Long-term outcomes of single-incision laparoscopic colectomy for right-sided colon cancer utilising a craniocaudal approach.

INTRODUCTION: This study aimed to evaluate the short- and long-term outcomes of single-incision laparoscopic colectomy (SILC) for right-sided colon cancer (CC) using a craniocaudal approach. PATIENTS AND METHODS: The data of patients who underwent SILC for right-sided CC at our hospital between January 2013 and December 2022 were retrospectively collected. Surgery was performed using a craniocaudal approach. Short- and long-term operative outcomes were analysed. RESULTS: In total, 269 patients (127 men, 142 women; median age 74 years) underwent SILC for right-sided CC. The cases included ileocaecal resection (n = 138) and right hemicolectomy (n = 131). The median operative time was 154 min, and the median operative blood loss was 0 ml. Twenty-seven cases (10.0%) required an additional laparoscopic trocar, and 9 (3.3%) were converted to open surgery. The Clavien-Dindo classification Grade III post-operative complications were detected in 7 (2.6%) cases. SILC was performed by 25 surgeons, including inexperienced surgeons, with a median age of 34 years. The 5-year cancer-specific survival (CSS) was 96.1% (95% confidence interval [CI] 91.3%-98.2%), and CSS per pathological disease stage was 100% for Stages 0-I and II and 86.2% (95% CI 71.3%-93.7%) for Stage III. The 5-year recurrence-free survival (RFS) was 90.6% (95% CI 85.7%-93.9%), and RFS per pathological disease stage was 100% for Stage 0-I, 91.7% (95% CI 80.5%-96.6%) for Stage II and 76.1% (95% CI 63.0%-85.1%) for Stage III. CONCLUSIONS: SILC for right-sided CC can be safely performed with a craniocaudal approach, with reasonable short- and long-term outcomes.

Effects of obesity on CC16 and their potential role in overweight/obese asthma.

INTRODUCTION: Club cell secretory protein-16 (CC16) is a major anti-inflammatory protein expressed in the airway; however, the potential role of CC16 on overweight/obese asthma has not been assessed. In this study, we examined whether obesity reduces airway/circulatory CC16 levels using experimental and epidemiological studies. Then, we explored the mediatory role of CC16 in the relationship of overweight/obesity with clinical asthma measures. METHODS: Circulating CC16 levels were assessed by ELISA in three independent human populations, including two groups of healthy and general populations and asthma patients. The percentage of cells expressing club markers in obese vs. non-obese mice and human airways was determined by immunohistochemistry. A causal mediation analysis was conducted to determine whether circulatory CC16 acted as a mediator between overweight/obesity and clinical asthma measures. RESULTS: BMI was significantly and monotonously associated with reduced circulating CC16 levels in all populations. The percentage of CC16-expressing cells was reduced in the small airways of both mice and humans with obesity. Finally, mediation analysis revealed significant contributions of circulatory CC16 in the association between BMI and clinical asthma measures; 21.8% of its total effect in BMI's association with airway hyperresponsiveness of healthy subjects (p = 0.09), 26.4% with asthma severity (p = 0.030), and 23% with the required dose of inhaled corticosteroid (p = 0.042). In logistic regression analysis, 1-SD decrease in serum CC16 levels of asthma patients was associated with 87% increased odds for high dose ICS requirement (p < 0.001). CONCLUSIONS: We demonstrate that airway/circulating CC16, which is inversely associated with BMI, may mediate development and severity in overweight/obese asthma.

A novel approach for the complete extraction of large tumours in video-assisted thoracoscopic surgery.

BACKGROUND: Video-assisted thoracoscopic (VATS) lobectomy has recently become the standard for treating lung cancer. However, the complete removal of large tumours from the chest cavity is often difficult. Therefore, we developed a novel approach to extract large tumours from the wound without rib resection or fracture (the eXtraction of resected specimens through the Lower INterCostal route [XLINC] method). SUBJECTS AND METHODS: In XLINC, a skin incision is made on the tenth intercostal space, and the resected lung tissue is extracted. This retrospective study included patients who underwent VATS lobectomy using XLINC in our institution from 2016 to 2018. As a control group, six patients who had undergone thoracotomy during VATS surgery due to a large tumour diameter were included in the conversion group. RESULTS: Four men and six women (median age = 66 years, maximum median tumour diameter = 59 mm) were included in the study. The median length of the wound incision for XLINC was 4.5 (range: 4-8) cm. The median operative time was 183 min, and the estimated blood loss was 50 ml. Rib resection was not required, and no fractures were noted. The median length of hospital stay was 8 days. No patients developed major complications caused by XLINC. There were no significant differences, except in operation time and amount of blood loss, between the two groups. However, the XLINC group used fewer post-operative analgesics. CONCLUSION: Our report suggests that XLINC might be a simpler, less invasive procedure that could be used in patients with large tumours.

