Intradural, extramedullary spinal cord granular cell tumor: a case report and clinicopathologic review of the literature.

Granular cell tumor (GCT) of the spine is uncommon, with intradural extramedullary location being exceptionally rare. The non-specific clinical presentation and variable histologic patterns can make recognition of this tumor challenging. Two previous reports of GCT of the spine were reviewed (Medline 1960-2009) and analyzed with respect to this case report. The patients included two women and one man (mean age, 28.7 years). Patients presented with 3 to 4 months of lower back pain and/or lower extremity radiculopathy. The lesions appeared radiographically to be intradural and extramedullary or intramedullary. The tumors were found at T10 or L1-L2 space. Radiographically, all tumors enhanced homogenously on T1 post-gadolinium imaging with a mean tumor size of approximately 1.6 cm. Histologically, the tumors were composed of large, polygonal granular cells. The abundant cytoplasm was fine or coarsely granular, surrounding small, pale-staining nuclei, which were eccentrically located in the cell. The tumor cells were periodic acid Schiff positive, diastase resistant, and were positive with S-100 protein, CD68, inhibin, and neuron-specific enolase immunohistochemistry. The clinical and histologic differential diagnosis includes schwannoma, neurofibroma, meningioma, astrocytoma, melanocytoma, and metastatic tumors. Patients were managed with excision. One patient had symptomatic and radiographic local recurrence that was subsequently treated with radiation, resulting in stabilization of disease and symptoms. Intradural GCTs of the spine are rare and radiographically indistinguishable from tumors that more commonly arise in this location. Histologic recognition of this rare tumor is important because the subsequent clinical course of the disease differs from other similar lesions.