Epidural Metastasis in Malignant Thymoma Mimicking Epidural Abscess: Case Report and Literature Review

Abstract

Thymoma and thymic carcinoma are rare epithelial tumors that originate from the thymus gland. Extrathoracic metastases occur in the liver, kidney, and bone in 1% to 15% of patients. Although thymoma and thymic carcinoma exhibit highly aggressive biological behavior, spinal metastasis is rare. We describe a 78-year-old man with left wrist and grasp weakness that occurred 7 days before admission. The patient underwent thymoma surgery 7 years ago and was cured. Magnetic resonance images showed a rim-enhanced mass in the C6-7-T1 epidural space. C6-7-T1 laminectomy was performed and the mass was removed. Histological examination was performed and patient was diagnosed with metastatic thymoma. The previous reported case occurred with involvement of the vertebral body or posterior element, but our case was mostly rim-enhanced and appeared as an abscess and intradural extramedullary tumor.

Keywords: Spinal metastasis; Thymic carcinoma; Thymoma.

Fig. 1

Magnetic resonance imaging with contrast of the cervical spine in sagittal (A), coronal (B), and axial (C) planes shows a rim enhancement lesion in left C6-C7-T1 epidural space and low signal lesions in the vertebral bone of C7. Plane radiography in anteroposterior (D), lateral (E) views.

Fig. 2

Malignant thymoma. (A) The tumor shows 2 different components which are separated by fibrous septa (H&E, ×100). (B) The left darker side shows cytokeratin positive epithelial cells admixed with lymphocytes (B2) and the right paler side shows predominant epithelial cells (B3) (cytokeratin, ×100). (C) The nucleus of tumor cells (B3) are variable sized and vesicular and some nuclei show prominent nucleoli (H&E, ×400).

Fig. 3

Metastatic thymoma. (A) The tumor shows sheets of round cells in the background of inflammatory cells (H&E, ×200). The tumor cells are positive for cytokeratin (B, ×200) PAX8 (C, ×200).