[Surgical Case of the Primary Pulmonary Leiomyosarcoma:Report of a Case].

A 70-year-old man was referred for an abnormal chest shadow. Enhanced computed tomography (CT) revealed a well-circumscribed lung tumor of 53 mm in diameter in the left upper lobe with slight enhancement. Positron emission tomography-CT showed a high maximum standardized uptake value for the tumor but no metastasis in the lymph nodes or other organs. Although a definitive diagnosis could not be made by transbronchial biopsy, the tumor was highly suspected to be malignant based on the radiological findings, and a left upper lobectomy with mediastinal lymph nodes dissection was performed for definitive diagnosis and treatment. A pathological examination showed the tumor to be composed of mitotic spindle-shaped cells, which were positive for α-smooth muscle actin, desmin, and caldesmon. The MIB-1 labelling index was 60~70%. According to these pathologic findings, the tumor was identified as a leiomyosarcoma. Metastases to the skin of chest and hilar lymph nodes were noted six months after the surgery for which radiotherapy was performed.

[Thoracoscopic Surgery for Lung Cancer Invading the Superior Chest Wall].

We herein report a case of a 73-year-old man with lung cancer who underwent thoracoscopic right upper lobectomy with combined resection of the superior chest wall. His tumor was 48 mm in diameter and located in the posterior right lung apex involving the chest wall between ribs 1 and 3. The anterior aspects of the ribs 2 and 3 were separated using forceps under thoracoscopic vision. The first rib could be released from the tumor by peeling off the parietal pleura. An 8 cm incision was made posteriorly between the scapula and vertebrae to obtain the posterior aspect of the ribs 2 and 3. After separating the pulmonary vessels and bronchus, en bloc resection of the superior sulcus tumor was completed. Thoracoscopic chest wall resection of the superior sulcus tumor can be an alternative to the Paulson posterolateral-paravertebral thoracotomy approach, which can cause severe postoperative pain and limited range of motion of the shoulder joint.

Laser-Trélat sign improved after the resection of a tiny ground-grass nodule: a case report.

The Laser-Trélat sign refers to eruptive seborrheic keratoses accompanied by internal malignancies, mainly abdominal advanced ones. Detailed associations remain unclear, and the skin lesions do not improve with the treatment of internal malignancies in half of the patients. Herein, we report a rare case of Laser-Trélat sign that improved after resection of a 0.6-cm pulmonary ground-glass nodule: adenocarcinoma in situ. The patient requested the resection with the hopes of improving the skin lesions, though immediate resection was not indicated oncologically. With informed consent, despite possible failure in improving cutaneous diseases, thoracoscopic partial resection of the right lower lobe was performed. Fortunately, her seborrheic keratoses substantially improved after the resection, without exacerbation. To our knowledge, this is the first report describing such a clinical course. It is essential to inform patients regarding the indication of treatment for internal malignancy and its limitation in improving eruptive seborrheic keratoses.

[The Outcome of Second Anatomical Pulmonary Resection for Ipsilateral Metachronous Lung Cancer].

INTRODUCTIONS: When the first intervention for lung cancer is anatomical resection, the ipsilateral repeat anatomical resection for metachronous second lung cancer becomes technically challenging. Herein, we report the outcomes of second anatomical pulmonary resection for ipsilateral metachronous lung cancer at our institution. SUBJECTS: Sixteen consecutive patients[ 10 men and 6 women, average age 70( range 59~81) years] were reviewed in this retrospective study. These patients underwent ipsilateral repeat anatomical resection for metachronous second lung cancer between 2009 and 2020. RESULTS: All case required right-sided lung resections. The previous interventions of patients included upper lobectomy, lower lobectomy, middle lobectomy, S2 segmentectomy, and S6 and S10a segmentectomy in 9, 4, 1, 1, and 1 case, respectively. The second surgical interventions were middle lobectomy, S6 segmentectomy, upper lobectomy, lower lobectomy, S1 segmentectomy, and S2 segmentectomy, in 6, 4, 2, 2, 1, and 1 case, respectively. Postoperative complications occurred in three patients. The median follow-up period was 53.5 months. Three patients died during the follow-up period. Of the 13 patients still alive, 6 had recurrence. The five-year overall survival rate was 80%. CONCLUSIONS: Although only a few cases were assessed, the prognosis after second anatomical pulmonary resection for ipsilateral metachronous lung cancer at our institution was satisfactory.

