Rosai-Dorfman disease presenting as isolated cervical lymphadenopathy in a young adult: A case report.

Rosai-Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy, is a rare non-Langerhans cell histiocytic disorder most commonly involving the cervical lymph nodes, which are affected in approximately 80%-90% of cases. It predominantly affects children and young adults but may occur at any age, typically presenting with painless, bilateral, and sometimes bulky cervical lymphadenopathy, occasionally associated with systemic inflammatory symptoms and laboratory abnormalities such as elevated inflammatory markers and polyclonal hypergammaglobulinemia. Histopathological examination is essential for diagnosis and demonstrates marked sinus expansion by large histiocytes with abundant pale cytoplasm and characteristic emperipolesis, set within a lymphoplasmacytic background. Immunohistochemically, these histiocytes express CD68, CD163, and S100 protein, while lacking CD1a and langerin expression, allowing distinction from other histiocytic disorders. Although historically considered a benign reactive condition, recent molecular studies have identified activating mutations in the MAPK/ERK signaling pathway, including KRAS, NRAS, and MAP2K1, in a significant subset of cases, supporting a clonal neoplastic component. The clinical course of cervical RDD is generally favorable, and management is individualized, ranging from observation to surgical excision in cases of compressive symptoms, with systemic or targeted therapies reserved for refractory or multisystem disease. We report the case of a 25-year-old patient with no significant past medical history who presented with a persistent cervical lymphadenopathy. Comprehensive clinical evaluation, laboratory investigations, and imaging studies supported the diagnosis of Rosai-Dorfman disease. Prompt recognition and appropriate surgical management play a crucial role in achieving favorable clinical outcomes.