EP482 - Colonic Leiomyoma: A Rare Endoscopic Finding

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Purpose/Background: Leiomyomas are benign mesenchymal tumors composed of smooth muscle cells that arise from the muscularis mucosa or propria. Colonic and rectal leiomyomas are rare and account for about 3% of leiomyomas in the gastrointestinal tract. They are typically asymptomatic and often discovered incidentally on endoscopic evaluation because they are submucosal tumors covered with normal epithelium. Larger tumors can cause symptoms such as abdominal pain, obstruction, bleeding, and perforation.

Methods/Interventions: .

Results/Outcomes: We present the case of a 73-year-old male who presented for sigmoidoscopy prior to ileostomy reversal. He initially presented with chronic colonic dilatation refractory to endoscopic decompression and ultimately underwent exploratory laparotomy, partial omentectomy, subtotal colectomy, and end ileostomy after developing pneumatosis in the dilated segment of transverse colon. Patient was asymptomatic upon return for flexible sigmoidoscopy with no abdominal pain, nausea, emesis, weight loss, or change in ileostomy output. Endoscopic evaluation revealed a 4mm submucosal polyp in the recto-sigmoid colon that was resected with cold forceps. Pathology was consistent with submucosal leiomyoma. Immunohistochemical staining revealed bland spindle cells positive for desmin and negative for CD117, DOG1, CD34, and S100. Patient required no further surgical excision and underwent ileostomy reversal without complication.

Conclusion/Discussion: This case highlights a rare gastrointestinal neoplasm, colonic leiomyoma, presenting incidentally on colonoscopy. Histology can be used to distinguish these tumors from the more common adenomas and other mesenchymal tumors like gastrointestinal stromal tumors (GIST). Benign smooth muscle cell tumors are typically well-circumscribed, unencapsulated spindle cell lesions. Immunohistochemical markers including CD117 and DOG1 have been shown to be sensitive and specific for the diagnosis of GIST, while smooth muscle actin (SMA) and desmin are non-specific markers found in smooth muscle cells. The management for these tumors is simple local excision. Small leiomyomas < 2cm can appear as conventional polyps and endoscopic removal with polypectomy or endoscopic mucosal resection is appropriate. For intermediate size lesions, endoscopic ultrasound can be useful to determine if endoscopic resection is feasible or surgical resection is warranted. For larger tumors >5cm, surgical resection is the preferred treatment due to risk of malignant transformation. Further studies are needed to determine the appropriate surveillance interval for patients after leiomyoma excision, but these benign lesions typically do not recur.