[Completion Pneumonectomy for the Recurrence of Lung Cancer].

INTRODUCTIONS: The morbidity and mortality after completion pneumonectomy (CP) are reportedly high. We, herein, report the outcomes of CP at our institution. SUBJECTS: Nine consecutive patients [7 men and 2 women, average age of 72 years(range 44~84 years)] who underwent CP for recurrence of lung cancer during 2012~2018 were retrospectively reviewed. RESULTS: Right-sided sleeve CP was performed in two cases and left-sided CP in seven cases. The indications for surgery were lymph node metastasis of the cancer, pulmonary metastasis, and bronchial stump recurrence in 4, 3, and 2 cases, respectively. Postoperative complications occurred in six patients. One of the patients who underwent right sleeve pneumonectomy developed bronchopleural fistula and died 68 days after the surgery. The mean follow-up period was 33 months, and four patients died during follow-up. Of the 5 patients still alive, 4 had no recurrence and 1 had recurrence in the stump of the main bronchus. The five-year overall survival rate was 78%. CONCLUSIONS: Although only few cases were assessed, the prognosis after CP at our institution was relatively good.

Intrapulmonary solitary fibrous tumour: a case report.

Solitary fibrous tumours (SFTs) mainly originate from the visceral pleura and may protrude to the thoracic cavity, but intrapulmonary SFTs are extremely rare. We describe a rare case of SFT arising in the right lung of an 83-year-old man who underwent surgical excision. Chest computed tomography (CT) revealed a 10-mm tumour in the lower lobe of the right lung. The size of tumour gradually increased and reached 17 mm 2 years after the first radiologic examination. Considering the possibility of malignancy, wedge resection of the right lower lobe was performed via video-assisted thoracic surgery. Microscopically, the tumour consisted mainly of spindle-shaped cells. Immunohistochemical staining indicated the tumour was positive for CD34, STAT6, vimentin and bcl-2, but negative for cytokeratins, D2-40 and S-100. Based on the histological findings, the tumour was diagnosed as SFT. The patient has been in good health for 6 months since the surgery.

Can the Japanese National Clinical Database risk calculator predict long-term survival of patients who undergo palliative segmentectomy for primary lung cancer?

OBJECTIVES: Selection criteria for palliative limited surgery in patients with non-small cell lung cancer (NSCLC) can vary by institution or surgeon. We retrospectively reviewed outcomes of poor-risk patients who underwent palliative segmentectomy (PS), using the National Clinical Database Risk Calculator (RC). METHODS: We retrospectively analyzed medical records of patients with NSCLC tumors ≥ 20 mm and consolidation/tumor ratios ≥ 0.5 on computed tomography, who underwent PS from January 2009 to March 2016. Median follow-up time was 47 months (range 2-102 months). RESULTS: We enrolled 67 patients (median age: 73.0 years), of whom 54 received thoracoscopic surgery and 28 received medial lymph-node dissection. The RC's mean predictive probability rate for perioperative mortality or severe complications was 7.1%. Of the 67 patients, 24 patients (43.0%) suffered post-surgical complications, including 2 (3%) who died in hospital; 17 eventually suffered NSCLC recurrences and/or metastases, 11 eventually died from NSCLC, and 17 died from other diseases. Five-year overall survival (OS) was 59.4%. When the patients were divided into high-risk (HR) and low-risk (LR) groups based on the RC, 5-year OS was significantly less in the HR group (43.9%) than in the LR group (82.2%; P < 0.05). CONCLUSION: The RC, which was developed primarily to determine perioperative risk, can predict long-term prognosis for compromised patients who undergo PS.

Left mediastinal node dissection after arterial ligament transection via video-assisted thoracoscopic surgery for potentially advanced stage I non-small cell lung cancer.

