Synchronous Mediastinal and Central Nervous System Involvement in Rosai-Dorfman Disease: A Case Report.

Rosai-Dorfman disease (RDD) is a rare disorder characterized by the proliferation and accumulation of histiocytes, primarily within lymph node sinuses. Uncommonly, other extranodal sites, such as the central nervous system, can also be affected. Here, we document the case of a 61-year-old woman presenting with dizziness, confusion, and headaches. Magnetic resonance imaging (MRI) showed an extra-axial avidly enhancing mass in the left parietal region presumed to be a meningioma based solely on its imaging appearance. The patient underwent surgical resection, and histopathological examination showed enlarged histiocytes positive for S100, CD68, and CD163 and negative for CD1a, consistent with RDD. She was followed up with a positron emission tomography/computed tomography (PET/CT) to evaluate other disease activity sites. A single mediastinal node was identified adjacent to the atriocaval junction intensely fluorodeoxyglucose avid. The patient underwent robotic node excision, with pathology analysis compatible with RDD. We emphasize the need to increase recognition of RDD on differential brain lesions, especially meningiomas, and suggest PET/CT as a valid tool to search for other disease activity lesions.