# CASE HISTORYA 35-yr-old obese male was admitted to the Tri-Service General Hospital (Taipei, Taiwan) for further examination of an abnormal opacity seen on a chest radiograph obtained during a medical check-up. The patient had been asymptomatic and had never received any treatment with steroids. Physical examination was unremarkable. Laboratory data, including complete blood count and tumour markers, were within normal limits. Abnormal laboratory findings from serological test were as follows: cholesterol 225 mg?dL -1 ; aspartate aminotransferase 45 IU?L -1 ; and alanine aminotransferase 61 IU?L -1 . The initial chest radiograph and computed tomography (CT) scan are seen in figures 1 and 2, respectively.The patient underwent mass resection via sternotomy. An oversized tumoural thymus (the first specimen) was resected in toto. However, the resected tumour was not comparable in size to the lesion discovered on CT imaging. A decision was made to incise the mediastinal pleura for confirmation of the pre-operative CT findings. A sizeable, whitish soft mass (the second specimen) was uncovered in the mediastinum, adjacent to the aortic arch. No attachment was found between the tumour and either the bronchial tree or oesophagus. Surgical excision of the tumour was performed. The histological findings of both specimens are shown in figures 3 and 4. FIGURE 2. Contrast-enhanced computed tomography chest scan cut (mediastinal window) at initial presentation.