Uncovering Rosai-Dorfman Disease through histopathology in a middle-aged man: a case report

Rosai-Dorfman disease is a rare and benign histiocytic proliferative disorder characterized by accumulation of large S100- positive histiocytes, which typically show emperipolesis. The diagnosis can be challenging due to its rarity and diverse clinical presentations, often mimicking malignancies. We report a case of a 58-year-old man presenting with painless right cervical lymphadenopathy accompanied by intermittent low-grade fever for three months. Fine needle aspiration cytology from the node was initially misinterpreted as suspicious for Hodgkin lymphoma due to the presence of scant binucleated reactive histiocytes resembling Reed-Sternberg like cells. However, histopathological examination of an excised lymph node showed Rosai-Dorfman disease with additional confirmation provided by immunohistochemistry. Differentiating Rosai-Dorfman disease from malignancies requires a high level of clinical suspicion due to overlapping features. This case emphasized the diagnostic pitfalls in cytology and the importance of histopathological confirmation. Increased awareness of Rosai-Dorfman disease can prevent misdiagnosis and avoid unnecessary invasive procedures and treatment.