[A case of asymptomatic paraganglioma diagnosed by abnormal shadow on chest X-ray].

A 65-year-old man was noted to have an abnormal shadow on chest X-ray at mass screening examination, and was seen at Douhoku Byoin National Sanatorium. Chest X-ray showed a homogeneous mass shadow and a lytic lesion of the right 5th rib with extra-pleural tumor sign at the right upper and middle lung fields. Retroperitoneal tumor of 5 cm in diameter was detected in the right adrenal area by ultrasonography. Because of increasing plasma levels of norepinephrine and dopamine, the diagnosis of malignant pheochromocytoma with rib metastasis was made. Histologically, chromogranin staining was positive in each resected specimen. The retroperitoneal tumor was separate from the right adrenal gland. We report a rare case of malignant paraganglioma which was asymptomatic in spite of increasing plasma levels of catecholamines.