18 F-FDG PET/CT in Pediatric ALK-Positive Histiocytosis With Isolated CNS Involvement.

An 11-year-old girl presented with focal impaired awareness seizures. MRI brain demonstrated a T2 hyperintense cortical lesion in the left temporal lobe with surrounding vasogenic edema. 18 F-FDG PET/CT was arranged to assess metabolic activity of the cerebral lesion, to screen the whole body for other metabolically active lesions, and to assist biopsy planning. The study demonstrated intensely increased FDG uptake within the left temporal lobe lesion without evidence of hypermetabolic lesions elsewhere on the whole-body acquisition. The brain lesion was excised, and histopathology and molecular testing were consistent with ALK-positive histiocytosis.