Abstract: OBJECTIVE: To discuss the surgical treatment modalities and summarize the treatment experience of giant chest tumors in children. METHODS: For lung tumors occupying the entire thoracic cavity, a median thoracic incision was used to deal with the hilum, while other lung tumors and posterior mediastinum tumors were treated with a conventional posterior-lateral incision for radical tumor resection. For anterior mediastinal tumors, a median thoracic incision or anterolateral incision was adopted as appropriate, and sharp plus blunt method was used to separate until complete resection of the tumor. Results: One of the three cases with preoperative diagnosis of lung tumor underwent left total pneumonectomy. In the other case, the right lower middle lobe of the lung was resected, and the pathology report was pulmonary blastoma in both cases. One of the two anterior mediastinal tumors was a spindle cell tumor and the other was a malignant nerve sheath tumor of thymic origin, both of which were completely resected. The pathological report of all four cases was neuroblastoma. Conclusion: Surgical indications, surgical approach and operator’s experience directly determine the outcome of children with giant tumors in the chest. Keywords: children, giant chest tumor, surgery, pneumoblastoma, neuroblastoma We define a giant chest tumor in children as one that is more than 10 cm in diameter or occupies more than 1/3 of the volume of one side of the chest cavity, or even the entire side of the chest cavity. The tumor originates from multiple organs and parts of the lung, mediastinum, chest wall, etc. The pathological types are rare, and most of them are mainly reported in the literature. This group of cases is reported as follows. Materials and methods I. Materials: From February 2005 to September 2008, a total of 9 children with giant tumors in the chest, aged 11 months to 10 years (mean ± years), 5 males and 4 females, were treated surgically. The preoperative diagnosis of pulmonary masses was 3 cases, one case occupied the whole left thoracic cavity, another case occupied the whole right lower lobe of the lung, and another case had a huge occupancy in the left lower thorax, and the chest CT suggested “left lower lung mass”; 2 cases of anterior mediastinal tumors, both of which were occupancies in the right anterior mediastinum, had huge masses protruding into the right thoracic cavity, and the chest CT suggested possible thymoma; 4 cases of posterior mediastinal There were 4 cases of posterior mediastinum tumors, 2 on each side, and the chest CT suggested the possibility of neurogenic tumor. The smallest mass was more than 10 cm in diameter and the largest one occupied one side of the chest cavity. CT of the chest showed no enlarged lymph nodes in the mediastinum except for an isolated mass on the left aortic arch in one child. The clinical manifestations of the children mainly included cough, sputum, chest tightness, shortness of breath, fever, and chest and back pain (see the table below). Laboratory tests were normal except for 2 cases with elevated WBC, and liver and renal functions and tumor markers were normal. Clinical manifestations Symptoms Cough Chest tightness, shortness of breath Fever Chest and back pain Dry cough with sputum Low fever High fever Number of cases Method: For lung tumors occupying the whole thoracic cavity, a median chest incision was made, the pericardium was opened to ligate the pulmonary veins and pulmonary arteries, the bronchial stump was closed with a bronchial stump closure device, and then the hilum was separated from the adhesions and infiltrates in the chest, and finally the lymph nodes were cleared; for other lung tumors, a conventional postero-lateral incision was made. For other lung tumors, a conventional posterior-lateral incision is used for radical lung tumor surgery. For anterior mediastinal tumors, a median or anterolateral chest incision is used as appropriate; for posterior mediastinal tumors, a posterolateral incision is used. The mediastinal tumors were separated under the pericardium where the pericardium was present, and the mediastinum and chest wall infiltrates were separated by sharp and blunt methods until the tumor was completely removed. One of the children with preoperative diagnosis of lung tumor underwent total left pneumonectomy. In the other case, the right lower middle lobe of the lung was resected and the lymph nodes were negative. One case died of tumor metastasis 7 months after total lung surgery; one case is still alive 19 months after surgery. In another case, a mass was seen intraoperatively attached to the left 6th and 7th ribs and protruded into the thoracic cavity, the outer membrane was still neat and irregular in shape, and a large mass of chest wall mass was excised, and the intraoperative frozen pathology report was: “small cell malignant tumor of the left pleura”, but the final immunohistochemistry report was: “rib Ewing sarcoma of the left chest wall”. One of the two anterior mediastinal tumors was a spindle cell tumor and the other was a malignant nerve sheath tumor of thymic origin with multiple tumor-like nodules on the surface and intact envelope, both of which were completely resected. In four cases, the posterior mediastinal tumors were smooth, tough and elastic, and the mediastinal and chest wall tumors were infiltrative in their attachment surface. One case was reported as “small cell malignant tumor” by intraoperative freezing, but the pathology report of all four cases was neuroblastoma in the end. They are still being followed up 12, 15, 23 and 30 months after surgery. Discussion Pulmonoblastoma, or pleural