PET/CT-negative malignant spine tumor with pathologic fracture: A case report of malignant solitary bone plasmacytoma.

Rationale: We report on a patient with a positron emission tomography/computed tomography scans (PET/CT)-negative malignant spine tumor, which had even caused a pathologic fracture, and was eventually confirmed on surgical biopsy. Patient concerns: A 67-year-old man visited our emergency department with sudden onset of lower extremities paraplegia after slip down. On examination, gradually increasing paralysis was observed in both lower limbs. Diagnoses: Plain radiograph and CT showed an acute burst fracture at T12 with an osteolytic mass lesion within the vertebral body and pedicle, causing severe encroachment of the spinal canal. Magnetic resonance imaging (MRI) revealed a bulging posterior cortex of the T12 vertebral body, which suspected a pathologic fracture due to malignancy. However, PET/CT showed a benign burst fracture, which was confirmed by a senior radiologist. Intervention: We planned surgery for emergent decompression of the spinal cord, temporary stabilization, and tissue biopsy. The histologic evaluation confirmed the lesion to be a malignant solitary bone plasmacytoma (SBP). Seven days later, definite surgery in the form of pedicle screw fixation and posterolateral bone graft from T8 to L2 was performed. Four weeks after the definite surgery, the patient underwent radiation therapy for 2 months. Outcomes: Three weeks postoperatively, lower extremity motor function fully recovered, and ambulation with support was possible. One year postoperatively, spine MRI showed no evidence of local recurrence, and complete decompression of the spinal cord was achieved. Lessons: Spine surgeons should bear in mind that malignant spine tumors could be misinterpreted as benign on PET/CT.