Resection of EMPA in the upper mediastinum using a transcervical approach with or without partial sternotomy may be common, but resection by video-assisted thoracic surgery (VATS) is common in the deep mediastinum. VATS is an approach with less surgical trauma, decreased associated morbidity, shorter hospital stays, and superior cosmetic results. In recent years, several cases of robot-assisted thoracic surgery (RATS) for EMPA have been reported [8–11]. Ward et al. reported that robot-assisted complete thymectomy for EMPA, which provides excellent visualization of the mediastinum, is effective in reducing PTH and calcium levels and is safe with no morbidity or mortality .
Prior to the surgical removal of an EMPA, the surgeon should attempt to understand the status of the patient's cervical parathyroid glands . Parathyroid tissue function has profound clinical implications, and leaving a patient with loss of parathyroid function should be avoided when possible. Autografting of hyperfunctional parathyroid tissue may be necessary. Therefore, thoracic surgeons should be aware of this scenario, and if necessary, an endocrine surgeon should be included in the management of the patient . 99mTc-MIBI and neck US are the initial imaging modalities for patients with PHPT. Regardless of the imaging modality used for localization, the surgeon must exercise caution because no examination is 100% accurate in diagnosing a single adenoma as the cause of PHPT . In this case, 99mTc-MIBI showed accumulation in the anterior mediastinal nodule, which appeared as a single solid lesion. The EMPA was removed with the surrounding thymus without damaging the capsule; however, there were small parathyroid gland tissues in the surrounding thymus. This indicates that excision of the main tumor alone may not normalize parathyroid function. In fact, even the high-volume center has an operative failure rate of 13%-22% [6, 13]. Therefore, it is extremely important to monitor the PTH levels during surgery.
There is a report in the field of head and neck surgery that dissemination occurs during parathyroidectomy [1, 14]. It is important not only to handle the tumor gently, but also to know the exact location of the tumor. In this case, the patient was a lean woman with little fat in the mediastinum, and the location of the tumor was immediately identifiable. However, most EMPAs are buried in the thymus and adipose tissue, and it may be difficult to identify lesions during surgery even after careful examination before surgery. The intraoperative radio-guide method in which 99mTc-MIBI is intravenously injected at the time of surgery [15, 16] and a staining method in which MB is intravenously injected [17, 18] have been reported as identification methods. Moreover, in recent years, near-infrared fluorescence imaging using indocyanine green has been applied to identify the parathyroid gland intraoperatively . The radio-guide method is not suitable for EMPAs in the deep mediastinum because of the effect of 99mTc-MIBI uptake into the myocardium and great vessels . Pseudohypoxemia is a problem in anesthesia management using the MB staining method, but it can be solved using near-infrared spectroscopy .
In conclusion, we successfully resected an EMPA using RATS with intraoperative PTH monitoring. However, histopathologically, small parathyroid gland tissues may remain in the surrounding thymus. Hence, we believe that a strict follow-up is required to monitor parathyroid function following RATS.