A 69-year-old woman with a history of tubular adenoma (5mm in the descending colon) returned for a follow-up colonoscopy. A 9mm sessile polyp (Fig. 1A) was detected in the transverse colon, and complete resection was achieved with a cold snare. Histopathology revealed colonic mucosa containing smooth muscle proliferation suggestive of leiomyoma (Fig. 1B and C). There was no need for any further follow-up beyond the recommended 5-year screening colonoscopy.

Figure 1.

A) A 9mm sessile polyp detected in the transverse colon during colonoscopy. B) Hematoxylin and eosin, 40× magnification. Colonic mucosa containing smooth muscle proliferation suggestive of leiomyoma. C) Hematoxylin and eosin, 200× magnification. The leiomyoma is composed of benign smooth muscle cells with dense pink cytoplasm, arranged in intersecting fascicles. There is no mitotic activity, necrosis, or atypia to suggest a malignant smooth muscle tumor (i.e., leiomyosarcoma).

Leiomyomas are smooth muscle tumors arising from the muscularis mucosa and are infrequent in the gastrointestinal tract. These can be sessile, pedunculated, or "adenomatous-like" and are more commonly found in the esophagus or stomach. Both surgery and endoscopic removal are suitable. However, endoscopy carries a higher perforation risk. The injection of saline solution beneath the mucosal layer is a common method to determine the origin of polyploid lesions. A positive lift sign signifies the tumor’s shallow depth, allowing endoscopic removal.

Conversely, a negative lift sign indicates deep muscle tissue involvement and is a contraindication for endoscopic removal. Distinguishing leiomyomas from conventional polyps is challenging, leading to misidentifications. Despite this, the prognosis is favorable, with rare recurrence.