Bronchial branching patterns and volumetry in the right upper lobe: impact on segmentectomy planning.

OBJECTIVES: The use of segmentectomy is expected to increase. However, understanding of the segmental bronchial branching is limited. Herein, we aimed to investigate bronchial branching pattern complexity and segmental volumetry of the right upper lung lobe to develop an accurate understanding of segmental anatomy and contribute to the advancement of safe and efficient lung segmentectomy. METHODS: We evaluated chest computed tomography scans of 303 patients and categorized the branching of segmental bronchi (segment 1, apical; segment 2, posterior; and segment 3, anterior) into 4 major types (typical trifurcated, bifurcated non-defective, bifurcated defective and atypical trifurcated) and 11 subtypes. Segmental volumetry was performed to determine the predominant segment in each case (volume difference <5% was considered equal). Branching complexity was evaluated separately for volumetry-predominant and volumetry-non-predominant segments. RESULTS: Trifurcated non-defective was the most frequent branching type (64.4%), followed by bifurcated non-defective (22.1%), bifurcated defective (8.6%) and trifurcated half-defective (4.0%). In terms of segmental volumetry, most cases had a one-segment-predominant distribution (71%) and only 5% of cases had equal distribution (segment 1 = segment 2 = segment 3). More than half of the cases had a segment 3-predominant distribution (52%). Branching complexity analysis revealed that the volumetry-non-predominant segment was associated with a higher risk of complex branching patterns compared with the volumetry-predominant segment (37% vs 19%, respectively; P < 0.005). CONCLUSIONS: Volumetric assessment of the right upper lobe showed a heterogeneous segmental volume distribution. Care should be taken during lung segmentectomy of the volumetry-non-predominant segments because of the high risk associated with complex bronchial branching patterns. CLINICAL TRIAL REGISTRATION: No. 4840.

Significance of the evaluation of tracheal length using a three-dimensional imaging workstation.

Background: Limited information is available on the total tracheal length and its other characteristics for tracheal surgery. This study aimed to investigate the reference value of tracheal length and assess its relationship with physiological variables. Methods: We measured the tracheal length of 215 patients (107 men and 108 women) who underwent contrast-enhanced computed tomography before thoracic surgery using a three-dimensional imaging workstation. Pearson correlation analysis and multiple linear regression analysis were performed to investigate the relationship between the total tracheal length (cervical and thoracic) and common physiological parameters. Results: The mean total tracheal length was 11.5±1 cm (range, 8.8-14.4 cm); 8% of the patients had a total tracheal length <10 cm. The cervical trachea was significantly shorter in men than in women (2.9±1.3 vs. 3.8±1.3 cm, P<0.001), whereas the thoracic trachea was significantly longer in men than in women (8.9±1.1 vs. 7.4±1.1 cm, P<0.001). Correlation analysis showed that the total tracheal length was positively associated with height in both sexes, while the height was positively associated with only cervical tracheal length. In the multiple linear regression analysis, the total tracheal length was influenced most by height, while cervical and thoracic tracheal lengths were influenced most by sex. Older age was also an independent contributor to a shorter cervical trachea and longer thoracic trachea in both sexes. Conclusions: The total tracheal length ranged from short to long in individuals, and characteristics of tracheal length varied with height, age, sex, and part of the trachea. We should thus be aware of the tracheal length of each patient for appropriate tracheal management.

Is using a consolidation tumor ratio 0.5 as criterion feasible in daily practice? Evaluation of interobserver measurement variability of consolidation tumor ratio of lung cancer less than 3 cm in size.

BACKGROUND: Consolidation tumor ratio (CTR) calculated as the ratio of the tumor consolidation diameter to the tumor maximum diameter on thin-section computed tomography (CT) of lung cancer has been reported as an important prognostic factor. It has also been used for treatment decision-making. This study aimed to investigate the interobserver variability of CTR measurements on preoperative CT and propose a clinically useful CTR-based classification criterion. METHODS: We enrolled 119 patients who underwent surgery for suspected or diagnosed small-sized lung cancer (≤3.0 cm in diameter). Nine doctors reviewed preoperative CT scans to measure CTR. Interobserver variability of CTR measurements was evaluated using the coefficient of variation (CV) and Fleiss' κ. The prognostic effect of the CTR-based classification was assessed using the Kaplan-Meier method. RESULTS: Interobserver variability of CTR measurement was the highest for tumors with the lowest CTR (CTR = 0); it decreased as CTR increased and reached a plateaued level of low variability (CV <0.5) at CTR of 0.5. We proposed a three-group classification based on the findings of CTR interobserver variability (CTR < 0.5, 0.5 ≤ CTR < 1, and CTR = 1). Interobserver agreement of the judgment of the CTR-based classification was excellent (Fleiss' κ = 0.81). The classification significantly stratified patient prognosis (p < 0.001, 5-year overall survival rates with CTR < 0.5, 0.5 ≤ CTR < 1, and CTR = 1 were 100, 88, and 73.8%, respectively). CONCLUSIONS: CTR 0.5 is a clinically relevant and helpful cutoff for treatment decision-making in patients with early-stage lung cancer based on high interobserver agreement and good prognostic stratification.

