Thymic Rosai-Dorfman disease infiltrating lung tissue: a case report

Rosai-Dorfman disease (RDD) is a rare histiocytic disorder with an incompletely defined etiology and a relatively benign prognosis, typically presents with painless massive lymphadenopathy. Isolated mediastinal RDD with an invasive biological behavior is extremely rare and lacking specific clinical manifestations other than histological examination. Here we present a 38-year-old male who complained self-limited chest pain and chest CT revealed a right anterior mediastinal mass. The thymic mass was found to present an invasive behavior into the right lung during surgery, while post-operative pathology exam of the mediastinal mass and part of the lung tissue confirmed the diagnosis of RDD. To our knowledge, this case presents an isolated intrathoracic RDD mimicking thymoma and involved more than one organ, which has not been reported previously.