A Rare Case of Extra-Nodal Rosai-Dorfman Disease of the Cheek.

Rosai-Dorfman disease (RDD), which was first reported by Rosai and Dorfman in 1969, is a rare, benign, non-neoplastic proliferation of histiocytes, characterized by painless lymphadenopathy and fever. Lymphadenopathy occurs most commonly in the neck, but also appears in non-cervical lymph nodes or as extranodal lesions. In this case, biopsy of an atypical subcutaneous buccal mass, which was difficult to diagnose preoperatively, led to a diagnosis of RDD. In addition, although lesions were also confirmed in the maxilla, none of the lesions were in lymph nodes; therefore, we ultimately diagnosed the patient with extranodal RDD (ENRDD). Compared with classical RDD, characterized by painless lymphadenopathy and fever, ENRDD is observed only in soft tissue and bone, and occurs mostly frequently among older adults. Cases presenting with lymph node or vital organ lesions also present with systemic symptoms, usually with a progressive and sometimes fatal course. However, RDD localized in soft tissue and bone has a favorable prognosis, and follow-up alone is considered sufficient. Although this case featured epidemiological characteristics of ENRDD, and as there are no fixed therapeutic guidelines, the recommendation is that treatment be considered on a case-by-case basis according to the site and symptoms. There are few reports of ENRDD; therefore, we aim to contribute the details of an additional case to the literature.