PMC6360637_01
(a) A chest roentgenogram shows a tumor mass of the right pulmonary hilum and (b) a chest computed tomography scan shows the lesion, measuring 45 mm x 45 mm, is adjacent to the superior vena cava and the ascending aortic with a homogeneous inner component in the right anterior mediastinum.
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A 68-year-old woman who did not exhibit any symptoms, including those of myasthenia gravis or other autoimmune diseases, was found to have an abnormal shadow on her chest roentgenogram at medical check-up (Figure 1(a)) and was referred to our hospital. A chest computed tomography (CT) scan showed a 4.5-cm-diameter tumor with a homogeneous inner component in the anterior mediastinum (Figure 1(b)).
Microscopic examination shows lobular and alveolar structural growth pattern, arranged in epidermoid features with prominent nuclear palisading around perivascular spaces and scant lymphocytes (a), and rosette-like arrangements were observed in part of the tumor (b) (hematoxylin and eosin stain, original magnification x100). Immunohistochemical staining shows that the tumor cells were diffusely positive for synaptophysin (c) and chromogranin (d) (immunohistochemical stain: synaptophysin, x100 and chromogranin, x200).
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Postoperative microscopic examination showed lobular and alveolar structural growth patterns that were arranged in epidermoid features with prominent nuclear palisading around perivascular spaces, and lacking nuclear atypia and scant lymphocytes, and had invaded the pericardium and S3 segment of the right lung, and these findings were consistent with a Masaoka stage III type B3 thymoma, and stage IIIa according to the 8th edition of the International Association for the Study of Lung Cancer and the International Thymic Malignancy Interest Group TNM staging system (Figure 2(a)). However, rosette-like arrangements were observed in part of the tumor (Figure 2(b)); therefore, immunohistochemical examinations were performed. The tumor cells were diffusely positive for synaptophysin (Figure 2(c)) and chromogranin A (Figure 2(d)), but negative for CD5 and c-Kit.