Rosai–Dorfman Disease with Nodal and Rare Extranodal-thymic and Pancreatic Involvement Documented with 18F-FDG-PET/CT

An 18-year-old male presented with bilateral neck swelling associated with odynophagia and dysphagia, low-grade fever, and weight loss. Ultrasonography (USG) neck revealed suspicious bilateral cervical lymphadenopathy, with USG (A + P) showing multiple abdominal adenopathy. Cervical excision biopsy was suggestive of Rosai–Dorfman disease. Contrast enhanced computed tomography (CECT) neck and thorax showed massive cervical and mediastinal lymphadenopathy. The 18-fluorine-fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT) demonstrated tracer accumulation in the multiple cervical, mediastinal, and abdominal lymph nodes, as well as rare sites of involvement, such as enlarged thymus and pancreas. The patient was started on chemotherapy. Follow-up 18F-FDG-PET/CT for response evaluation showed stable disease status with no new lesions.