BACKGROUND: Left mediastinal node dissection during lung cancer surgery can be difficult because paratracheal and subcarinal lymph nodes are concealed by mediastinal structures. Arterial ligament transection (ALT) offers a wide surgical view of concealed mediastinal spaces, thus enabling extended en bloc lymph node dissection (LND). We analyzed surgical outcomes of patients who underwent extended LND after ALT via video-assisted thoracoscopic surgery (VATS) for potentially node-positive clinical stage I non-small cell lung cancer (NSCLC). METHODS: We retrospectively investigated the medical records of 75 patients who had undergone extended mediastinal node dissection after ALT via VATS for potentially node-positive NSCLC at our centers during the period from September 2008 through November 2015. Operative data and rates of overall survival (OS), in addition to mortality and morbidity, were analyzed in relation pathological stage and nodal stage. RESULTS: Operative time was 238±58 minutes, and an average of 32.7±12.9 hilar and mediastinal lymph nodes were dissected. Lymph node metastases were detected in 34 patients (6 pN1 patients, 27 pN2 patients, and 1 pN3 patient). Mediastinal lymph node metastases were detected around the carina (stations 2L, 4L, and 7) in 19 of 27 patients with pN2 cancer. Nineteen patients had a total of 24 postoperative complications. Recurrent nerve paralysis was the most frequent complication (n=11) but resolved in eight patients during follow-up. Survival rates at 3 and 5 years were 92.2%/88.4%, 100.0%/60.0%, and 87.7%/81.0% for p-stage I, II, and III, respectively, and 92.2%/88.4%, 100.0%/60.0%, and 87.4%/80.7% for pN0, pN1, and pN2, respectively. CONCLUSIONS: Extended mediastinal node dissection after ALT allowed detection of lymph node micrometastases in selected patients with potentially node-positive left NSCLC and may improve outcomes.

Pleuroperitoneal Communication and Ovarian Cancer Complicating Peritoneal Dialysis: A Case Report of a Patient with End-Stage Kidney Disease.

Peritoneal dialysis has been a widely accepted modality for treating end-stage kidney disease, but a regular dialysis schedule can be seriously disrupted by various comorbid conditions requiring surgical intervention. A 40-year-old woman who had been receiving peritoneal dialysis was sequentially but separately complicated by pleuroperitoneal communication and ovarian cancer. Despite the need for temporary interruption of her peritoneal dialysis schedule, it was successfully resumed after the relevant surgeries for each disease. Several concerns regarding overall postoperative dialytic management strategies, including how to deal with the peritoneal dialysis catheter during the postoperative period as well as how long peritoneal dialysis should be interrupted, which remain an unresolved issue in the field of nephrology, are also discussed.

Establishment of highly metastatic KRAS mutant lung cancer cell sublines in long-term three-dimensional low attachment cultures.

Decreased cell-substratum adhesion is crucially involved in metastasis. Previous studies demonstrated that lung cancer with floating cell clusters in histology is more likely to develop metastasis. In the present study, we investigated whether cancer cells in long-term, three-dimensional low attachment cultures acquire high metastatic potential; these cells were then used to examine the mechanisms underlying metastasis. Two KRAS-mutated adenocarcinoma cell lines (A549 and H441) were cultured and selected on ultra-low attachment culture dishes, and the resulting cells were defined as FL (for floating) sublines. Cancer cells were inoculated into NOD/SCID mice via an intracardiac injection, and metastasis was evaluated using luciferase-based imaging and histopathology. In vitro cell growth (in attachment or suspension cultures), migration, and invasion were assayed. A whole genomic analysis was performed to identify key molecular alterations in FL sublines. Upon detachment on low-binding dishes, parental cells initially formed rounded spheroids with limited growth activity. However, over time in cultures, cells gradually formed smaller spheroids that grew slowly, and, after 3-4 months, we obtained FL sublines that regained prominent growth potential in suspension cultures. On ordinary dishes, FL cells reattached and exhibited a more spindle-shaped morphology than parental cells. No marked differences were observed in cell growth with attachment, migration, or invasion between FL sublines and parental cell lines; however, FL cells exhibited markedly increased growth potential under suspended conditions in vitro and stronger metastatic abilities in vivo. A genomic analysis identified epithelial-mesenchymal transition (EMT) and c-Myc amplification in A549-FL and H441-FL cells, respectively, as candidate mechanisms for metastasis. The growth potential of FL cells was markedly inhibited by lentiviral ZEB1 knockdown in A549-FL cells and by the inhibition of c-Myc through lentiviral knockdown or the pharmacological inhibitor JQ1 in H441-FL cells. Long-term three-dimensional low attachment cultures may become a useful method for investigating the mechanisms underlying metastasis mediated by decreased cell-substratum adhesion.

