A 59-year-old male with no history of smoking exhibited a slightly increased carcinoembryonic antigen level (5.6 ng/mL) during a health check. Chest computed tomography (CT) revealed a tumor (maximum diameter: 13 mm) in the left lower pulmonary lobe (Fig. 1a). He was referred to our hospital with suspected left lower lobe lung cancer (cT1bN0M0 stage1A2). CT and three-dimensional CT (3D-CT), which was performed using the Fujifilm Synapse Vincent system (Fujifilm Corporation, Tokyo, Japan), revealed the following anatomical anomalies in the left lung: 1) a displaced B1 + 2 running behind the main pulmonary artery, 2) an anomalous V1 + 2 joining the left inferior pulmonary vein (Fig. 2b), and 3) hyperlobulation between S1 + 2 and S3 with a completely fused interlobar fissure between S1 + 2 and S6 (Figs. 1b and 1c). 3D-CT also indicated that the interlobar plane between S1 + 2 and S6 ran perpendicular to the cranio-caudal direction because the volume of S1 + 2 was relatively large (Fig. 2a). Bronchoscopy revealed that three bronchi branched from the left main bronchus (Fig. 1d).
We planned VATS for surgical diagnosis and treatment. Hyperlobulation between S1 + 2 and S3 and a fused fissure between S1 + 2 and S6 were observed (Fig. 3a). At first, we performed non-anatomical wedge resection of the lesion to achieve a rapid pathological diagnosis. The patient was diagnosed with adenocarcinoma, and left lower lobectomy and systematic nodal dissection were performed.
The major pitfalls that we had to pay attention to during this surgery were as follows: 1) to avoid injuring the displaced B1 + 2 running behind the main pulmonary artery and 2) to avoid cutting the anomalous V1 + 2.
The inferior pulmonary vein was identified on the posterior side of the hilum, and the anomalous V1 + 2 joined it (Fig. 3b). To prevent B1 + 2 from being mistaken for B6, we distinguished B1 + 2 from the distal section of B6 on the posterior side (Fig. 3c). The distal branch of A8 was identified using the interlobar fissure. After A8 was divided, we peeled away the pulmonary artery in the proximal direction to identify A6 and V1 + 2, which ran near A6, and a branch of V1 + 2, which ran between S1 + 2 and S6 (Figs. 2b and 3d). This branch was used as a landmark when we divided the fissure between S1 + 2 and the inferior lobe. Forceps were passed from the anterior to posterior side between a branch of V1 + 2 and A6, and the largely fused fissure between S1 + 2 and the inferior lobe was divided using a stapler. After dividing the fissure, A6 and A9 + 10 were identified and divided. The inferior bronchus branched from the left main bronchus at the level of the branches of B3 + B4 + 5 and the displaced B1 + 2, which was located at a more proximal site than normal; therefore, we needed to peel away the bronchus while holding down the pulmonary artery and identified the station 11 lymph nodes. Forceps were passed from the anterior to the posterior side along the station 11 lymph nodes, and the incomplete fissure between S5 and inferior lobe was divided using the stapler. After dividing the fissure, the inferior bronchus was divided, which completed the lobectomy ND2a-2 procedure.
The operation time was 185 min, and 30 mL intraoperative blood loss occurred. Pathologically, the tumor was diagnosed as an invasive mucinous adenocarcinoma with a maximal diameter of 15 mm, and the pathological stage was p-T1aN0M0 stage I A1. The patient’s postoperative course was uneventful, and he was discharged from hospital 6 days after the surgery.