Epidemiological analysis of lung and mediastinal neuroendocrine neoplasms in Japan based on the national database.

BACKGROUND: Neuroendocrine neoplasms (NENs) are rare and can originate from any body part. However, there are only few epidemiological studies, especially on lung and mediastinal NENs. This study investigated the epidemiological trends and differences between lung and mediastinal NENs in Japan. METHODS: Patients with lung and mediastinal NENs were identified in a national hospital-based cancer registry between 2009 and 2015 in Japan. NENs were subclassified into neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs). NECs were further subdivided into large neuroendocrine carcinomas (LCNECs) and small cell carcinomas (SCCs). We examined the patient characteristics: sex, age, histology, year of diagnosis, diagnostic opportunity, and initial treatment. RESULTS: We identified 48,433 patients with 47,888 lung (98.9%) and 545 mediastinal (1.1%) NENs. The commonest subtype of lung NENs was SCCs (87%), followed by LCNECs (10%) and NETs (3%). In the mediastinum, SCCs were also the commonest (48%), followed by NETs (38%) and LCNECs (14%). The number of lung NEN annually increased; however, that of mediastinal NENs did not change over time. The mean age of patients with lung NETs was lower than that of patients with lung LCNECs and SCCs (NETs, 62 ± 14 years; LCNECs, 70 ± 9 years; SCCs, 71 ± 9 years; p < .001). The lung and mediastinal NENs were mainly detected based on symptoms, except for lung NETs. Surgical intervention, including multimodal therapy, was performed for 89.3% of lung NETs (surgery alone: 83.6%), while only 15.6% of lung NECs were treated with surgery. For the mediastinum, 75.9% of NETs were treated with surgery, with 27.1% of cases treated with surgery plus multimodal therapy. Surgery was performed more frequently for mediastinal NECs (37%) than for lung NECs (15.6%). CONCLUSIONS: This study highlights differences in trends of lung and mediastinal NENs. This study's findings support the importance of epidemiological evaluations based on the primary sites and histological subtypes.

Prediction of Pulmonary Artery-Adherent Lymph Nodes for Minimally Invasive Lung Resection.

BACKGROUND: During minimally invasive surgery (MIS), pulmonary artery (PA)-adherent lymph nodes (LNs) may increase the risk of conversion to thoracotomy and/or PA injury. The aims of this study were to investigate (1) preoperative workups as predictors of PA-adherent LNs and (2) predictors of conversion/PA injury during MIS. METHODS: We investigated 1210 patients who underwent anatomical lung resection (MIS: 772, thoracotomy: 438) and determined the PA-adherent LN status by reviewing the operation video/record. The size and calcification of the hilar LNs on computed tomography, bilateral high metabolic activity on positron emission tomography, and mucosal dark pigmentation on bronchoscopy were evaluated as potential predictors for PA-adherent LNs. RESULTS: Among patients who underwent all 3 workups (n = 594), both bronchoscopy and computed tomography were independent predictors for PA-adherent LNs; the combination of dark pigmentation and LN size ≥8 mm stratified patients according to the risk of PA-adherent LNs (lowest to highest risk, 3%-65%). Among the patients who underwent MIS (n = 772), conversion and PA injuries were observed in 32 (4%) and 25 (3%) patients, respectively. Multivariate analysis revealed that the presence of PA-adherent LNs was an independent predictor of both conversion and PA injury (both P < .001). The effect of PA-adherent LNs on conversion risk was significantly modified by the resected lobe (P = .008). CONCLUSIONS: The presence of PA-adherent LNs is associated with a high risk of conversion/PA injury during MIS. Bronchial dark pigmentation, size of hilar LNs, and their combination are useful for predicting PA-adherent LNs; this finding may help in achieving safer MIS.

Preemptive Intercostal Nerve Block as an Alternative to Epidural Analgesia.

