Esophageal submucosal tumors represent less than 1% of all esophageal neoplasms . Of these lesions, leiomyomas account for 70–80%. Esophageal lipomas are very rare, accounting for 0.4% of benign tumors of the alimentary tract and usually occur from the cervical and upper esophagus, and are more common in men than in women . On CT examination, lipomas show homogenous lesions containing dense fat. In addition, a smooth surface and “squeeze sign” manifested by deformation in contour and configuration as a result of peristalsis are useful to differentiate lipomas from other benign and malignant lesions . Most esophageal lipomas are small and occur solitary; they do not cause symptoms and may be found incidentally during imaging studies. However, lipomas over 2 cm in diameter tend to cause symptoms such as dysphagia or odynophagia and require treatment. Various treatment options are available, depending on the tumor location and size, and include excision by endoscopy or esophagectomy . However, esophagectomy for benign tumors is advocated as a high invasiveness, and it is important to select a procedure with low risk of morbidity as much as possible. Though enucleation is a useful treatment for esophageal lipomas, injury of esophageal wall during this procedure is a cause of conversion to esophagectomy, so separating the submucosal tissue should be done carefully . In addition, minimally invasive surgery such as thoracoscopic or laparoscopic is related to reduction of postoperative pneumonia and shorter hospital stay compared with open approach . Most large submucosal tumors of the esophagus are removed by thoracotomy . However, because lipomas have well-defined, smooth surface and are quite soft, it was easy to separate the tissue around the tumor and to extract the tumor from small thoracoscopic wound. So, even a giant tumor like our case could be removed by thoracoscopy.
There are few case reports of esophageal lipoma treated with thoracoscopic enucleation. Though Chien-Ying Wang et al.  reported a case of esophageal lipoma removed by thoracoscopic enucleation, the maximum diameter of the tumor was 3.3 cm, which was quite small compared with our case. If a small submucosal tumor is located on the left wall of the esophagus, it is considered possible to perform minimally invasive surgery by enucleation with the left-side transthoracic approach. In our case, the tumor was located on the left side of the esophageal wall. However, since the lipoma was very large and the esophagus was greatly shifted to the right side of the thoracic cavity, the possibility of conversion to esophagectomy was considered. Therefore, we selected a right-side transthoracic approach according to our usual manner of esophagectomy, which can respond to the change of surgery procedure.
The knack of this operation is to develop the appropriate submucosal layer along the tumor surface to preserve the muscle layer, after incision of mucosa of left esophageal wall. Since the tumor was elastic soft, the enucleation was possible with a mucosal incision shorter than the actual tumor size. In addition, after a longitudinal incision of the right esophageal wall, by four retraction sutures placed on the esophageal wall from the outside of the thorax to secure the view of esophageal lumen, we could easily separate the submucosal layer or reapproximate split mucosa layer (Fig. 2d). If the injury or stenosis of the esophageal wall is concerned during thoracoscopic enucleation, esophagectomy and esophagogastrostomy are unavoidable. However, in our case, no stenosis and perforation of the esophageal wall was confirmed by intraoperative endoscopy after suturing. Based on this case, thoracoscopic enucleation with right-side transthoracic approach was considered one of the treatment options even for the giant lipoma located on the left esophageal wall.
However, video-assisted thoracoscopic enucleation and suture can be performed safely only by well-trained surgeons. Watanabe et al. reported the difficulty of thoracoscopic enucleation for an esophageal schwannoma larger than 5 cm and the conversion to subtotal esophagectomy . Recently, the robotic approach for enucleation of esophageal lipoma was reported . Because the robot-assisted surgery offers advantages, including wrist-like movement of the instruments, the three-dimensional camera, and hand tremor filtration, the robotic approach is likely to make surgical procedures, such as tissue dissection and suture, easier.
In addition, there are other suggested surgical plans for enucleation of esophageal lipoma. Tsalis et al.  reported that a Nissen fundoplication was performed to reinforce the esophageal wall and to prevent reflux esophagitis after laparoscopic enucleation of giant lipoma of the lower esophagus, and Jeon et al.  reported that intraoperative esophagoscopy assistance was useful to identify accurate localization of small esophageal submucosal tumors and to evaluate whether there was perforation or stenosis of the esophageal wall after enucleation. Further developments of safe and useful treatment are expected.