Peripheral primitive neuroectodermal tumor of the thymus.

Peripheral primitive neuroectodermal tumors (pPNET) are an extremely rare disease entity of malignant tumors belonging to the Ewing sarcoma family that usually occur in children and adolescents with a predilection for the truncal and axial soft tissue. Thoracopulmonary manifestation in children mostly involves the chest wall as a large tumorous mass or the posterior mediastinum. In adults these tumors are even more infrequent. We report about a 46-year-old woman with a pPNET of the thymus which infiltrated the pericardium. According to the English literature this is the first reported case both of a thymic pPNET and a pPNET arising in the anterior mediastinum. This illustrates that pPNETs belong to the differential diagnosis of neurogenic mediastinal malignancies not only in the pediatric age population but also in adults and even in so far unknown localizations like the anterior mediastinum.