Benign notochordal cell tumor of the lung: Report of a case

A surgical case of a benign notochordal cell tumor of the lung is reported. The patient was an asymptomatic 41‐year‐old man, who was incidentally found to have a small tumor in the subpleural region of the left lingular segment. Since wedge resection of the tumor, the patient has been free from recurrence. The tumor measured 12 mm in diameter and showed a central cystic change. It consisted of a diffuse proliferation of polygonal cells with abundant, uni‐ or multi‐vacuolated cytoplasm and bland nuclei. The tumor did not show a lobular architecture and lacked a myxoid or fibrous connective tissue containing blood vessels. In the peripheral region of the tumor, a small number of alveolar epithelial cells were entrapped. The nuclei of tumor cells were immunoreactive for brachyury, and the cytoplasm was positive for cytokeratin and S‐100 protein. The entrapment of alveolar epithelial cells suggests infiltrative growth of the tumor, and the almost complete absence of blood vessels within the tumor may have restricted tumor growth and induced a cystic change in the central region.