[Abnormal branching of left pulmonary artery to the lateral and posterior basal segments].

A 70-year-old male, underwent left lower lobectomy due to lung cancer, had an extremely rare form of left pulmonary artery branching. His pulmonary artery supplying to lateral and posterior basal segments (A9 + 10) was arisen anteriorly from the root of the left pulmonary artery in the mediastinum and ran below in the anterior portion of the upper lobe stem bronchus. Embriologically, this abnormality might be due to a derangement of anastomosis between the pulmonary arch system and splanic plexus in primitive lung, and was interpreted as one of the pulmonary sequestration. Clinically, particularly at thoracotomy, the presence of a large vessel in an unexpected location is very hazardous, so that preoperative pulmonary angiography is useful to detect the abnormal branching.