[Mediastinal pseudotumor-necrotizing and sclerosing mediastinitis with pseudomembranes].

Mediastinal tumors present a rather rare phenomenon with a variety of underlying causes. Important differential diagnoses include benign and malignant tumors as well as idiopathic sclerosing mediastinitis and parasitic infection.Here, we present the case of a mediastinal pseudotumor with compression of the superior vena cava in a young adult male who spent several years abroad in Brazil. Clinicians suspected either a mediastinal lymphoma, malignant mesenchymal tumor, teratoma, sarcoidosis, or tuberculosis. Biopsy tissue failed to provide a definite diagnosis. The subsequently resected mediastinal mass showed a necrotizing, granulomatous inflammation with prominent eosinophilia and sclerosis. Membranous structures were detected in the necrotic areas, which presented as collagen bundles ultrastructurally. Therefore, these membranes were proven to be constituents of lipid pseudomembranes. Consequently the lesion shows characteristics of sclerosing mediastinitis next to characteristics of adipose tissue necrosis with lipid pseudomembranes. Parasitic infection could not be proven.