Extradural nodular fasciitis arising in the spinal canal

STUDY DESIGN.: Case report. OBJECTIVE.: To describe a patient with nodular fasciitis arising in the lumbar extradural space. SUMMARY OF BACKGROUND DATA.: Nodular fasciitis is a benign proliferation of fibroblasts and myofibroblasts. It commonly occurs in the subcutaneous tissue of an upper extremity, trunk, head, and neck, but rarely arises in the spinal canal. METHODS.: A 7-year-old boy experienced gradually increasing intense radiating pain from the bilateral buttocks to the lower extremities after a bruise on his lower back. Computed tomography and magnetic resonance imaging demonstrated a relatively circumscribed mass in the dorsal epidural space from the first lumbar vertebra (L1) to L2. The presumptive diagnosis based on the radiologic findings included aggressive neoplasm such as extraskeletal Ewing sarcoma/primitive neuroectodermal tumor or malignant lymphoma. RESULTS.: The patient underwent L1-L2 laminectomy and resection of the tumor. Histologically, the tumor was mainly composed of a proliferation of spindle cells without atypia, positive for vimentin and smooth muscle actin, and myxoid areas with a loosely textured feathery pattern. These findings are the typical features of nodular fasciitis. Surgery relieved the patient's pain, with no evidence of recurrence at a recent 4-year follow-up. CONCLUSION.: This report presents a very rare case of extradural nodular fasciitis arising in the lumbar spinal canal, which could have been misinterpreted as a malignant tumor such as extraskeletal Ewing sarcoma/primitive neuroectodermal tumor because of its rapid growth and absence of distinguishing radiologic features. A detailed histopathologic examination including immunohistochemistry is important for the correct diagnosis.