Rare Large Intestinal Lesions: A Case Series of Colonic Leiomyomas.

Introduction: Colonic leiomyomas are benign smooth muscle tumors of the large intestine. Although more commonly seen in the esophagus, leiomyomas of the colon are occasionally discovered during colonoscopies with the large intestine accounting for only 3% of gastrointestinal leiomyomas. Appropriate excision and staining can differentiate them from similar mesenchymal growths. Current guidelines do not offer recommendations on follow-up for this type of lesion, but recurrence rates are low based on reported cases. The purpose of this case series is to report 10 cases of this rare form of colonic lesion and investigate their recommended follow-up timelines and recurrence rates.

Case series: We report the cases of 10 histologically proven colonic leiomyomas identified between the years 2015 and 2025 within one hospital system. Eighty percent of these were discovered on screening colonoscopy in asymptomatic patients. Staining of these leiomyomas to confirm diagnosis included a positive actin and/or desmin stain and a negative CD34, CD117, DOG1 and/or S100-protein stain to rule out similar appearing gastrointestinal stromal tumors. The average follow-up recommendation made for these patients to repeat colonoscopy or imaging was 3.35 years. There are no documented recurrences of leiomyomas within these cases to date.

Conclusion: Although colonic leiomyomas are benign, these lesions should be excised and appropriately stained to differentiate them from similar appearing smooth muscle tumors. Although there are no current guidelines on the timeline to follow up, exploration of cases and investigation of recurrence rates can contribute to the development of specific follow-up recommendations when endoscopists encounter these rare lesions.