Abstract
A 76-year-old man took a chest X-ray for his medical checkup and an abnormal shadow was detected in the right lower lung field. For more detailed examination, he was referred to our hospital. Chest computed tomography showed a 20-mm nodule with relatively regular margins in the right lower lobe. A compact proliferation of circular to polygonal cells with a high nucleus-cytoplasm ratio was evident in a transbronchial lung biopsy. Based on pathological findings, a mature large B-cell lymphoma was diagnosed. Thoracoscopic right lower lobectomy and mediastinal lymphadenectomy were performed. The post-surgical pathological examination showed that the tumor consisted of diffuse to compact proliferation of medium to large atypical lymphocyte-like cells. Immunohistochemical staining yielded positive results for B-cell lineage markers. Five months after surgical resection, neither local recurrence nor accumulation in remote organs was observed on gallium scintigraphy. The diagnosis of primary pulmonary diffuse large B-cell lymphoma was established.