Long-term Follow-up in a Patient with Segmentectomy for Lung Cancer Developed in the Segment with Displaced Left B¹⁺² Bronchus

A B S T R A C T

A 62-year-old woman was admitted with a 20 mm diameter tumor in the left upper lobe of the lung. Preoperative computed tomography (CT) revealed a displaced anomalous B¹⁺² arising from the left main bronchus. In addition, an accessory fissure was detected between the apicoposterior (S¹⁺²) and anterior (S3) segments. As the lesion was entirely contained in the S¹⁺², we performed video-assisted thoracic surgical S¹⁺² segmentectomy with systematic lymph node dissection. During the operation, we easily detected and successfully divided the displaced B¹⁺² located behind the left main pulmonary artery. The pathological diagnosis was invasive adenocarcinoma with T1bN0M0 (TNM 8th edition). Histologically, neither lymphatic invasion nor vascular invasion was detected in the invasive area of the tumor. If regional lymph node dissection with appropriate intraoperative histologic examination by frozen section could be made, segmentectomy may be an acceptable, optional procedure with curative intent for cancer patients with such an anomaly.

K E Y W O R D S

Displaced left B¹⁺² bronchus, segmentectomy, lung cancer

Introduction

A comprehensive preoperative evaluation of the lung anatomy is essential for preventing unexpected intraoperative complications due to bronchial and vessel anomalies. According to the review of bronchographies of 13,222 cases, there were only two cases (0.015%) with the displaced left B¹⁺² [1]. Moreover, lung cancer originating from the apicoposterior segment (S¹⁺²) with a displaced left B¹⁺² is extremely rare, and there is no standard surgical procedure for such a combination. We herein report the successful treatment of a patient with lung cancer combined with a displaced left B¹⁺² based on precise preoperative anatomic information and long-term postoperative follow-up.

Case Report

A 62-year-old woman had been referred to another hospital because of an abnormal shadow on screening chest radiography. She had no symptoms. Serum tumor markers were not elevated. Computed tomography (CT) revealed a subsolid nodule with a maximal diameter of 20 mm in the left upper lobe (Figure 1). The displaced B¹⁺² ascending behind the left main pulmonary artery and an accessory fissure were also found. Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) revealed a weak uptake for the tumor (SUVmax=2.5). Neither lymph node metastasis nor distant metastasis was detected. Although the histologic diagnosis was not confirmed, she was transferred to Yao Municipal Hospital for surgical treatment.

Preoperative analysis of CT findings was performed using three-dimensional reconstruction images. As a result, a left B¹⁺² arose from the left main bronchus and ascended behind the left main pulmonary artery (Figure 2). In addition, an accessory fissure was detected between the apicoposterior segment (S¹⁺²) and anterior segment (S3) with hypoplastic bronchus (B3) arose from the left B4 (Figure 2B). This patient for whom surgical procedure was planned provided written informed consent after fully talking over the risks and benefits with surgeons.

Figure 1: CT-axial view.
A: tumor in the S1+2 (black arrow).
B: white arrow showing the accessory fissure between S1+2 and S3.

Figure 2: Multiplanar reconstruction CT image using a 3-dimensional volume analyzer.
A: displaced B1+2 ascending behind the left main pulmonary artery.
B: relationship between B1+2 and V1+2. T: tumor. *: hypoplastic B3.

Video-assisted thoracic surgical S¹⁺² segmentectomy with lymph node dissection was performed as follows: The S¹⁺² and the S3 was separated by an accessory fissure. Among the major branches of the superior pulmonary vein, the apicoposterior vein (V1+2) was isolated, ligated, and divided. Then, the displaced B¹⁺² ascending behind V1+2 was identified. For a safer approach, we divided the apicoposterior artery (A1+2) directory arose from the left main pulmonary artery (PA) in the same way. Then, the displaced B¹⁺² was dissected free from its surrounding lymphatic tissue. We clamped this bronchus and performed an inflation test to confirm that the tumor was entirely contained within the S¹⁺² segment. After stapling of the B¹⁺², we divided incomplete interlobar fissure (S¹⁺²/S6) with the stapler, and the specimen was removed from the surgical field. The intraoperative lavage cytology of the resection margin (S¹⁺²/S6) was negative. We dissected lymph nodes along with the lymphatic pathway from peribronchial lymph node of B¹⁺² regarding as a part of hilum (#12 and #10) to subaorta (#5). Intraoperative frozen section histology of #12 and #5 lymph nodes was negative. Bronchial stump was negative at permanent section histology. The pathological diagnosis was T1bN0M0 invasive adenocarcinoma with a 19.5 x 11mm invasive cancer area in the 20 x 12 mm tumor. There was no lymphatic or vascular invasion. Her tumor harbored L878R mutation in EGFR.

