The open surgical approach has generally been accepted as the gold standard for thymoma resection [6–9]. However, over the last decades, both thoracoscopic and, more recently, robotic approaches have been introduced into the thoracic field and also applied to thymectomy. Several data were published regarding minimally invasive thymectomy, reporting interesting outcomes and emphasizing less operative trauma, shorter hospital stays, preserved pulmonary function, and superior cosmetic results [10–13]. However, only a few major series have reported the surgical results of RATS surgery for thymoma [14–16]. In the surgical treatment of non-invasive thymoma, the choice of RATS or VATS remains controversial.
Our short-term surgical outcomes showed the safety and efficacy of RATS for Masaoka stage I thymoma. The duration of surgery was the same in both groups, and there was no statistically significant difference between the two groups (P=0.168) in the amount of blood lost. However, RATS thymectomy was less invasive, as indicated by the significant decrease in the mean or median postoperative stay in the RATS group. Furthermore, there were no serious postoperative complications in the RATS group. In addition, no case was converted to open surgery, and no case required blood transfusion. Although the follow-up period was short, there was no early recurrence of thymoma. Our results suggest that RATS thymectomy is tolerated in patients with early-stage thymoma.
An important point is that we use ultrasonic devices in RATS. Great care must be taken to avoid vascular and nervous injuries. Bleeding is the most serious complication and should be kept in mind during this operation. Special attention must be paid because venous drainage of the gland to the innominate vein involves thin vessels; each must be isolated from the thymic veins, coagulated, and cut with an ultrasonic device to minimize the amount of bleeding. In the RATS series, no patients experienced conversion to an open procedure. However, in the VATS series, one patient experienced conversion to an open procedure because of injury to the left innominate vein during electric cautery for dissection. Although small, this tool is excellent in terms of handling and indispensable for this operating method.
Nevertheless, with regard to oncological outcomes, some criticisms of minimally invasive approaches still exist. First, the possibility of tumor spread into the chest cavity has been reported in some papers [6, 17, 18]. Agasthian et al.  reported a local recurrence rate of 3.4% in patients who underwent VATS thymectomy for thymoma, while two recent papers compared VATS and open approaches for thymomas. Cheng et al.  observed no local or pleural disease recurrence for stage II thymoma in either the open or VATS groups. Similar results were published by Pennathur et al.  in a larger comparative study, reporting no significant difference in disease recurrence or overall survival between the two groups. In our small series, despite the fact that the follow-up period was short, we observed no local or pleural recurrence. We believe that the robotic system facilitates differentiation of thymoma from normal thymic tissue and allows for safe manipulation. Nevertheless, an important factor that likely affected the success of the minimally invasive approach is the dimension of the lesion. In our series, the mean thymoma dimension was 30.4±7.9 mm in VATS and 29.05±7.7 mm in RATS, similar to the dimensions reported in the above-mentioned comparative studies of the VATS approach [19, 20]. However, the indolent nature of thymomatous disease necessitates a long follow-up  of 10 years to evaluate the survival and disease-free rates. Thus, further multi-institutional studies involving larger series are necessary.
Because high costs are one of the main points of criticism voiced in connection with robotic-assisted operations, we recently evaluated the hospitalization costs of thymectomy for various minimally invasive approaches. Use of robots is significantly more expensive, and we demonstrated high costs compared with VATS (P <0.01). These high costs are primarily caused by the expensive robotic instruments, which can be reused only a limited number of times .
The present study has some limitations, including its retrospective nature, which may have resulted in a selection bias. Moreover, the study sample was small and the follow-up period short. However, this is an initial experience resulting from gained skill in robotic surgery for thymoma, and the main aim was to analyze the safety and technical feasibility of the robotic approach for early-stage thymomas. In fact, few data regarding the robotic approach with a focus on thymoma have been published, and our small series is the largest one to our knowledge.