Left upper lobectomy is a risk factor for cerebral infarction after pulmonary resection: a multicentre, retrospective, case-control study in Japan.

PURPOSE: The anatomical site of resected lobes may influence postoperative cerebral infarction. The objective of the current study was to determine if left upper pulmonary lobectomy is a risk factor for postoperative cerebral infarction. METHODS: This was a retrospective case-control study in patients undergoing pulmonary lobectomy from 2004 to 2013 in Japan. We retrospectively identified 610 patients from 153 institutions who had developed postoperative cerebral infarction following pulmonary lobectomy. The control group consisted of 773 patients who underwent lobectomy without cerebral infarction during a randomly selected single month in 2009 at the same institutions. RESULTS: Factors associated with cerebral infarction were age [10-year intervals, odds ratio (OR): 1.46; 95% confidence interval (CI): 1.23-1.73; p < 0.001], male sex (OR 1.92; 95% CI 1.29-2.86; p = 0.001), presence of comorbidities (OR 1.82; 95% CI 1.35-2.44; p < 0.001), perioperative anti-platelet or anti-coagulant drug use (OR 1.71; 95% CI 1.20-2.45; p = 0.003), and lobectomy. Subgroup analyses revealed that cerebral infarction was strongly associated with left upper lobectomy. CONCLUSIONS: Our findings suggest that left upper lobectomy is associated with a higher risk of cerebral infarction than other types of lobectomy, particularly in the early postoperative period.

Correction to: Left upper lobectomy is a risk factor for cerebral infarction after pulmonary resection: a multicentre, retrospective, case-control study in Japan.

The original article can be found online.

[Bronchial Stump Coverage Technique by da Vinci Xi].

da Vinci's greatest attractions are the fine images acquired with a high-resolution 3-dimensional( 3D) endoscope and the precise operation by forceps equipped with an articulated arm. We believed that complicated procedures can benefit from robot-assisted surgery. We have been actively performing collection and sewing of viable tissue using da Vinci Xi for the purpose of preventing bronchial stump fistulas. Of the 44 cases of lobectomy performed by the end of November 2019 using da Vinci Xi, 13 cases underwent bronchial stump covering. The covering procedure was intended for patients with conditions such as diabetes and a history of internal use of steroids. As the dressing, pedicled intercostal muscle was used in 4 cases, and free pericardial fat tissue was used in 9 cases. A good visual field was obtained by appropriately turning the oblique mirror upside down. The smoke emission effect of AirSeal was useful for securing the visual field. The dressing was sutured and fixed using 3-0 or 4-0 Prolene( SH) cut to a length of 10 to 12 cm. The postoperative course was good and bronchial stump fistula did not occur in all cases.

Clinical Course of Histologically Proven Multifocal Micronodular Pneumocyte Hyperplasia in Tuberous Sclerosis Complex: A Case Series and Comparison with Lymphangiomyomatosis.

BACKGROUND: Multifocal micronodular pneumocyte hyperplasia (MMPH) is a rare pulmonary manifestation of tuberous sclerosis complex (TSC). Because of its rarity, no previous study has described the detailed clinical course of this disease. OBJECTIVES: This study aimed to clarify the longitudinal clinical characteristics of subjects with MMPH. METHODS: Nine patients with MMPH diagnosed at Hokkaido University Hospital were retrospectively analyzed. Changes in computed tomography findings and pulmonary function were compared during the follow-up period. Serum levels of KL-6, surfactant protein (SP)-A, and SP-D were measured to clarify their potentials as blood biomarkers of the disease. Fourteen cases of lymphangiomyomatosis (LAM) were also included to compare their clinical characteristics with those of subjects with MMPH. RESULTS: Of the 9 patients, 7 were female and 2 were male. The median age at diagnosis was 43 years (range, 19-56), and all cases were diagnosed following incidental abnormal radiographic findings. During the follow-up, 1 patient died of lung cancer, but others were radiographically stable and had stable pulmonary function. Serum levels of SP-A in 5 patients (mean, 146.4 ng/mL) and SP-D in 6 patients (mean, 337.3 ng/mL) were elevated in subjects with MMPH, whereas KL-6 levels were within the reference range (mean, 230 U/mL) in all patients. Levels of SP-A and SP-D were significantly higher in subjects with MMPH than those with LAM (p < 0.05). CONCLUSIONS: Radiographic findings and pulmonary function were stable in all cases of MMPH. Serum SP-A and SP-D, but not KL-6, may be useful markers for suspicion of the presence of MMPH in patients with TSC.

