Rosai-Dorfman Disease Presenting as a Bone-Destructive Mass in the Maxillary Sinus With Orbital Extension: A Diagnostic and Therapeutic Challenge.

Rosai-Dorfman disease (RDD) is a rare histiocytic disorder characterized by massive lymphadenopathy and, in some cases, extranodal involvement, resulting in significant functional impairment. Maxillary sinus lesions with orbital extension are extremely rare and may mimic malignancy. We report the case of a 76-year-old man who presented with left lower eyelid swelling and diplopia. Computed tomography revealed a mass centered in the left maxillary sinus, extending into the orbit and buccal subcutaneous tissue, accompanied by osteolytic changes. Serologic testing, including soluble interleukin-2 receptor (sIL-2R) and immunoglobulin G4 (IgG4) level, was unremarkable. An initial nasal biopsy suggested chronic inflammation; however, surgical excision was performed due to concerns about malignancy. Histopathology revealed S-100- and CD68-positive histiocytes exhibiting emperipolesis, confirming a diagnosis of RDD. The patient was treated with oral corticosteroids (prednisolone 1 mg/kg/day), resulting in rapid symptom resolution without recurrence over an 18-month follow-up period. This case highlights the importance of including RDD in the differential diagnosis of bone-destructive maxillary sinus lesions. Although RDD is not a malignant tumor, it can cause significant functional impairment. Corticosteroids appear to be an effective treatment option. Early diagnosis and appropriate steroid therapy may lead to excellent outcomes while avoiding overtreatment.