Primary mucinous adenocarcinoma of the posterior mediastinum.

We report a rare case of primary mucinous adenocarcinoma of the posterior mediastinum. A 36-year-old man was referred to our hospital with right flank pain. Computed tomography showed a cystic mass in the posterior mediastinum, and the tumor displaced the diaphragm downward and the inferior vena cava forward. The patient underwent extirpation of the tumor. The cut surface of the resected tumor showed a unilocular cyst filled with abundant gray gelatinous fluid. Microscopically, the tumor had a fibrous capsule lined with cuboidal and columnar malignant epithelial cells with intracellular mucin accumulation and was diagnosed as a mucinous adenocarcinoma.