BACKGROUND: The necessity of thoracic epidural analgesia (TEA) during minimally invasive surgery (MIS) remains unclear. We investigated TEA efficacy in MIS versus thoracotomy and the noninferiority of a preemptive intercostal nerve block (ICNB) to TEA in MIS. METHODS: We investigated 393 patients who underwent lung resection, with and without TEA, between 2014 and 2019 (242 MIS, 151 thoracotomy) and 93 patients who underwent MIS with ICNB between 2019 and 2020. To address selection bias 70 TEA and 70 ICNB patients were propensity score matched. Endpoints were pain score during hospitalization, postoperative complications, duration of operating room use, analgesia-related adverse effects, and use of supplemental pain medication. RESULTS: One-third of patients with MIS discontinued TEA on postoperative day 1 or earlier; those with early TEA discontinuation reported worse pain the next day. TEA was associated with lower pain scores compared with non-TEA, regardless of surgical invasiveness, and a lower complication risk in patients with thoracotomy but not MIS. For MIS, ICNB was associated with an equivalent pain score on postoperative day 1, lower average pain score during hospitalization, shorter duration of operation room use, less frequent use of supplemental pain medication, and similar risk of postoperative complication and analgesia-related adverse effects compared with TEA after matching. CONCLUSIONS: Given early TEA discontinuation after MIS and ICNB's noninferior pain relief, preemptive ICNB can be an alternative for TEA in patients undergoing MIS.

Non-incisional pleurectomy/decortication for malignant mesothelioma after cardiac surgery.

A 70-year-old man diagnosed with right-sided malignant epithelial pleural mesothelioma, underwent pleurectomy/decortication after three courses of neoadjuvant chemotherapy. He had a history of mitral valve replacement and maze procedure with median sternotomy, and the procedures resulted in strong adhesion from the apex to the mediastinal side. In particular, the peeling of the area where the tumor invaded the pericardium required the most attention; however, the involved pericardium could be partially resected without damaging the right atrium. Finally, en bloc macroscopic complete resection with the entire pleura was successfully performed without conversion to extrapleural pneumonectomy.

Impact of counterclockwise rotation of the right middle lobe following right upper lobectomy.

OBJECTIVES: Following right upper lobectomy, the right middle lobe may shift towards the apex and rotate in a counterclockwise direction with respect to the hilum. This study aimed to investigate the incidence and clinical impact of middle lobe rotation in patients undergoing right upper lobectomy. METHODS: From January 2014 to November 2018, 82 patients underwent right upper lobectomy at our institution for lung cancer using a surgical stapler to divide the minor fissure. Postoperative computed tomography scans evaluated the counterclockwise rotation of the middle lobe, in which the staple lines placed on the minor fissure were in contact with the major fissure of the right lower lobe (120° counterclockwise rotation). Clinicoradiological factors were evaluated and compared between patients with and without middle lobe rotation. We also reviewed surgical videos in patients with middle lobe rotation to evaluate the position of the middle lobe at the end of surgery. RESULTS: Nine patients had a middle lobe rotation (11%), where 1 patient required surgical derotation. Patients with middle lobe rotation were significantly associated with more frequent right middle lobe atelectasis and severe postoperative complications compared with those without rotation. A surgical video review detected potential middle lobe rotation at the end of the surgery. CONCLUSIONS: Middle lobe rotation without torsion following right upper lobectomy is not rare, and it is associated with adverse postoperative courses. Careful positioning of the right middle lobe at the end of surgery is warranted to improve postoperative outcomes.

A Novel Strategy for the Diagnosis of Pulmonary High-Grade Neuroendocrine Tumor.

Correctly diagnosing a histologic type of lung cancer is important for selecting the appropriate treatment because the aggressiveness, chemotherapy regimen, surgical approach, and prognosis vary significantly among histologic types. Pulmonary NETs, which are characterized by neuroendocrine morphologies, represent approximately 20% of all lung cancers. In particular, high-grade neuroendocrine tumors (small cell lung cancer and large cell neuroendocrine tumor) are highly proliferative cancers that have a poorer prognosis than other non-small cell lung cancers. The combination of hematoxylin and eosin staining, Ki-67, and immunostaining of classic neuroendocrine markers, such as chromogranin A, CD56, and synaptophysin, are normally used to diagnose high-grade neuroendocrine tumors; however, they are frequently heterogeneous. This article reviews the diagnostic methods of lung cancer diagnosis focused on immunostaining. In particular, we describe the usefulness of immunostaining by Stathmin-1, which is a cytosolic phosphoprotein and a key regulator of cell division due to its microtubule depolymerization in a phosphorylation-dependent manner, for the diagnosis of high-grade neuroendocrine tumors.

