Rosai-Dorfman Disease: A Differential Diagnosis for Tonsillar Asymmetry.

Rosai-Dorfman disease (RDD) is a rare histiocytic disorder that classically presents with massive cervical lymphadenopathy. We report the case of a 38-year-old Indian man referred to the ear, nose, and throat (ENT) clinic via the urgent cancer pathway with a persistent sore throat and unilateral tonsillar hypertrophy, without cervical lymphadenopathy. Clinical examination demonstrated an isolated, firm, non-ulcerative swelling of the right tonsil. Cross-sectional imaging confirmed tonsillar asymmetry without evidence of local invasion or metastatic disease, although increased uptake was noted on positron emission tomography (PET). The patient underwent bilateral tonsillectomy, and histopathological analysis demonstrated large histiocytic cells with immunohistochemistry positive for S100 and CD68 and negative for CD1a, confirming RDD. Subsequent multidisciplinary follow-up identified additional manifestations of the disease, including lung nodules and cutaneous lesions, and the patient remained under the care of the haematology histiocytosis clinic. This case highlights the importance of considering RDD in the differential diagnosis of tonsillar asymmetry and its implications for optimising multidisciplinary patient care.