Review Question - QID 215548

This patient has an incidental finding of a thoracic spine osteochondroma arising from the transverse process. These lesions form secondary to aberrant cartilaginous growth.

Osteochondromas are the most common benign bone tumor and are often asymptomatic. When they are symptomatic they most often present in adolescents and young adults. Most often they present around the knee (distal femur and proximal tibia), proximal femur, and proximal humerus. While the exact pathologic process that gives rise to solitary osteochondromas is not fully understood, they are a hamartomatous proliferation of bone and cartilage. They will have continuity with the intramedullary canal. Multiple hereditary exostoses is an autosomal dominant genetic disease characterized by numerous osteochondromas and is associated with the EXT1, EXT2, and EXT3 genes.

Yakkanti et al. present a case series of 4 patients with solitary osteochondromas. All lesions arose from the posterior column, with one extending into the middle column. Treatment of symptomatic cases was by posterior approach with marginal excision. Their literature review found 132 cases, with 27.7% presenting with myelopathic symptoms and 52.2% arising in the cervical spine.

Sade et al. present a case report of a 15-year-old female with osteochondroma of the lumbar spine. They discuss MRI findings which classically demonstrate iso-intensity between the central portion of the mass and noninvolved bone on T2-weighted imaging, as well as continuity of the mass with the medullary component of the vertebra. Additionally, the peripheral (cartilage) component is hyper-intense on T2 due to the high water content of cartilage. They further discuss these lesions are very rare and often asymptomatic.

Figure A demonstrates an axial CT cut through a thoracic vertebra with an osseous growth involving the transverse process without evidence of fracture with apparent continuity with the intramedullary aspect of the vertebra.

Incorrect answer:
Answer 1&5: With a penetrating or blunt-force trauma you would expect the involvement of the other structures nearby. Additionally, Figure A demonstrates increased bone in the region which would not be expected with trauma.
Answer 3: Prior to his injury, this patient was otherwise healthy without back pain. It would be expected he would have had antecedent back pain in the setting of infection. Additionally, spinal infections more often involve the vertebral body or intervertebral disk.
Answer 4: Based upon the patient's CT scan, it is unlikely this is a malignant process as there is no surrounding soft tissue mass and the edges are well defined.