pneumoblastoma, is a highly aggressive malignant tumor.1 It is mostly seen in childhood and is associated with embryonic dysplasia, and is a rare malignant tumor of the lung. Most pediatric pneumoblastomas occur in the periphery or pleura and mediastinum and present late with symptoms. It is highly misdiagnosed.2 It consists of tumorigenic epithelial luminal and embryonic mesenchymal components of varying degrees of differentiation. Pleural pneumoblastoma in the pediatric period is not of the same tissue origin as pneumoblastoma that occurs primarily in adults. Early and complete surgical excision of the mass is advisable for treatment. Surgical excision of the mass has both prognostic and therapeutic value, and chemotherapy and radiotherapy should be intensified if excision is incomplete. Ewing sarcoma is the second most common malignant bone tumor in children. It is of neuroectodermal cell origin and belongs to the Ewing family of tumors along with neuroectodermal blastoma, neuroepithelioma, and Askin’s tumor. The tumor is of neuroectodermal cell origin and belongs to the Ewing family of tumors, along with neuroectodermal blastoma, neuroepithelioma and Askin tumor. The combination of preoperative adjuvant chemotherapy, followed by local surgical resection and radiotherapy, and postoperative chemotherapy has significantly improved the 5-year survival rate.3 However, Ewing sarcoma of the chest is difficult to diagnose preoperatively. Spindle cell tumors, which are confined pleural interrogative tumors. In contrast, confined pleural mesothelioma is rare. They are mostly solitary, round or oval, firm grayish-yellow nodules with smooth margins, mildly lobulated, peritoneal, and varying in size from a few centimeters in diameter in small ones to occupying one side of the chest in large ones. They can weigh up to several kilograms. The tumor has a wide contact surface with the pleura and projects from the pleura to the pleural cavity. Microscopic examination of the tumor tissue is not uniform in all parts. In benign cases, the fibrous component is predominant, often consisting of spindle cells and occasionally epithelial cells, and the predominance of epithelial cell component suggests a malignant tendency. Malignant nerve sheath tumors originating in the chest are rare,4 and even rarer in children with thymic origin. Malignant nerve sheath meningiomas are generally less malignant and most have a good prognosis for surgical resection, although metastases can occur. Tumors with an envelope have a high rate of complete resection and a better outcome. In contrast, malignant nerve sheath tumors with histologic features of choroidal differentiation or rhabdomyoblastoma, i.e., salamander tumors, indicate a high degree of malignancy and a poor prognosis. Neuroblastoma originates in the adrenal medulla or paravertebral sympathetic nervous system and develops before the age of 5 years in 2/3 of cases. It has a rapidly progressive clinical presentation, can metastasize early, and is extremely malignant, but is characterized by self-resolution and in vitro induction of differentiation to maturity. Neuroblastoma is difficult to diagnose and cannot be differentiated from other small round cell tumors in children.5 One case in our group was misdiagnosed as a small cell malignancy by cryopathology. Neuroblastoma requires comprehensive treatment, and surgery has an important, but not exclusive, role in NB. Although giant thoracic tumors in children involve a variety of pathological types depending on the site of growth, the key to treatment is: (1) the mastery of surgical indications. This is closely related to the operator’s familiarity with chest anatomy and knowledge of chest imaging. In general, most children in this group can be abandoned for surgery or only have an exploratory biopsy of the thorax due to the huge mass and the difficulty of separation, which makes surgery extremely risky, so that the child is deprived of the best treatment. We developed a meticulous surgical plan through correct evaluation of preoperative X-ray imaging data and other data, and resected the tumor completely, obtaining a better outcome. (2) Choice of surgical route. The surgical route is the key to decide whether the tumor can be removed, whether other important organs will be damaged, how much blood will be lost intraoperatively, and whether serious complications will occur. For example, for huge pulmonary blastoma, we adopt a median sternal incision to open the pericardium and deal with the hilar vessels, trachea and then the adhesions between the lung and chest wall and lymph nodes, which reduces bleeding and avoids the result that the operation cannot be continued because the tumor is huge and the conventional posterior lateral incision cannot expose the hilar structures. For anterior mediastinal tumors, we advocate using a median sternal incision to facilitate dissection of the tumor and to avoid damage to the innominate vein, etc., which may cause hemorrhage or prevent continuation of the surgery due to involvement of the innominate vein. (3) Experience of the surgeon. Preoperative chest radiograph of a 4-year-old child with pneumoblastoma occupying the entire right side of the chest cavity Right side of the chest cavity after resection of the tumor (right whole lung) by median incision Removed surgical specimen Figure 1 Preoperative chest radiograph of a child with giant mesenchymal chondrosarcoma Figure 2 Postoperative chest radiograph of a child with giant mesenchymal chondrosarcoma Preoperative CT image of a rare giant mediastinal tumor (spindle cell tumor) Postoperative radiograph of a rare giant mediastinal tumor (spindle cell tumor)