Leiomyomas may appear throughout the entire gastrointestinal tract but are rarely seen in the colon-rectum and represent only 3% of cases [5]. They can be found throughout all ages but present an increase in frequency in individuals who are over 60 years of age. Colonic leiomyomas are frequently asymptomatic and are often discovered on routine endoscopic evaluations [2]. Larger leiomyomas (> 2 cm) can cause symptoms such as abdominal pain, constipation or bleeding [6].
Colonic leiomyomas are smooth muscle tumors that constitute the largest group of primary gastrointestinal non-epithelial neoplasms and are majoritarily benign; however, some may be locally aggressive or even malignant. Even benign looking tumors can metastasize. Consequently site, tumor size, histological appearance, and mitotic count should be considered in predicting the malignant potential of these tumors [1].
Although colonic leiomyomas appear predominantly as sessile lesions, they can also form subpedunculated or pedunculated lesions [2]. In a retrospective study, Choi et al. analyzed 22 patients with polypoid leiomyoma in the colon over a 3-year period. The most lesions were small (< 1cm), asymptomatic, and found incidentally during a screening colonoscopy. All tumors arose from or involved the muscularis mucosa, and most presented as small sessile polyps, with the exception of 5 pedunculated leiomyomas [6]. In another study, Agaimy and Wünsch reported that all 67 colorectal leiomyomas originating from the muscularis mucosae were well-circumscribed sessile polypoid masses [2]. It is noted that in only rare cases subpediculated colonic leiomyomas appear.
Our case describes a subpedicled polypoid lesion located in the rectosigmoid transition. After endoscopic resection, anatomopathological analysis was performed and diagnosed as submucous leiomyoma.
Colonic leiomyomas, particularly those < 2 cm in size, can be successfully treated by endoscopic resection, as most tumors arise from the muscularis mucosa [6]. To avoid the risk of perforation in endoscopic removal, lesions are usually lifted with the submucosal injection technique. A positive lifting sign indicates that the tumor can be completely resected endoscopically, whereas a non-lifting sign indicates that the tumor is deeper and this therapy is contraindicated [6, 4]. Surgical resection is recommended in tumors with suspected malignancy, in addition to patients with failed endoscopic closure or delayed recognition of perforation [6].
This case appears to be the first mesenchymal leiomyoma resected by underwater endoscopic mucosectomy, a new and well established method for the resection of benign colonic lesions. A fundamental part of this procedure is the submucosal injection, which elevates the lesion separating the submucosa from the muscle layers, consequently reducing the risk of perforation and thermal damage to adjacent layers. However, in some cases the injection can hinder the procedure, especially when lesions are nonpolypoid. Another possible complication is the transferring of cells to deeper layers when the needle goes through the lesion. Binmoeller et al. published the first case series of a new option for mucosectomies without the need of submucosal injections in 2012 [7]. These resections were performed with complete immersion of the lesion and underwater diathermic loop resection. This method was developed through the observation that during underwater immersion the mucosa and submucosa floated while the muscle layer remained distended.