A Rare Case of Mediastinal Masson's Tumor Mimicking a Thymoma.

Masson's tumor or intravascular papillary endothelial hyperplasia is a rare nonmalignant pseudotumoral disease, arising in different anatomic sites, that can clinically and radiologically mimic various benign and malignant tumors. We report an exceptional case of mediastinal Masson's tumor, mimicking a thymoma, in a 48-year-old man, successfully treated with surgery. Though surgical removal may be technically difficult because of the intrinsic hypervascularized nature of these pseudotumoral benign lesions, resection is generally recommended, as they represent a locus minoris resistentiae of blood vessels, potentially causing fatal bleedings.