Left S3 + S8 Segmentectomy with Rare Interlobar A3 Vascular Anomaly: A Case Report

Segmentectomy is being accepted as a valid operative procedure for small peripheral non-small cell lung cancer. Understanding pulmonary artery (PA) variations is essential to ensure safe and reliable surgeries. Herein, we report a case of left S3 and S8 segmentectomy involving a complete interlobar branch of the left A3, a relatively rare anomaly reported in less than 0.56% of cases in previous studies.

A woman in her sixties was referred to our hospital with two nodules in the left upper lobe anterior segment (S3, 1.1 × 0.8 cm) and the lower lobe anterior basal segment (S8, 1.8 × 1.7 cm), suggestive of double primary lung cancer. Preoperative thin-slice computed tomography (CT) and three-dimensional CT revealed a vascular anomaly in which the entire left A3 branched from the interlobar PA. Left S3 and S8 segmentectomies were performed via thoracotomy. The interlobar A3 branched at nearly the same level as the A6. After cutting the V3b and V3c veins, the intersegmental plane and the interlobar A3 were sequentially divided using staplers. To prevent torsion of the remaining lung, the edges of the apico-posterior segment (S1+2) and the lingular segment were loosely secured with silk sutures. The operative times were 4 h and 8 min with minimal blood loss. Pathological examination revealed that both nodules were squamous cell carcinomas of the lungs (pT1bN0M0, pStage IA2). The patient remained recurrence-free for over 1 year.

Complete interlobar branching of the left A3 is uncommon. During left S3 segmentectomy in cases involving an interlobar A3, the S1+2 and lingular segments may become solitary blocks, necessitating measures to prevent torsion.