Synchronous cancer is defined as simultaneous tumor occurrence in two or more organs or locations. In the gastrointestinal tract, the most common combination is gastric cancer associated with colorectal cancer. Eom et al.  reported that colorectal cancer occurring simultaneously with gastric cancer accounts for 20.1% of all synchronous cancers. As a result of the development of diagnostic tools and a well-organized national health insurance system, the detection of gastric cancer, combined with colorectal cancer, has increased in Korea [4,5].
GIST has been known as a submucosal tumor that can occur anywhere from the esophagus to the anus. The stomach (70%) and small intestine (25%) are the most common locations for its occurrence . GIST is diagnosed via endoscopy or computed tomography, and although the treatment may be slightly different depending on the location or size of the tumor, the treatment of choice is surgical resection. There have been several cases in which gastric GIST was found simultaneously with gastric cancer [13,14]. Moreover, although several studies have reported on multiple GISTs [15,16], the exact mechanism of their occurrence remains to be elucidated . However, to the best of our knowledge, the present case is the first reported case in which EGC with three gastric GISTs combined with synchronous colon cancer was detected.
The patient first came to our hospital for further evaluation of a simple gastric GIST. During diagnostic workup, we accidentally detected another gastric GIST, an EGC, and colon cancer. Finally, we detected another GIST in the stomach specimen postoperatively. From the diagnosis to the treatment, various departments collaborated in the present case, ie, a multidisciplinary approach was organically applied with the involvement of Departments of Surgery (Division of Gastrointestinal and Colorectal), Gastroenterology, Radiology, Pathology, and Nuclear Medicine. Close consultation and multidisciplinary care are important parts of modern medicine, and these are even more necessary for patients with multiple cancers. Owing to the development of video conferencing and well-designed cell phone applications, it is possible to seek the opinions of other specialists without a face-to-face conversation.
An EGC could be removed via endoscopic submucosal dissection, and GISTs could be treated via wedge resection. However, two of the GISTs in our patient were large and located in the upper body of the stomach. Thus, we were concerned about complications such as a stricture, and we decided to perform total gastrectomy for the stomach lesions. After performing lymph node dissection, we deemed near-total gastrectomy to be feasible, leaving a small proximal part of the stomach without esophageal transection. Consequently, avoiding the serious complication of anastomosis of esophagojejunostomy, the EGC was removed with a sufficient proximal margin, and the GISTs were resected completely. Subsequently, conventional colorectal surgery was performed.
In our patient, all the procedures were laparoscopically performed. A long midline incision would have been inevitable if we could not proceed with the laparoscopic technique for gastrectomy and colectomy. This type of incision could lead to several complications, such as increased postoperative pain, reduced ambulation, and increased length of postoperative hospital stay . Laparoscopic surgery has recently become a popular option and has been gradually replacing the conventional open surgery in several fields of abdominal surgery. The popularization of three-dimensional scopes, development of automatic linear staplers, and improvement in the surgical skills of surgeons are important factors for the recent trends of laparoscopic surgery. For treating EGCs, the laparoscopic approach has become a treatment of choice according to the domestic guideline . Likewise, indications for laparoscpic treatment of colorectal cancer have been gradually expanding .
Lifestyle as well as environmental and genetic factors act synergistically in the pathogenesis of synchronous cancer. Lifestyle factors such as the use of tobacco, alcohol, and nitrosamines influence cancer pathogenesis . Moreover, patients with history of multiple cancers should undergo a complete evaluation including family history and genetic counseling. Genetic testing is usually performed when multiple synchronous colorectal cancers occur simultaneously at a young age or when concurrent cancers occur in other organs . However, when gastric and colorectal cancers occur simultaneously, both have usually been found to be primary lesions. We could not find any particular risk factors, including genetic mutations, in this case, and there are few specific genetic tests for patients with concurrent cancers .
We experienced a rare case of a patient with an EGC with multiple gastric GISTs combined with synchronous colon cancer. In the future, if similar cases are accumulated in multiple studies, it would be necessary to investigate genetic mutation testing for these synchronous cancers.