Granulomatous reaction of primary mediastinal seminoma leading to diagnostic delay: a case report.

Primary mediastinal seminoma (PMS) is a rare tumor. PMS can be morphologically related to secondary changes in the form of thymic remnants, cystic degeneration, epithelioid granulomas, fibrotic change, and syncytiotrophoblast-like cells. Ours was an interesting case where a 26-year-old male presented with an incidentally-found anterior mediastinal mass. Even though he had no pulmonary symptoms, the transthoracic co-axial needle biopsy of the mass suggested tuberculosis (TB). However, on follow-up computed tomography (CT) and magnetic resonance image (MRI) in 2 months, the mass slightly increased in size, and a small part of low density or signal intensity appeared, despite the regular anti-TB treatment regimen. Surgical resection was performed, and the resected specimens revealed scattered and irregular-shaped seminoma cells with an intervening chronic granulomatous reaction. The aim of this article is to report a case of PMS in a young male patient who had a granulomatous reaction that mimicked a neoplastic population of cells leading to an erroneous diagnosis of the small biopsy. Therefore, awareness of the secondary changes that can mimic a primary lesion can help with an early correction of this misdiagnosis.