RESUMO
Primary mediastinal seminomas are rare tumors. Morphologically, they can be associated with secondary changes in the form of thymic remnants, cystic change, epithelioid granulomas, abundant fibrosis, and syncytiotrophoblast like cells. Ours was an interesting case where a 17‑year‑old adolescent male presented with anterior mediastinal mass. Fine needle aspiration and trucut biopsy of the mass favored tuberculosis; however, he did not respond to antituberculosis treatment regime. He was subjected to video‑assisted thoracoscopic surgery and the histopathological examination along with supportive immunohistochemistry of the mass revealed scattered seminoma cells which were being masked by extensive granulomatous reaction. The aim of this article is to report a case of primary mediastinal thymic seminoma in a young male associated with extensive granulomatous reaction masking the neoplastic population of cells leading to erroneous diagnosis on small biopsy.