Expression of fucosyltransferase 8 is associated with an unfavorable clinical outcome in non-small cell lung cancers.

UNLABELLED: Objecitive: Fucosyltransferase 8 (FUT8), the only enzyme responsible for the core α1,6-fucosylation of asparagine-linked oligosaccharides of glycoproteins, is a vital enzyme in cancer development and progression. We examined FUT8 expression in non-small cell lung cancers (NSCLCs) to analyze its clinical significance. We also examined the expression of guanosine diphosphate-mannose-4,6-dehydratase (GMD), which is imperative for the synthesis of fucosylated oligosaccharides. METHODS: Using immunohistochemistry, we evaluated the expression of FUT8 and GMD in relation to patient survival and prognosis in potentially curatively resected NSCLCs. RESULTS: High expression of FUT8 was found in 67 of 129 NSCLCs (51.9%) and was significantly found in non-squamous cell carcinomas (p = 0.008). High expression of FUT8 was associated with poor survival (p = 0.03) and was also a significant and independent unfavorable prognostic factor in patients with potentially curatively resected NSCLCs (p = 0.047). High expression of GMD was significantly associated with high FUT8 expression (p = 0.04). CONCLUSIONS: High expression of FUT8 is associated with an unfavorable clinical outcome in patients with potentially curatively resected NSCLCs, suggesting that FUT8 can be a prognostic factor. The analysis of FUT8 expression and its core fucosylated products may provide new insights for the therapeutic targets of NSCLCs.

[The significance of metastasectomy in patients with metastatic renal cell carcinoma].

We conducted a retrospective study to clarify the clinical significance of metastasectomy in patients with metastatic renal cell carcinoma (mRCC). Of 83 mRCC patients who were treated at our hospital between 2005 and 2010, 19 patients who underwent metastasectomy during the treatment course were the subjects of the present study. By the purpose and timing of metastasectomy, we classified the 19 patients into three groups : (1) patients who immediately underwent metastasectomy at diagnosis of metastasis (primary group), (2) patients who underwent resection of clinically problematic metastatic lesions for the relief of their symptoms (palliative group), and (3) patients who underwent complete resection of all metastatic lesions after sufficient systemic therapies (consolidation group). In the primary group (n=5), four patients had lung metastasis and one had metastases to limbs and the adrenal gland. Overall survival at 3 years was 100%. In the palliative group (n=4), 3 patients underwent resection of brain metastasis and one underwent resection of skin metastasis. The symptoms associated with metastasis clearly improved. In the consolidation group (n=10), the metastasized organ was the lung in 5 patients, pancreas in 4, and liver in one. Preoperative systemic therapy included sunitinib or sorafenib in 5 patients, interferon-α in 4, and S-1 in one. After metastasectomy, systemic therapies were discontinued in 9 patients, 4 of whom did not experience RCC recurrence, with a median follow-up of 35 months. Overall survival at 3 years was 60%. Metastasectomy would be a good treatment option in patients with mRCC.

[Mediastinal Mature Teratoma Necessitating Resection of Superior Vena Cava].

A 43-year-old woman was referred to our hospital for an abnormal shadow on chest X-ray. Computed tomography revealed a tumor with calcification of 9.8 cm in size at the anterior mediastinum. The infiltration into the left brachiocephalic vein and superior vena cava by tumor was suspected. Surgery was performed under a diagnosis of mature teratoma. The tumor was found to adhere firmly to superior vena cava (SVC), left brachiocephalic vein, right phrenic nerve, and the arch of the azygos vein. To ensure the blood flow, an artificial blood vessel was placed between left brachiocephalic vein and right atrium. Then SVC was clamped and the tumor was resected with the part of SVC.

[Investigation of lung cancer patients with cardiovascular disease].

