An extremely rare case of Rosai–Dorfman disease in the thymus

BACKGROUND: There were very few reports of Rosai–Dorfman disease in the thymus, which known as sinus histiocytosis with massive lymphadenopathy. It usually accompanied with other systemic symptoms such as fever, malaise, night sweats, or weight loss in the short term. Case presentation We herein report a rare case of RDD of thymic origin and a review of the literature concerning the clinical and pathological features of this disease, which is often misdiagnosed as thymoma. The patient was underwent thymectomy to extirpate the lesion completely by video-assisted thoracic surgery. CONCLUSIONS: To the best of our knowledge, this is the fourth thymus occurring RDD case with proof via histology and IHC. Our findings suggest the difficulty of making a diagnosis before surgery and more cases will need to be reported in order to facilitate the preoperative diagnosis of such a rare tumor.