Case report
Thymoma metastatic to the extradural spine

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Summary

Background

Spinal epidural metastases are the most common spinal tumor, occurring in 10% of cancer patients. Malignant thymoma is a mediastinal tumor, with extrathoracic metastases occurring in 15% of patients to liver, kidney, and bone. Spinal metastasis is exceptionally rare. We present a case of thymoma with extradural metastasis and discuss the relevant literature.

Case report

We describe a 45-year old man presenting with back pain and hypoesthesia twelve years after a diagnosis of thymoma.

A review of the literature reveals few cases of thymoma metastatic to the extradural spine. We describe a novel surgical approach allowing ventral spinal cord decompression through a posterior incision.

Conclusion

Spinal epidural metastases should be suspected in all cancer patients with back pain. Early detection of epidural metastases may enable improved pain control and preservation of spinal stability, ambulation and sphincter control.

Introduction

Spinal epidural metastasis is the most common spinal tumor, occurring in approximately 10% of all cancer patients.[1], [2] Lung, breast, gastrointestinal and prostate cancer, as well as melanoma and lymphoma are the primary sites accounting for 80% of metastases.3 Most cause bony destruction, although metastatic prostate and breast cancer may cause osteoblastic changes. The most common route of metastasis is hematogenous spread to the vertebral body with erosion posteriorly through the pedicles and into the epidural space. The thoracic spine is the site of 50–60% of epidural metastases. Less than 5% of metastases are intradural or intramedullary.2

Malignant thymoma is a rare, slow-growing, anterior mediastinal tumor. Local invasion and intrathoracic spread are relatively common, and extrathoracic metastases are present in up to 15% of patients, often in the liver, kidney, and bone.4 Approximately one-third of patients with thymoma have myasthenia gravis. Invasive thymomas with a larger component of epithelial cells and association with myasthenia gravis have a poor prognosis.5

The authors describe an unusual case of a 45-year old man with a past history of thymoma presenting twelve years after primary diagnosis with back pain and sensory neuropathy. Review of the literature reveals only a few where thymoma is documented to metastasize to the extradural spine.[4], [5], [6], [7], [8], [9], [10], [11], [12], [13] This case is interesting as the symptoms presented twelve years after primary diagnosis. We also comment on the novel surgical approach of spondylectomy and anterolateral decompression for tumor resection.

Section snippets

Case report

A 45-year old male was referred to the Neurosurgery Clinic in 2002. He complained of progressive back pain and decreased sensation in his toes bilaterally for several weeks. He denied trauma. He had been diagnosed with thymoma in 1990 after presenting with dyspnea. He was subsequently treated with chemotherapy, thymectomy, and local radiotherapy. His course was complicated by hemidiaphragm paralysis. In 1992, he developed myasthenia gravis, for which he was treated with gamma-globulin. He was

Discussion

Spinal extradural metastases are diagnosed preoperatively by radiological studies and clinical examination findings. On MRI, vertebral metastases are usually hypointense compared to normal bone marrow on T1-weighted images and hyperintense on T2-weighted images. Involvement of the posterior vertebral body and pedicle may be apparent on axial views. Pain is the most common presenting symptom, particularly exacerbated by movement, recumbency or straining. Up to two-thirds of patients with spinal

Conclusion

Spinal epidural metastases should be suspected in any cancer patient with back pain that persists in recumbency, even if the patient has been treated with systemic chemotherapy for the primary neoplasm and is believed to be free of disease for a prolonged period of time. Although thymoma is usually a benign tumor, it can be malignant, and therefore should be considered in the differential diagnosis of spinal cord lesions in patients with primary thymoma. Prognostic factors particular to the

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