BACKGROUND: According to the aging in Japan, surgery of lung cancer with cardiovascular disease is increasing. Among them, the merger of the heart and large blood vessel disease would be expected to be directly linked to the perioperative management. MATERIALS AND METHODS: We conducted a retrospective analysis of 1,005 patients who had undergone surgical resection of primary lung adenocarcinoma between January 1997 and June 2014 at Hokkaido University Hospital. Among them, 81 patients had more than one cardiovascular disease. RESULTS: The median age was 71 years old. Men are 62 cases(76%). 64 cases (79%)had smoking history. Ischemic heart disease( IHD) was 29 cases(33%), followed by atrial fibrillation(Af), arrhythmia other than Af, valve disease and macrovascular disease. Anticoagulant or antiplatelet therapy were preoperatively done in 41% of IHD cases, 39% of Af cases. Thirty four% of IHD, 50% of vascular disease received the treatment other than medication. Video-assisted thoracic surgery was performed in 67 cases(83%). Lobectomy, sublobectomy were performed for 59 cases(73%), 19 cases(23%), respectively. Postoperative complications were occurred in 32 cases(40%). Two patients(2.5%)died in hospital without discharge. Univariate analysis revealed tumor size, pStage, lymph node dissection, operation time or blood loss were correlated with postoperative complication. CONCLUSIONS: For the patients with cardiovascular disease, careful evaluation of surgical indication, perioperative management is required.

A simple and safe surgical technique for nonpalpable lung tumors: One-stop Solution for a nonpalpable lung tumor, Marking, Resection, and Confirmation of the surgical margin in a Hybrid operating room (OS-MRCH).

When performing thoracoscopic partial resections of nonpalpable lung tumors such as ground-glass opacities (GGOs) and small tumors, detecting the location of the lesion and assessing the resection margins can be challenging. We have developed a novel method to ease this difficulty, the One-stop Solution for a nonpalpable lung tumor, Marking, Resection, and Confirmation of the surgical margin in a Hybrid operating room (OS-MRCH), which uses a hybrid operating room wherein the operating table is seamlessly integrated with cone-beam computed tomography (CBCT). We performed the OS-MRCH method on 62 nodules including primary lung cancer presenting with GGO. Identification of the lesion and confirmation of the margin were performed in 58 of the cases, while nodules were detected in all. The frequency of computed tomography (CT) scans performed prior to resection was one time in 51 cases, two times in eight cases, and ≥3 times in three cases. Additional resection was performed in two cases. The median operative time was 85.0 minutes, and the median pathological margin was 11.0 mm. The key advantages of this method are that all surgical processes can be completed in a single session, specialized skill sets are not required, and it is feasible to perform in any facility equipped with a hybrid operating room. To overcome its disadvantages, such as longer operating time and limited patient positioning, we devised various methods for positioning patients and for CT imaging of the resected specimens. OS-MRCH is a simple, useful, and practical method for performing thoracoscopic partial resection of nonpalpable lung tumors.

Developing a Virtual Reality Simulation System for Preoperative Planning of Robotic-Assisted Thoracic Surgery.

Background. Robotic-assisted thoracic surgery (RATS) is now standard for lung cancer treatment, offering advantages over traditional methods. However, RATS's minimally invasive approach poses challenges like limited visibility and tactile feedback, affecting surgeons' navigation through com-plex anatomy. To enhance preoperative familiarization with patient-specific anatomy, we devel-oped a virtual reality (VR) surgical navigation system. Using head-mounted displays (HMDs), this system provides a comprehensive, interactive view of the patient's anatomy pre-surgery, aiming to improve preoperative simulation and intraoperative navigation. Methods. We integrated 3D data from preoperative CT scans into Perspectus VR Education software, displayed via HMDs for in-teractive 3D reconstruction of pulmonary structures. This detailed visualization aids in tailored preoperative resection simulations. During RATS, surgeons access these 3D images through Tile-ProTM multi-display for real-time guidance. Results. The VR system enabled precise visualization of pulmonary structures and lesion relations, enhancing surgical safety and accuracy. The HMDs offered true 3D interaction with patient data, facilitating surgical planning. Conclusions. VR sim-ulation with HMDs, akin to a robotic 3D viewer, offers a novel approach to developing robotic surgical skills. Integrated with routine imaging, it improves preoperative planning, safety, and accuracy of anatomical resections. This technology particularly aids in lesion identification in RATS, optimizing surgical outcomes.

Bronchiolar epithelial catalase is diminished in smokers with mild COPD.

