Original Article
Clinical experience of segmentectomy of right middle lobe of lung
2024 Volume 27 Issue 1 Pages 19-24
Details
2024 Volume 27 Issue 1 Pages 19-24
Recently, two phase III randomized controlled trials comparing lobectomy and segmentectomy for peripheral non-small cell lung cancer (NSCLC) of less than 2 cm independently demonstrated non-inferiority of segmentectomy over lobectomy1, 2. Following these results, segmentectomy is expected to be more commonly applied as an alternative procedure to lobectomy for radical resection of early-stage NSCLC. However, segmentectomy of the right middle lobe, which has the smallest volume of all lung lobes, is rarely performed in clinical practice. This procedure is often excluded from clinical trials2, 3, and so the benefits of limited resection of the middle lobe are considered marginal.
We have viewed segmentectomy of the right middle lobe as an option for limited resection in our hospital. Here, we present our experience and discuss its feasibility and safety.
From 2012 to 2023, resection of the lateral segment (S4) was performed for five cases and resection of the medial segment (S5) for one case in our hospital. One of the patients with S4 segmentectomy underwent combined resection of the superior segment (S6). All involved video-assisted thoracoscopic surgery. After resection of the corresponding pulmonary segmental artery, vein, and bronchus, the intersegmental plane was detected using the conventional inflation-deflation method4 for the initial three cases and the indocyanine green fluorescence intravenous injection method5 for the latter three cases. The intersegmental plane between S4 and S5 was divided with a stapling device and the involved segment was resected.
The mean age was 68 ± 6.2. Pathological diagnoses were: primary adenocarcinoma in four, primary squamous cell carcinoma in one, and a benign tumor in one. The tumor size was 20 ± 8.5 mm. The operative time was 146 ± 67 minutes. Postoperative hospital stay was 5.5 ± 1.6 days on average, ranging from 4 to 8 days. There were no severe postoperative complications (Table 1). All patients underwent computed tomography (CT) postoperatively, and the remaining segment of the middle lobe was confirmed to be sufficiently inflated without atelectasis. Postoperative follow-up time was 57 ± 38 months on average, ranging from 9 to 102 months. Two out of five cases with a malignant tumor had a recurrent disease postoperatively.
A 76-year-old female was referred to our hospital because of an abnormal shadow on a chest X-ray. Chest CT revealed mixed ground-glass opacity in the S6 segment of the right lung (Figure 1a). She was diagnosed with adenocarcinoma of the lung by fiber-optic bronchoscopic biopsy. Combined resection of the S6 and S4 segments was performed because the lesion extended from S6 to S4 segments over the major fissure (Figure 1b). The patient was discharged from hospital on the eighth postoperative day without any postoperative complications. She had experienced no recurrence for 11 months after surgery, at which time she was lost to follow-up at our hospital. At 81 months after the surgery, the patient was again referred to our hospital because local recurrence was suspected on CT. However, she refused to have any further examinations or treatments because of a poor general condition.
Mixed ground-glass opacity of more than 3 cm in the S6 segment of the right lung invading the S4 segment (a). An intraoperative image of the lesion extending from the S6 to S4 segment over the major interlobe. Small white triangles indicate the tumor margin (b). RUL: right upper lobe, RML: right middle lobe, RLL: right lower lobe
Case 2.
A 74-year-old male person who had a history of colon cancer surgery five years earlier was referred to our hospital because of an abnormal shadow on a chest X-ray. Chest CT revealed a solid lesion in the right S4 segment with a maximum size of 13 mm (Figure 2a). He had chronic respiratory failure with a forced expiatory volume in 1 second of 33.5%. He underwent S4 segmentectomy because the tumor was suspected to have metastasized from the previous colon cancer, and also because the respiratory function was considered to be inadequate for lobectomy. The patient was discharged from hospital on the fifth postoperative day without any postoperative complications. The pathological diagnosis was adenocarcinoma of the lung with pT1bN0M0 stage 1A2. He was followed up in our out-patient clinic without any adjuvant chemotherapy. At 19 months after the surgery, another tumor was detected in the remaining middle lobe (Figure 2b) and he successfully underwent complete middle lobe lobectomy. The tumor was diagnosed as adenocarcinoma of the lung, but it was difficult to pathologically diagnose whether it was primary or metastatic.