Giant solitary fibrous tumor of the pleura with high-grade sarcomatous overgrowth accompanied by lipid-rich, rhabdomyosarcomatous, and pleomorphic components: A case report.

RATIONALE: Solitary fibrous tumors are mesenchymal tumors presenting as fibroblastic neoplasms with prominent branching vascular patterns, which are often generated from the pleura. Most solitary fibrous tumors are benign; however, some can turn malignant. High-grade sarcomas from solitary fibrous tumors include multidirectional histopathological components. PATIENT CONCERNS: We describe our experience of a giant high-grade sarcoma with mixed components generated from a solitary fibrous tumor of the pleura in a 67-year-old female patient presenting with cough and left-sided chest pain. The patient had been diagnosed with a pleural mass in the left chest by X-ray about 30 years earlier. However, the tumor was allowed to grow, without surgical intervention, for a long time. INTERVENTIONS: Thoracic surgeons performed the removal of the giant pleural tumor; the tumor measured 18.0 × 14.5 × 10 cm in size, and was considered a giant tumor generated from the pleura of the left chest cavity. DIAGNOSES: The surgically removed tumor was solid and light brownish, and included myxoid and arabesque pattern lesions. The tumor also showed hemorrhagic and necrotic lesions. Moreover, spindle cells with less atypia, resembling fibroblasts, were noted. These spindle tumor cells were CD34- and Stat6-positive, suggesting a solitary fibrous tumor. Some of the spindle tumor cells were surrounded by thick collagenous fibers. Considering that the tumor originated from the parietal pleura, the tumor was defined as a solitary fibrous tumor in origin. The tumor also comprised high-grade sarcomatous components; these included lipid-rich, rhabdomyosarcomatous, and pleomorphic components. The high-grade sarcoma component included bizarre tumor cells with severe atypia. OUTCOMES: Tumor recurrence occurred in the left chest about 4 months after the surgery, and the patient died 8 months postoperatively. LESSONS: The present case clearly demonstrates that a solitary fibrous tumor can develop into high-grade sarcomatous overgrowth, including lipid-rich, rhabdomyosarcoma, and pleomorphic sarcoma components, if left untreated for a prolonged period. This case provides profound insights about the natural history, histogenesis, differentiation, and malignant transformation of solitary fibrous tumors.

Peripherally located endobronchial hamartoma mimicking aspergilloma: a case report.

We herein report the case of a 75-year-old man with a pulmonary hamartoma that mimicked aspergilloma on chest computed tomography (CT). A CT scan performed to assess an asymptomatic lesion detected on a screening chest radiograph showed a 1.3-cm diameter nodule with an air crescent sign in the left lower lobe. A diagnosis of aspergilloma was made and the patient treated with an antifungal agent for 1 year, following which he underwent radical surgery because of failure of the radiologic lesion to resolve. Pathologic examination of the resected specimen showed an endobronchial hamartoma within the B9 periphery. Peripherally located hamartomas can develop within the peripheral bronchi resulting in an air crescent appearance on radiological images.

Extraction bag lavage cytology during video-assisted thoracoscopic surgery for primary lung cancer.

OBJECTIVES: Sample extraction from the thoracic cavity through an intercostal space during video-assisted thoracoscopic surgery can result in cancer cell contamination by tumour crushing and tumour cell extravasation, and may have adverse effects on the surgical outcome. Lavage cytology of the sample extraction bag was investigated to clarify the risk of cancer cell spillage and identify the clinicopathological features associated with susceptibility to cancer cell spillage during extraction. METHODS: Lavage cytology of the sample extraction bag was investigated in 464 patients with negative pleural lavage cytology who underwent lung resection for primary lung cancer via video-assisted thoracoscopic surgery between January 2010 and December 2012. The surgical procedures, pathological findings and clinical course were evaluated by hospital record review. RESULTS: The incidence of positive bag lavage cytology (BLC) was 13.6%. Statistically significant factors associated with susceptibility to BLC positivity were tumour size, standardized uptake value of positron emission tomography, pathological features such as pathological N score, pleural invasion, vascular invasion and papillary-predominant adenocarcinoma. Among patients with Stage I lung cancer, the survival rate was significantly lower in the BLC-positive group than in the BLC-negative group. CONCLUSIONS: BLC positivity can be related to oncological characteristics such as tumour invasiveness and adhesiveness as opposed to tumour size and surgical margin, and may help to determine the prognosis of Stage I lung cancer. The sample extraction bag must be carefully manoeuvred through the intercostal space to prevent cancer cell dissemination to the chest wall or thoracic cavity.