Three-dimensional computed tomography-guided excision of an intrathoracic giant thymoma with elongated thymic vessels.

We report the case of an intrathoracic giant thymoma with elongated thymic vessels, which was successfully resected under three-dimensional computed tomography guidance. A large, left-sided intrathoracic mass was incidentally found in a 41-year-old woman during a routine work-up for uterine cancer. Six vessels were noted arising from the tumor, five of which were connected to the anterosuperior mediastinum. The vasculature suggested that the tumor originated from the thymus and grew into the left pleural cavity, which pulled and elongated the associated vessels. Preoperative computed tomography imaging demonstrated that these vessels were located behind the tumor, which increased the risk for catastrophic intraoperative bleeding. We created a detailed surgical plan using our preoperative computed tomography data and successfully excised the tumor using intraoperative three-dimensional computed tomography guidance. Histopathological examination revealed a type AB thymoma without capsular invasion. This case highlighted the role of preoperative planning and intraoperative imaging in resecting an intrathoracic giant thymoma safely. In the video, we demonstrate how we performed the procedure under three-dimensional navigation.

Usefulness of SS18-SSX antibody as a diagnostic marker for pulmonary metastatic synovial sarcoma.

BACKGROUND: The novel SS18-SSX fusion-specific antibody is reported to have high sensitivity and specificity for the diagnosis of primary synovial sarcoma (SS), which often metastasizes to the lung. Thus far, no study has validated the diagnostic efficacy of SS18-SSX antibody for pulmonary metastatic SS. Therefore, we aimed to investigate the usefulness of the SS18-SSX antibody in the diagnosis of pulmonary metastatic SS. METHODS: We evaluated the immunohistochemistry of SS18-SSX fusion-specific antibody (E9X9V) in 10 pulmonary metastatic SS cases and the corresponding five primary sites (four limbs and one mediastinum) in five patients, for whom SS was already diagnosed and confirmed by fluorescence in-situ hybridization in the metastatic and primary sites, and in 93 clinical and histologic mimics including 49 non-SS, pulmonary metastatic sarcomas, 39 primary lung cancers, and five intrathoracic solitary fibrotic tumors. All specimens were surgically resected at Shinshu University Hospital during 2001-2019. For primary and metastatic SS, we also evaluated SS18-SSX immunohistochemistry using needle biopsy and touch imprint cytology specimens from the primary site. RESULTS: SS18-SSX staining was diffusely-strongly positive in all 10 pulmonary metastatic SS cases and the corresponding five primary sites; whereas, it was negative in all 93 clinical and histologic mimics (100% sensitivity and 100% specificity). Further, SS18-SSX staining was also sufficiently positive in the biopsy and cytology specimens. CONCLUSIONS: Immunohistochemistry of the SS18-SSX fusion-specific antibody is useful for the differential diagnosis of pulmonary metastatic SS in clinical practice. This simple and reliable method has the potential to replace traditional genomic tests. However, further studies are warranted in this regard.

Primary mediastinal germ cell tumors - A retrospective analysis of >30 years of experience in a single institution.

BACKGROUND: This study was performed to clarify the treatment outcome of patients with primary mediastinal germ cell tumors (PMGCTs), focusing on the clinical manifestations and management during definitive therapy and long-term follow-up. METHODS: In this study, we retrospectively reviewed the medical records of patients with PMGCTs treated at Shinshu University School of Medicine, and examined the clinical profiles and treatment outcomes of 22 patients (mean age of 29 years) with primary mediastinal GCTs treated at our hospital between 1983 and 2019. RESULTS: Five patients were diagnosed with pure seminoma and 17 had nonseminomatous GCT. A total of 21 patients were treated with cisplatin-based chemotherapy and 15 patients (68.2%) underwent thoracic surgery after chemotherapy. Although all cases of nonseminomatous GCT were negative for tumor markers after cisplatin-based chemotherapy, two cases showed variable GCT cells and two had somatic components (angiosarcoma and rhabdomyosarcoma) in resected specimens. Three relapsed soon after surgery. Growing teratoma syndrome developed during chemotherapy in four cases. Urgent thoracic surgery was performed in three patients, but one case was inoperable. The calculated 10-year overall survival rates were 100% in mediastinal seminoma and 64.7% in NSGCT. During follow-up, second non-GCT malignancies developed in three patients (colon cancer, 190 months; thyroid cancer, 260 months; non-small cell lung cancer, 250 months after the initial chemotherapy) and one patient with primary mediastinal seminoma was associated with multiple type I endocrine tumors. CONCLUSIONS: Our experiences demonstrated that long-term survival and/or cure can be achieved with adequate chemotherapy followed by local surgical treatment even in patients with mediastinal GCTs. However, the clinical manifestations and biological behaviors during and/or after chemotherapy were complex and varied. In addition, the development of secondary malignancies should be taken into consideration for long-term follow-up. Clinicians should be aware of the various clinical features and secondary malignancies in primary mediastinal GCTs.