This study aimed to investigate bronchiolar catalase expression and its relationship with smoking and/or chronic obstructive pulmonary disease (COPD) in humans and to determine the dynamic change of bronchiolar catalase expression in response to cigarette smoke in mice. Lung tissue was obtained from 36 subjects undergoing surgery for peripheral tumours, consisting of life-long nonsmokers and smokers with or without COPD. Male C57BL/6 mice were subjected to cigarette smoke exposure for up to 3 months followed by a 28-day cessation period. We quantified bronchiolar catalase mRNA using laser capture microdissection and quantitative reverse transcription-polymerase chain reaction. C22 club cells (Clara cells) in culture were exposed to cigarette smoke extract and monitored for viability when catalase expression was decreased by siRNA. Catalase was decreased at mRNA and protein levels in bronchiolar epithelium in smokers with COPD. In mice, bronchiolar catalase is temporarily upregulated at 1 day after cigarette smoke exposure but is downregulated by repeated cigarette smoke exposure, and is not restored long after withdrawal once emphysema is developed. Decreasing catalase expression in C22 cells resulted in greater cigarette smoke extract-induced cell death. Bronchiolar catalase reduction is associated with COPD. Regulation of catalase depends on the duration of cigarette smoke exposure, and plays a critical role for protection against cigarette smoke-induced cell damage.

Histopathologic characterization of lung adenocarcinoma in relation to fluorine-18-fluorodeoxyglucose uptake on positron emission tomography.

BACKGROUND: Fluorine-18-fluorodeoxyglucose uptake on positron emission tomography is reported to have prognostic significance in patients after resection of lung adenocarcinoma. However, its relationship with histopathologic features remains unknown. METHODS: We conducted a retrospective analysis of 205 patients who had undergone surgical resection of primary lung adenocarcinoma (> 1.0 cm) after preoperative fluorine-18-fluorodeoxyglucose-positron emission tomography between January 1999 and December 2008 at Hokkaido University Hospital. Fluorine-18-fluorodeoxyglucose uptake was measured by the maximum standardized uptake value. A histopathologic review was performed according to the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification, and various histopathologic factors were evaluated semi-quantitatively. Correlations between these clinicopathologic factors and the maximum standardized uptake value (high ≥ 2.0 vs low < 2.0) were analyzed. RESULTS: Univariate analysis of clinicopathologic factors demonstrated that the following were significantly correlated with a high maximum standardized uptake value: an elevated carcinoembryonic antigen level, larger tumor size, upgraded pT, pN, pStage, non-lepidic histology, abundant fibroblastic/hyalinized stroma, necrosis, presence of pleural involvement, lymphatic and vascular invasion and more intra- and extracellular mucin. Multivariate analysis demonstrated that a tumor size of > 2.0 cm, non-lepidic histology and abundant fibroblastic/hyalinized stroma were significantly correlated with the high maximum standardized uptake value. CONCLUSION: More histopathologic factors are known to correlate with poor prognosis in lung adenocarcinomas showing high maximum standardized uptake values than in those showing low maximum standardized uptake values. Therefore, prognostication of patients with a resectable lung adenocarcinoma on the basis of preoperative fluorine-18-fluorodeoxyglucose uptake is histopathologically valid. Such observations may also help us to clarify the pathobiological mechanism responsible for the increased fluorine-18-fluorodeoxyglucose uptake in lung adenocarcinomas with a poor prognosis.

A novel edge-marking method in pleural covering with video-assisted thoracic surgery.

Total pleural covering is implemented to reinforce the visceral pleura with surgical sheets. It has been adopted for diffuse cystic lung diseases such as lymphangioleiomyomatosis to prevent pneumothorax and has achieved good results. The procedure is technically demanding, because it is difficult to cover the entire visceral pleura without disarrangement and jamming of surgical sheets, especially during thoracoscopic surgery, where grasping of a wrong site might happen when unfolding the sheets. Herein, we report a technique to cover the entire pleura with dotted line folded sheets to ease the thoracoscopic procedure. We found that the use of this marking method made the procedure easier, with just a little ingenuity, because marking the edges of sheets with dashed lines clarifies the site that should be grasped, thus preventing the incidence of grasping the wrong part of the sheet. Pleural covering with dotted line folded surgical sheets is a useful method for reduced port thoracoscopic surgery.

Tumor-to-thoracic height ratio as an easy method to predict the feasibility of reduced-port video-assisted thoracic surgery for mediastinal lesions in children: a single-center experience.