A solid tumor lesion with maximum size of 13 mm in the right S4 segment. (a) A different tumor in the remaining middle lobe detected 9 months after the initial surgery. The frosted area indicates the sufficiently inflated remaining middle lobe (b).
Case 3.
A 72-year-old male, who had a history of left upper segmentectomy for pT2bN0M0 lung adenocarcinoma 38 months earlier, was diagnosed with brain metastasis. He successfully underwent stereotactic radiotherapy. Whole-body screening detected maxillary sinus cancer, which was pathologically confirmed as squamous cell carcinoma by needle biopsy. At the same time, a small nodule in the S4 segment of the right lung, which had been detected six months earlier, was found to have become larger (Figure 3a). A malignant tumor was highly suspected, and S4 segmentectomy with upper mediastinal lymph node dissection was performed (Figure 3b). The tumor was pathologically diagnosed as squamous cell carcinoma of the lung, which was distinct from the maxillary sinus carcinoma in terms of pathological differentiation. Adenocarcinoma was found in the upper mediastinal lymph node, which was considered to be metastatic from the previous left lung cancer. Sufficient inflation of the remaining middle lobe was confirmed by CT performed three months later (Figure 3c). Postoperative chemotherapy was administered for both the lung and maxillary sinus cancer.
An increasing tumor in the S4 segment of the right lung (a). An intraoperative image: S4 was divided using a stapling device and the remaining S5 was sufficiently inflated (b). Postoperative CT showed the sufficiently inflated remaining middle lobe, indicated as the frosted area (c). RUL: right upper lobe, RML: right middle lobe, RLL: right lower lobe, S4: lateral segment, S5: medial segment
The right middle lobe has the smallest volume of all lung lobes, with only two segments. Middle lobe segmentectomy is exceptionally rare because the clinical significance of the procedure is questionable in terms of preservation of the pulmonary function and adequate surgical margins. However, the middle lobe volume varies individually and so its impact on the respiratory function can differ accordingly. Although there have been several case reports of middle lobe segmentectomy6-9, no study has evaluated this controversial procedure in a sufficient number of cases.
In this report, we presented six cases of middle lobe segmentectomy. It should be noted that no serious postoperative complications occurred, such as atelectasis or pneumonia. The middle lobe bronchus is thinner and longer than the other bronchi and lacks horseshoe-shaped cartilage, making it prone to deformity and stenosis. It has been reported that middle lobe torsion is the most common form of pulmonary torsion after lung surgery10. However, postoperative CT confirmed that the residual middle lobe segment in each case was sufficiently inflated. Fixation of the middle lobe to the adjacent lung lobe is considered useful to prevent middle lobe torsion11, 12. Although the remaining middle lobe was not fixed, the opposite side of the interlobar fissure was not divided by the fissureless technique and remained intact, which may have partly contributed to avoiding bronchial torsion.
In this study, five of the six cases had lung carcinoma involving the right middle lobe. All tumors were located within the inner two-thirds of the lobe, and so wedge resection was difficult to perform with a sufficient surgical margin. Two cases (cases 1 and 2) had recurrent disease after surgery with a negative surgical margin. However, the main tumor was in S6 in case 1 and local recurrence occurred on the stump following S6 resection. In case 2, the heterochronous cancer in the remaining middle lobe, which was not detected prior to the first surgery, was not adjacent to the stump of the resection. Due to the small number of cases in this report, it is impossible to come to a definitive conclusion about the curative effect of middle lobe segmentectomy for malignant tumors. However, segmentectomy of the right middle lobe is practically possible to perform in terms of postoperative safety and may contribute to preservation of the postoperative pulmonary function, with sufficient inflation of the remaining segment.
In conclusion, segmentectomy of the right middle lobe is technically possible to perform for specific patients with small lesions, for whom it is difficult to conduct wedge resection. However, the clinical benefits, especially in terms of the curative effect and preservation of the lung function, need to be further evaluated based on additional clinical experiences.
The authors declare that no conflict of interest exists.