Synchronous triple primary lung cancer with three different histological subtypes in the same lobe: A case report.

Although the number of patients diagnosed with synchronous multiple primary lung cancer is growing because of increased screening and improved imaging technology, synchronous triple primary lung cancer with different histological tumor subtypes occurring in the same lobe of the lung is extremely rare. In this report, we encountered a 64-year-old male patient with three different types of nodule in the right lower lobe of the lung found on chest computed tomography (CT) scan. We believed that the patient had triple primary lung cancer, and subsequently performed a right lower lobectomy using video-assisted thoracoscopic surgery (VATS). The pathological diagnosis was the same as the presurgical diagnosis, but all the nodules were different histological subtypes. To the best of our knowledge, this is the first case reported in the literature of synchronous triple primary lung cancer with three different histological subtypes in the same lobe of the lung. KEY POINTS: SIGNIFICANT FINDINGS OF THE STUDY: This is the first case of synchronous triple primary lung cancer with three different histological subtypes in each tumor in the same lobe of the lung. WHAT THIS STUDY ADDS: We report the details of the case with immunohistochemical and gene mutation findings, and a literature review of synchronous primary lung cancer.

Three-dimensional computed tomography and indocyanine green-guided technique for pulmonary sequestration surgery.

Patients with pulmonary sequestration are at risk of life-threatening bleeding during lung resection. To perform safe and adequate lung resection in patients with pulmonary sequestration, we utilized the following combination of techniques: (1) three-dimensional computed tomographic (3D-CT) imaging for preoperative planning and intraoperative identification of blood vessels, including aberrant arteries, and (2) intraoperative intravenous administration of indocyanine green (ICG). We describe our surgical technique through three cases who underwent lung resection for pulmonary sequestration using 3D-CT and fluorescence navigation with ICG. Intraoperative identification and division of the aberrant arteries, draining veins, and resection margins of the lungs were successfully completed.

Bone morphogenetic protein-7 expression reflects the high proliferative ability and aggressiveness of thymic epithelial tumors.

BACKGROUND: Bone morphogenetic protein-7 (BMP-7) is a transforming growth factor-ß superfamily member. We examined whether BMP-7 expression in thymic epithelial tumors is associated with their clinicopathological features. METHODS: One hundred and thirty-two clinical specimens were analyzed in this study. The expression of BMP-7 was detected using immunohistochemistry and was scored as 0, 1, 2, or 3 according to its intensity and was then classified as negative (score 0 and 1) or positive (2 and 3). In addition, Ki-67 staining was performed in type B3 thymoma and thymic cancer. RESULTS: The positive ratio of BMP-7 was 80% in thymic cancer and 70% in thymoma type B3. In contrast, the positive ratios of BMP-7 in type B2 (29.1%), B1 (3.7%), AB (26%), and A (31%) were relatively low. The mean Ki-67 labeling index of the BMP-7 positive group (10.1%±5.9%) was significantly higher than that of the BMP-7 negative group (4.9%±5.9%) in type B3 thymoma and thymic cancer (P=0.012). The BMP-7 positive group showed significantly poorer overall survival (OS) than the BMP-7 negative group across all patients with thymic epithelial tumors and in all types of thymomas (P=0.006, P=0.018); however, no difference was observed in thymic cancers. CONCLUSIONS: This study showed that high expression of BMP-7 correlated with a poor prognosis in patients with thymic epithelial tumors, and the expression of BMP-7 was higher in type B3 thymomas and thymic cancers than in other types of thymomas. BMP-7 might serve as a novel prognostic biomarker for thymic epithelial tumors.

Growing thymic granuloma adjacent to a thymic cyst mimicking malignancy: a case report.

