Whether to perform up-front surgery or surgery after induction chemotherapy was considered for the excision of this tumor. Following the preoperative biopsy, the patient was diagnosed with a type A thymoma, a colossal tumor with an ARSCA. Surgery was performed for several reasons; first, when considering the combined resection of the tumor and LBCV, it was judged that complete resection was possible. Second, steroid pulse therapy has an insignificant effect on type A thymomas ; however, there was concern about postoperative sternal dissection and mediastinitis due to steroids. Third, chemotherapy could make it difficult to control a potential postoperative infection due to bronchiectasis and the detection of nontuberculous mycobacteria in the sputum. Finally, we were afraid to miss the opportunity for surgery due to the onset of side effects associated with chemotherapy and tumor growth.
Since thymoma poses a risk of dissemination upon unintended damage to the capsule, the tumor should be resected as an en-bloc mass. However, in advanced-stage malignant tumors, the conflict between achieving oncologic R0 resection and patient safety remains an unsolved issue. The separation of tumors should also be considered under special circumstances [4,5,6]. In this case, preoperative evaluation of CT images showed that the border between the caudal side of the tumor and the superior vena cava was partially obscured, which may not result in complete resection. However, the tumor was divided naturally along the constriction when the LBCV that ran between the tumors was detached. A good field of view was acquired to identify the ARSCA and LRLN that ran deep in the tumor and surgical field; blood vessels could be safely detached with a clear visual field, and essential nerves could be preserved using IONM. While we believe that a complete resection was achieved, the tumor was unintentionally divided. Therefore, the risk of recurrence may have increased, and strict follow-up is required.
IONM assesses muscle-induced electromyography (EMG) by placing electrodes on the muscle and directly electrically stimulating the innervating nerve with a nerve stimulation probe during surgery to monitor nerve function . It is a widespread,confirmatory method that has been recognized to be helpful in identifying and preserving recurrent laryngeal nerves in locally advanced thyroid cancer, reoperation cases, and giant goiter cases. Typically, when anesthesia is introduced, an EMG endotracheal tube is placed so that the electrode is in contact with the tracheal arytenoid muscle, making it is possible to detect the contraction of the cricothyroid muscle during recurrent laryngeal nerve stimulation. In this case, the EMG endotracheal tube could not be placed due to the size of the tumor, and an electrode was inserted into the patient's right shoulder for monitoring.
In conclusion, the thymoma that grew extensively from the neck to the upper mediastinum and was associated with an ARSCA, was resected. We were thus able to safely remove the tumor without complications. The use of IONM was useful in identifying the NRILN and LRLN.