Rosai–Dorfman Disease (RDD), also known as Sinus Histiocytosis with Massive Lymphadenopathy (SHML), is a rare, benign, proliferative disorder of macrophages and monocytes that was first described by Rosai and Dorfman in 1969. The vast majority of patients present with painless bilateral cervical lymphadenopathy during childhood or young adulthood. The condition is self-limited and rarely requires medical treatment. Involvement of extranodal sites such as eyelids, eye sockets, skin and subcutaneous tissue, gastrointestinal tract, upper airways and central nervous system have been infrequently described. Mediastinal involvement is extremely rare, and there are few cases reported in the literature.

Here, we present a case of a 61-year-old female with a history of mediastinal sinus histiocytosis with massive lymphadenopathy.