Multifocal intra-cranial masses: Late presentation of an uncommon histiocytic disorder.

We present a case of a 59-year-old female with headaches and memory loss. Her history includes surgeries for hydronephrosis and a mediastinal mass initially diagnosed as retroperitoneal fibrosis. Imaging performed a few years later revealed multiple bilateral supratentorial masses. Biopsy confirmed Erdheim-Chester Disease (ECD), a rare, non-Langerhans cell histiocytosis with multi-system involvement, expression of histiocyte markers CD68 and CD163, and a mutation. This case emphasizes the importance of considering rare conditions in differential diagnoses and using a multimodal approach that integrates clinical, radiological, and histopathological data. Early identification and tailored treatment, including targeted molecular therapies, can significantly improve patient outcomes.