Surgical outcomes after superior vena cava reconstruction with expanded polytetrafluoroethylene grafts.

OBJECTIVES: Graft occlusion is a problem after superior vena cava (SVC) reconstruction for thoracic malignancy. Expanded polytetrafluoroethylene (ePTFE) is considered to be an optimal material for venous reconstruction. METHODS: We reviewed the hospital records of 13 patients who underwent complete resection of thoracic malignancy invading the SVC, including SVC reconstruction with ePTFE grafts. Single bypass grafting was performed in two patients (one right-sided, one left-sided) and double bypasses grafting was performed in the other patients. All patients received antithrombotic therapy after surgery. Eight patients died of recurrence or other disease during the follow-up period (range 5-41 months). RESULTS: Of the 24 grafts in 13 patients, graft patency was confirmed in 20 grafts in 9 patients at a mean time follow-up time of 47.8 ± 50.0 months after surgery. In the remaining four grafts in four patients, occlusion was diagnosed at a mean time of 1.25 ± 0.50 months after surgery. All obstructed grafts were left-sided bypass grafts in patients who underwent double bypass grafting, and did not result in SVC syndrome. CONCLUSIONS: SVC reconstruction with ringed ePTFE grafts was safe and had good outcomes. In patients who underwent double bypasses grafting, the left-sided bypass grafts were susceptible to occlusion.

An open-label study of algorithm-based treatment versus treatment-as-usual for patients with schizophrenia.

OBJECTIVE: The use of an algorithm may facilitate measurement-based treatment and result in more rational therapy. We conducted a 1-year, open-label study to compare various outcomes of algorithm-based treatment (ALGO) for schizophrenia versus treatment-as-usual (TAU), for which evidence has been very scarce. METHODS: In ALGO, patients with schizophrenia (Diagnostic and Statistical Manual of Mental Disorders, fourth edition) were treated with an algorithm consisting of a series of antipsychotic monotherapies that was guided by the total scores in the positive and negative syndrome scale (PANSS). When posttreatment PANSS total scores were above 70% of those at baseline in the first and second stages, or above 80% in the 3rd stage, patients proceeded to the next treatment stage with different antipsychotics. In contrast, TAU represented the best clinical judgment by treating psychiatrists. RESULTS: Forty-two patients (21 females, 39.0 ± 10.9 years-old) participated in this study. The baseline PANSS total score indicated the presence of severe psychopathology and was significantly higher in the ALGO group (n = 25; 106.9 ± 20.0) than in the TAU group (n = 17; 92.2 ± 18.3) (P = 0.021). As a result of treatment, there were no significant differences in the PANSS reduction rates, premature attrition rates, as well as in a variety of other clinical measures between the groups. Despite an effort to make each group unique in pharmacologic treatment, it was found that pharmacotherapy in the TAU group eventually became similar in quality to that of the ALGO group. CONCLUSION: While the results need to be carefully interpreted in light of a hard-to-distinguish treatment manner between the two groups and more studies are necessary, algorithm-based antipsychotic treatments for schizophrenia compared well to treatment-as-usual in this study.

[Stump recurrence after pulmonary metastasectomy from colorectal cancer].

Pulmonary metastasectomy with wedge resection is an ideal procedure in terms of less invasiveness and preservation of respiratory function, while local recurrence is a major problem. The goal of this study was to verify risk factors of stump recurrence after pulmonary metastasectomy from colorectal cancer. Pulmonary metastasectomies including 112 operations for 131 lesions in 85 patients with colorectal cancer were performed in our department since March, 2005 until the end of 2010. In our cases, stump recurrence significantly occurred in patients who underwent wedge resection than segmentectomy or lobectomy. Stump recurrence developed in 14 operations among 62 wedge resections (recurrence rate: 23%). Diameter more than 10 mm and distance between pleura and deepest end of the tumor (depth value) more than 14 mm were risk factors as stump recurrence. Tumor diameter and depth value can be a decisional factor for wedge resection in pulmonary metastasectomy in the colorectal cancer patients.

