18F-FDG PET/CT Findings in a Patient With Isolated Intracranial Rosai-Dorfman Disease

Rosai-Dorman disease (RDD) or sinus histiocytosis with massive lymphadenopathy is a rare histiocytic disorder first described in 1969. RDD involving the central nervous system is considered to be rare, with fewer than 120 cases reported in the literature. We present a 51-year-old woman with a history of panhypopituitarism, episodic memory disturbance, and a hypothalamic tumor. Stereotaxic hypothalamic lesion biopsy showed histiocytic proliferation positive for S100 protein and CD68+, but negative for CD1a, typical for RDD. 18F-FDG PET/CT 4 months later demonstrated increased hypothalamic metabolic activity.