The postoperative course was uneventful, and the patient was discharged from the hospital 11 days after surgery. She had no postoperative adjuvant therapy and is now well without recurrence for 65 months after surgery. A minimal change in pulmonary function testing before and at 5 years after surgery was observed, with a forced vital capacity (FVC) of 2.33 L and 2.00 L, and a forced expiratory volume in 1 second (FEV1.0) of 1.82 L and1.67 L, respectively.

Discussion

Three major hypotheses concerning the pathogenesis of anomalous bronchial development have been formulated to explain anomalous bronchi: the reduction, migration, and selection theories [2]. The variations in bronchial bifurcation observed in 30 consecutive asymptomatic and healthy patients were reported by Ghaye et al. [2]. Most variations are seen in the right upper lobe as the typical trifurcation of segmental bronchi. On the contrary, a displaced left B¹⁺², the so-called left tracheal bronchus, is rare.

Our report highlights two points. Firstly, precise preoperative anatomic information on the bronchus and lung vessels is essential to prevent unexpected intraoperative complications. According to our search of the literature , only 7 cases of lung cancer associated with a displaced B¹⁺² including the present case have been reported (Table 1) [3-8]. In 6 of the 7 cases, the displaced B¹⁺² was located behind the left pulmonary artery. In 2 previously reported cases, the displaced B¹⁺² was unexpectedly divided by a stapler at the time of interlobar fissure completion. In both cases, the displaced B¹⁺² could be identified preoperatively, but the comprehensive positional relationship between the displaced B¹⁺² and left main pulmonary artery was nor clarified. In our case, the use of multiplanar reconstruction CT with a 3-dimensional volume analyzer made it possible to clearly depict the displaced B¹⁺² that originated behind the left main pulmonary artery.

Secondly, there has been no report concerning the oncological outcomes after segmentectomy for patients with invasive adenocarcinoma in the isolated left S¹⁺². Sienel et al. advised against the segmentectomy of stage 1A non-small cell lung cancer (NSCLC) in the S1-3 region because of a higher local recurrence rate (23%) [9]. On the other hand, Soukiasian et al. reported that video-assisted thoracoscopic trisegmentectomy is associated with a similar survival rate to lobectomy for stage IA and IB lung cancer. According to a recent report by Altorki et al., sublobar resection and lobectomy are associated with equivalent survival rates for patients with clinical stage IA NSCLC showing solid nodules [10, 11]. Lymphatic invasion is associated with a significantly poorer overall survival in pathological node-negative T1a NSCLC (TNM 7th edition) [12]. When we consider the lymph’s centripetal transport and pathway along with this unique anomalous bronchus, anatomical S¹⁺² segmentectomy with regional lymph node dissection seems to be an acceptable technique with curative intent for the present case. To date, segmentectomy has been performed for only two patients with adenocarcinoma with the same anomaly (Table 1). One of them underwent S¹⁺² segmentectomy because of advanced age [4]. Another underwent tri-segmentectomy of left S¹⁺² and S6 because of severe incomplete lobulation [8]. However, according to our knowledge, there has been no report of a case with long-term follow up longer than 5 years except our report.

We previously reported our rationale of surgical treatment for c-T1aN0M0 (TNM 7th edition) lesions. Basically, we employ standard lobectomy in patients with 16-20mm diameter and < 50% GGO lesion on HRCT [13]. However, this patient is an exceptional case with bronchial anomaly and accessory fissure. As this patient had incomplete interlobar fissure between S¹⁺² and S6 segment, we carefully made the interlobar line with the stapler and confirmed to be cancer-free at intraoperative resection margin cytology [14].