In the last few decades, reduced-port video-assisted thoracic surgery (RP-VATS) has been developed to minimize surgical invasiveness. Nevertheless, VATS in children can occasionally be difficult because the lesion occupies a small thoracic cavity, limiting the working space. This study aimed to assess the feasibility of RP-VATS for the resection of mediastinal lesions in children in association with the tumor-to-thoracic height ratio (TTH ratio). We reviewed all patients aged ≤10 years who underwent resection for mediastinal lesions in our institute between January 2008 and August 2022. Patients who underwent diagnostic procedures were excluded from this study. The TTH ratio was calculated as tumor height divided by thoracic height. Seven patients in the RP-VATS group and six in the conventional procedures (multi-portal VATS or open surgery) group were included in this study. The TTH ratio was significantly lower in the RP-VATS group than in the conventional procedures group (median, 26.3% vs. 50.8%; P=0.007). The operating time (P=0.01) and duration of drainage (P=0.003) were significantly shorter and the blood loss (P=0.001) was significantly lower in the RP-VATS group than in the conventional procedures group. After adjusting for age, a lower TTH ratio was significantly associated with the completion of RP-VATS (odds ratio: 0.776; 95% confidence interval: 0.529-0.926; P=0.048). In conclusion, RP-VATS can be performed appropriately in carefully selected cases of pediatric mediastinal lesions. A low TTH ratio may predict the feasibility of RP-VATS. Further studies are warranted to determine the criteria for the indications of RP-VATS in children, so that more children can benefit from RP-VATS.

High density and proximity of CD8+ T cells to tumor cells are correlated with better response to nivolumab treatment in metastatic pleural mesothelioma.

BACKGROUND: The efficacy of immune checkpoint inhibitors (ICIs) in pleural mesothelioma has recently been established. The response to ICIs can be predicted by quantitative analysis of cells and their spatial distribution in the tumor microenvironment (TME). However, the detailed composition of the TME in pleural mesothelioma has not been reported. We evaluated the association between the TME and response to ICIs in this cancer. METHODS: A retrospective analysis of 22 pleural mesothelioma patients treated with nivolumab in different centers was performed using surgical specimens. Four patients had a partial response to nivolumab (response group) and 18 patients had stable or progressive disease (nonresponse group). The number of CD4, CD8, FoxP3, CK, and PD-L1 positive cells, cell density, and cell-to-cell distance were analyzed by multiplex immunofluorescence. RESULTS: PD-L1 expression did not differ significantly between the response and nonresponse groups. The density of total T cells and of CD8+ T cells was significantly higher in the response than in the nonresponse group. CD8+ T cells were more clustered and located closer to tumor cells, whereas regulatory T cells were located further from tumor cells in the response than in the nonresponse group. CONCLUSIONS: High density and spatial proximity of CD8+ T cells to tumor cells were associated with better response to nivolumab, whereas the proximity of regulatory T cells to tumor cells was associated with worse response, suggesting that the distinct landscape of the TME could be a potential predictor of ICI efficacy in pleural mesothelioma.

[Indication of video-assisted thoracic surgery for mediastinal mass lesions].

BACKGROUND: Most of mediastinal tumors are benign cysts and neoplasms. Resection is indicated for cystic lesions because of possibility of malignancy, compression symptom and possible rupture in future. However careful observation might be appropriate for asymptomatic tumors without risk of malignancy. Although video-assisted thoracoscopic surgery (VATS) is increasingly performed, its indication is still controversial. PATIENTS AND RESULTS: Among 37 mediastinal cystic lesions with confirmed pathological diagnosis, 17 were neoplasms. All of 20 non-neoplastic lesions have cyst wall thinner than 5 mm. Five cases( 29%) of neoplastic lesions have cyst wall thinner than 5 mm. Three of them underwent preoperative fluorodeoxyglucose-positron emission tomography( FDG-PET) or PET-computed tomography( CT). All 3 neoplastic lesions with thin wall showed accumulation of FDG. None of non-neoplastic cyst had FDG accumulation. Ninety-seven patients underwent surgical resection for mediastinal tumors. Out of 51 VATS, 2 were converted to open thoracotomy. One patient with thymoma had ipsilateral pleural recurrence after VATS. Tumor sizes of those 3 patients were larger than 7 cm. CONCLUSIONS: Cystic mediastinal tumor with wall thickness less than 5 mm and no FDG accumulation might be observed without resection because it is very unlikely to be a neoplasm. Mediastinal tumor larger than 7 cm might not be suitable for VATS.