FDG-PET/CT Avid Uptake of a Biopsy-Proven Aggressive Melanotic Schwannoma of the S2 Spinal Nerve Root

Malignant melanotic nerve sheath tumors (MMNSTs), also known as a melanocytic schwannoma (MS), are a rare type of peripheral nerve sheath tumors including Schwann cells with melanocytic differentiation. Only a few cases of spinal MMNST have been reported in literature. Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ( ¹⁸ F-FDG-PET/CT) could be used to detect these lesions. A 70-year-old man with a 6-month history of backache was admitted to our hospital. PET/CT showed a paravertebral soft tissue mass along the spinal nerve at the S2 level with strong FDG uptake, and a nodule with increased FDG uptake in the right lobe of the left liver. A CT-guided biopsy of the S2 lesion was performed. The final diagnosis was spinal MS with hepatic metastasis. The patient received stereotactic body radiation therapy. Herein, we report the PET/CT findings of a case of MS with hepatic metastasis. FDG-PET/CT is helpful in the differential diagnosis of benign and malignant lesions although nonspecific.