In conclusion, we successfully performed left S¹⁺² segmentectomy for a patient with stage 1A invasive adenocarcinoma entirely contained in the S¹⁺² with a displaced left B¹⁺² and accessory fissure between S¹⁺² and S3. Personalized surgery should be planned based on precise information from preoperative multiplanar reconstruction CT imaging with a 3-dimensional volume analyzer when a trachea-bronchial anomaly is suspected on a routine CT scan.

Table 1: Reported cases of lung cancer associated with displaced B¹⁺²

Author (Year)	Age/Sex	Procedure	Preoperative recognition of displaced Br	Position of displaced Br	Unexpected cutting of Br	Histology	p-stageT1bN0	Survival (Months)
Motohashi (1995)	52/F	LP	+	ND	­	Squamous	T2N1M1	10
Shimamoto (2008)	81/F	S1+2	+	Behind LMPA	+	Adenoca.	T1bN0M0	10
Tsukioka (2011)	62/F	LUL	+	Behind LMPA	+	Adenoca.	T1bN0M0	ND
Asakura (2013)	52/M	LUL	+	Behind LMPA	­	Adenoca.	T2aN0M0	12
Ikuta (2013)	83/M	LUL	+	Behind LMPA	­	Squamous	T2aN0M0	ND
Nakamura (2017)	66/F	S1+2+S6	­	Behind LMPA	­	Adenoca	T2aN0M0	ND
Yamato（2018）	62/F	S1+2	+	Behind LMPA	­	Adenoca.	T1aN0M0	65
Br: bronchus; LP: left pneumonectomy; ND: not described; S1+2: S1+2 segmentectomy; S1+2+S6: S1+2+S6 trisegmentectomy;
LMPA: left main pulmonary artery; LUL: left upper lobectomy

Consent

Written informed consent was obtained from the patient for the publication of this case report and any accompanying images.

Conflict of interest

All authors declare that they have no conflict of interest.

Article Info

Article Type

Case Report

Article History

Received 17 November, 2018
Accepted 20 December, 2018
Published 28 December, 2018

Copyright

© 2018 This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Hosting by Science Repository.
10.31487/j.SCR.2018.03.022

Author Info

Corresponding author

Ken Kodama
Department of Thoracic Surgery, Yao Municipal Hospital, 1-3-1 Ryuge-cho, Yao City, Osaka 581-0069, Japan.

Figures & Tables

Figure 1: CT-axial view.
A: tumor in the S1+2 (black arrow).
B: white arrow showing the accessory fissure between S1+2 and S3.

Figure 2: Multiplanar reconstruction CT image using a 3-dimensional volume analyzer.
A: displaced B1+2 ascending behind the left main pulmonary artery.
B: relationship between B1+2 and V1+2. T: tumor. *: hypoplastic B3.

Table 1: Reported cases of lung cancer associated with displaced B¹⁺²

Author (Year)	Age/Sex	Procedure	Preoperative recognition of displaced Br	Position of displaced Br	Unexpected cutting of Br	Histology	p-stageT1bN0	Survival (Months)
Motohashi (1995)	52/F	LP	+	ND	­	Squamous	T2N1M1	10
Shimamoto (2008)	81/F	S1+2	+	Behind LMPA	+	Adenoca.	T1bN0M0	10
Tsukioka (2011)	62/F	LUL	+	Behind LMPA	+	Adenoca.	T1bN0M0	ND
Asakura (2013)	52/M	LUL	+	Behind LMPA	­	Adenoca.	T2aN0M0	12
Ikuta (2013)	83/M	LUL	+	Behind LMPA	­	Squamous	T2aN0M0	ND
Nakamura (2017)	66/F	S1+2+S6	­	Behind LMPA	­	Adenoca	T2aN0M0	ND
Yamato（2018）	62/F	S1+2	+	Behind LMPA	­	Adenoca.	T1aN0M0	65
Br: bronchus; LP: left pneumonectomy; ND: not described; S1+2: S1+2 segmentectomy; S1+2+S6: S1+2+S6 trisegmentectomy;
LMPA: left main pulmonary artery; LUL: left upper lobectomy

References

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