An association between thymic cyst and thymic epithelial malignancy has been previously reported. However, several case studies have reported granulomas in the thymus with high metabolic activity, mimicking thymic malignancy. Additionally, an inflammatory response provoked by the rupture of cyst walls has been proposed as a pathogenesis of cholesterol granuloma in the thymus. However, the natural growth history of thymic granuloma remains unclear. We herein report the first case demonstrating the natural growth history of a thymic granuloma adjacent to a thymic cyst. Ten-year follow-up of the thymic cyst revealed a growing nodular lesion with high metabolic activity adjacent to the cyst. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) showed a maximum standardized uptake value of 12.1 in a 2.5-cm solid mass. We performed total thymectomy given a high suspicion of a malignant thymic epithelial tumor. Histopathologic examination revealed a cholesterol granuloma in the thymus, which was directly connected to the thickened region of the cystic wall through a rupture of the wall. This case highlights the importance of considering thymic granuloma as a differential diagnosis for a growing anterior mediastinal nodule with high metabolic activity. Further, the clinical course and histopathologic findings of this case provide supporting evidence for the proposed pathogenesis of thymic granuloma.

Posterior mediastinal ganglioneuroblastoma in an adolescent: A case report and review.

Ganglioneuroblastoma is an uncommon malignant tumor of the sympathetic nervous system, which is considered a disease of children with the majority of cases in patients less than four years old and it rarely occurs in adults. We encountered a very unusual case of a posterior mediastinal ganglioneuroblastoma that developed in a 17-year-old male adolescent who underwent successful excision of the mediastinal mass and remained stable postoperatively. However, he developed lumbago one year after the surgery. Radiographic findings revealed osteolytic lesions in the lumbar vertebra and histological analysis confirmed bone metastasis of ganglioneuroblastoma. Here, we report the clinical course and present a review of the literature regarding adolescent and adult onset mediastinal ganglioneuroblastoma.

Interobserver size measurement variability in part-solid lung adenocarcinoma using pre-operative computed tomography.

BACKGROUND: In the current lung cancer tumor-node-metastasis classification, solid tumor size is used for tumor diameter measurement as the dense component. However, measuring solid tumor size is sometimes difficult and inter-observer variability may increase, particularly in part-solid nodules with ground-glass opacity (GGO). This study aimed to investigate inter-observer size measurement variability in lung adenocarcinoma. METHODS: Of 47 patients with part-solid lung adenocarcinoma who had undergone surgery at our department from January to December 2016, five surgeons and one radiologist undertook unidimensional solid and total size tumor measurements using pre-operative axial computed tomography images, and we assessed inter-observer size measurement variability. Variability was then subclassified into five groups, according to computer tomography-identified tumor morphological characteristics, namely: (I) minimally invasive; (II) peribronchovascular; (III) spiculation/atelectasis; (IV) adjacent to cystic lesion, and; (V) diffuse consolidation and GGO. RESULTS: The mean inter-observer variability was 9.7 mm (solid size) and 7.7 mm (total size). Analysis of the maximum and minimum measurement size values for each patient undertaken showed that the most experienced surgeon and the radiologist measured the minimum size more frequently. To correct for differences in mean tumor diameter in each group, a comparison was made using a coefficient of variation (CV) calculated as the ratio of the standard deviation to the mean. Group I characteristics showed the largest coefficient value for variation in solid size measurement. CONCLUSIONS: Inter-observer measurement variability for solid size was larger than for total size in lung adenocarcinoma. Large variability in group I indicated the difficulty of size measurement for low-grade malignant potential nodules such as adenocarcinoma in situ, minimally invasive adenocarcinoma, and early-stage invasive adenocarcinoma. The possibility of unavoidable size measurement variability should be recognized when deciding on surgical procedures for these diseases.

Thoracoscopic resection of a cystic seminoma of the mediastinum.

Mediastinal seminoma is an uncommon tumor that accounts for 25% of primary mediastinal germ cell tumors, which in turn comprise fewer than 5% of all germ cell tumors. Although CT normally shows a solid, lobulated tumor, mediastinal cystic seminoma has rarely been described. Here, we report a 24-year-old man who presented with a mediastinal cystic tumor that was resected after an 18-month delay via video-assisted thoracoscopic surgery while in the supine position; the procedure involved lifting the chest wall with a subcutaneous Kirschner wire. Pathological examination revealed a mediastinal cystic seminoma. No evidence of recurrence has been noted during 25 months of follow-up. Mediastinal cystic seminoma should be considered in the differential diagnosis of cystic lesions of the mediastinum. Moreover, video-assisted thoracoscopic resection may be an appropriate option for the diagnosis and treatment of such lesions.