Castleman's disease or angiofollicular lymph node hyperplasia is a rare clinical entity that may present in many sites and with a variety of symptoms. We report here a case of unicentric Castleman's disease (hyaline vascular pattern) located in the mediastinum as a solitary mass. The patient was a Caucasian female 58 years old presented after incidental discovery of the mass in a x-ray. In Castleman's disease surgery is generally recommended for localised lesions to remove the mass as completely as possible reserving other treatment modalities for unresectable cases or multicentric disease.