Thoracoscopic right S1 + S3 segmentectomy for lung cancer with a displaced B2 bronchus: a case report

Tracheobronchial branching anomalies are uncommon, but increase the risk of intraoperative vascular or bronchial injury if not recognized preoperatively. An independent origin of the right B2 bronchus from the bronchus intermedius is particularly rare and may be accompanied by complex pulmonary venous and arterial variations. Careful preoperative anatomical assessment is crucial when planning anatomical segmentectomy in such cases. A 73-year-old woman was referred to our hospital after a 12-mm partially solid nodule with a cavity at the border between segments S1 and S3 in the right upper lobe was incidentally detected on chest computed tomography (CT). Transbronchial biopsy confirmed squamous cell carcinoma. Bronchoscopy and coronal chest CT showed a displaced right B2 bronchus arising from the bronchus intermedius, with a common B1 + 3 bronchus arising from the right main bronchus. Contrast-enhanced three-dimensional CT bronchography and angiography revealed a complex venous pattern, with V1b draining into the superior pulmonary vein and two additional veins from segment S1 draining into the central vein, as well as a so-called top pulmonary vein formed by a portion of V2 draining into V6. The A3a branch arose from the interlobar pulmonary artery, and no recurrent A2 branch was present. The patient underwent three-port video-assisted thoracoscopic surgery of right S1 + S3 segmentectomy with hilar lymph node dissection. Because the lesion was small and clinically early stage, anatomical segmentectomy was considered feasible provided that an adequate surgical margin could be secured. Despite incomplete fissures between the upper and middle and between the upper and lower lobes, the operation was completed safely by following the preoperative three-dimensional vascular and bronchial roadmap, with careful hilar dissection and indocyanine green-guided identification of the intersegmental plane. The postoperative course was uneventful. The final pathological diagnosis was pT1bN0M0 stage IA2 squamous cell carcinoma, with a pathological surgical margin of 2.7 cm. This case shows that detailed preoperative three-dimensional assessment of the bronchovascular anatomy, including displaced bronchi and atypical pulmonary veins, can facilitate safe anatomical segmentectomy in the presence of rare tracheobronchial anomalies. Such planning is important to avoid vascular injury and to secure adequate surgical margins in segmentectomy for early-stage lung cancer.