific cytogenetic markers predict progression to multiple myeloma (8). Long-term follow-up is mandatory since up to 50–70% of patients may develop systemic disease (9,10). Conclusion: Solitary thoracic plasmacytoma should be considered in patients with destructive vertebral lesions and instability. Combined surgical stabilization and radiotherapy provide optimal outcomes for pain relief, local control, and prevention of deformity. Vigilant follow-up is essential to detect progression to multiple myeloma.