Identification of CCDC6-RET fusion in the human lung adenocarcinoma cell line, LC-2/ad.

Rearranged during transfection (RET) fusions have been newly identified in approximately 1% of patients with primary lung tumors. However, patient-derived lung cancer cell lines harboring RET fusions have not yet been established or identified, and therefore, the effectiveness of an RET inhibitor on lung tumors with endogenous RET fusion has not yet been studied. In this study, we report identification of CCDC6-RET fusion in the human lung adenocarcinoma cell line LC-2/ad. LC-2/ad showed distinctive sensitivity to the RET inhibitor, vandetanib, among 39 non-small lung cancer cell lines. The xenograft tumor of LC-2/ad showed cribriform acinar structures, a morphologic feature of primary RET fusion-positive lung adenocarcinomas. LC-2/ad cells could provide useful resources to analyze molecular functions of RET-fusion protein and its response to RET inhibitors.

Pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma in Sjögren's syndrome showing only the LIP pattern radiologically.

A 49-year-old woman with a 20-year history of Sjögren's syndrome (SS) was incidentally found to have an abnormal chest X-ray along with dyspnea and desaturation. Chest CT findings showed multiple cystic shadows, ground glass opacity, and small nodule-like lymphocytic interstitial pneumonia (LIP), which have been previously reported. She was diagnosed by surgical lung biopsy to have mucosa-associated lymphoid tissue (MALT) lymphoma. It was difficult to detect the presence of lymphoma by the use of only CT findings. Pulmonary involvement of SS occurs in various forms so that SS patients with pulmonary involvement should undergo open biopsy to reach a definitive diagnosis.

[Clinicopathological study of small lung cancer (diameter of 2 cm or less) by uptake value of 18F-fluorodeoxyglucose].

18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) for lung cancer may be a biomarker for malignancy as well as a useful tool for detection of nodal involvement and distant metastasis. The goal of this study was to clarify a relationship between clinicopathological findings and maximum standardized uptake value( SUVmax) obtained by preoperative PET in patients with non-small cell lung cancer in diameter of 2 cm or less. Between January 2008 and April 2011, 124 patients( 54 men and 70 women) with non-small cell lung cancer in diameter of 2 cm or less undergoing lobectomy or segmentectomy were enrolled. The relationship between SUVmax and clinicopathological findings as tumor diameter, histological type, pleural invasion, vascular invasion, lymphatic permeation and nodal involvement were analyzed. Correlation between SUVmax and findings such as vascular invasion and lymphatic permeation showed relatively strong in the patients with adenocarcinoma, on the contrary to the correlation in the patients with non-adenocarcinoma. No tumor showing SUVmax of 2 or less showed vascular invasion and/or lymphatic permeation as well as nodal involvement in any patients with adenocarcinoma. SUVmax of the primary tumor in diameter of 2 cm or less, can be a useful biomarker which indicates a surgical candidate for sublobar pulmonary resection as well as mediastinal nodal dissection, especially in patients with adenocarcinoma.

[Clinical outcome after video-assisted thoracic surgery (VATS) for clinical stage I lung cancer with pathologically nodal involvement].

The lymph node dissection with video-assisted thoracic surgery( VATS) was technically feasible and the remnant lymph nodes and tissues were 2% to 3%, which seems acceptable for clinical stage I lung cancer. Surgical outcome after VATS for clinical stage I lung cancer with pathologically nodal involvement, however, remains unclear. Medical records of 72 patients who had clinical stage I non small cell lung cancer with pathologically nodal involvement( pN1:21 patients, pN2:51 patients) and underwent VATS lobectomy or segmentectomy with mediastinal dissection between January 2005 and December 2010, were retrospectively reviewed. Postoperative recurrence and survival were studied. Remnant nodal recurrence occurred in 8 patients with pN1 (recurrence rate 38%) and 15 patients with pN2 (recurrence rate 29%). The 1- and 3-year disease free survival rate was 87% and 68%. The 1- and 3-year survival rate was 100% and 79%. This study suggested that VATS is acceptable for patients with clinical stage I lung in terms of survival rate, cancer with pN1. In a view point of remnant nodal recurrence, a more skillful dissection procedure is required.