A rare case of necrotic thymoma.

: The Authors report the case of a patient who underwent resection of a huge anterior mediastinal mass, revealing to be a necrotic thymoma. The patient had been previously submitted to surgical biopsies of the mass yielding non-diagnostic results due to extensive necrosis. A sternotomy was then performed to resect the mediastinal mass originating from the thymus, en-bloc with the mediastinal fat and the apparently infiltrated lung. Histopathology showed a possible cyst/thymoma in massive necrosis, not further definable; revision by a specialized experienced pathologist (J. Rosai) confirmed total mass necrosis and no lung infiltration, thus orientating diagnosis towards a necrotic thymoma and excluding a lymphoblastic lymphoma, with similar histopathological features but more frequent in children or characterized by neoplastic infiltration of surrounding lung. Total body computed tomography (CT) scan and fluorodeoxyglucose positron emission tomography (18F-FDG-PET)/CT, show neither local recurrence, nor distant metastases two years after surgery. In case of anterior mediastinal mass with difficult histopathological diagnosis due to massive necrosis, the hypothesis of a necrotic thymoma should be considered. After radical removal prognosis is generally favourable and no adjuvant treatment is required.