[A case of unusual branching and aberrant course of the segmental vein (V2) in the upper lobe of the right lung].

Two right pulmonary veins emptying into the left atrium is the normal state. We describe a case observed at operation in which three pulmonary veins were present on the right side and emptied into the left atrium; a third vein arised from the dorsal part of the upper lobe and followed an abnormal extrapulmonary course. Right lower lobectomy and mediastinal lymph node dissection were carried out for a 73-year-old male with lung carcinoma. At operation, an aberrant branching vein arising from the upper lobe descended dorsally to the right main bronchus and emptied into the left atrium at the middle point between carina and inferior pulmonary vein. The intermediate bronchus lay between the anomalous vein and superior pulmonary vein. Conventional tomogram, CT scan and pulmonary angiogram showed that pulmonary arteries and bronchi were normal in their pattern of branching and distribution, and that the anomalous vein observed at operation was comprised of V2a and V2b according to the system of naming on Yamashita's. Infrequent variations of pulmonary veins are to be kept in mind to that operation may be performed in safety.