Erdheim-Chester Disease Presenting as an Anterior Mediastinal Tumor without Skeletal Involvement.

Erdheim-Chester disease (ECD) is a form of non-Langerhans cell histiocytosis that most commonly involves the skeletal system. We report an unusual case of ECD presenting as an anterior mediastinal tumor without skeletal involvement. A 60-year-old man with no remarkable medical history was referred for evaluation of a mediastinal mass. The patient underwent surgical excision of the tumor via video-assisted thoracoscopic surgery. Histologic examination revealed marked proliferation of atypical histiocytes with sclerosis, and the results of immunohistochemical staining were suggestive of ECD.