18FDG PET/MRI in Histiocytic Sarcoma of the Spinal Canal

Histiocytic sarcoma is a malignant neoplasm of mature histiocytes that rarely involves the central nervous system. A 49-year-old man presenting with a mass filling the lumbar spinal canal underwent 18 F-FDG PET/MRI. Fused PET/MRI images showed intense FDG uptake in the mass, as well as uptake in the cerebellopontine angle and cervical lymph nodes. Biopsy of the spinal lesion showed histiocytic sarcoma. This is the rare case report of PET/MRI performed for histiocytic sarcoma demonstrating changes in FDG uptake during chemotherapy. This case highlights the utility of PET imaging for evaluating the extent of lesions and treatment efficacy for histiocytic sarcoma.