Polypoid colorectal endometriosis with abundant leiomyoma-like smooth muscle cell proliferation treated by endoscopic resection

A 55-year-old female patient with abdominal pain was referred for resection of an atypical lesion in the descending colon after office-based colonoscopy. Endoscopic visualization of the estimated 15-mm nodular lesion with a broad pedicle at 11 o´clock appeared not consistent with adenoma, although minor mucosal changes, potentially related to previous biopsies were discernible (Fig. 1A). Corresponding to the endoscopic aspect, no submucosal injection of indigo carmine was achievable, however, endoscopic resection was, nonetheless, pursued to achieve tissue diagnosis (Fig. 1B). Therefore, the lesion was cautiously snare resected in a superficial manner (Fig. 1C), and post-interventional evaluation of the resection defect excluded perforation (Fig. 1D). The further clinical course was uneventful, and, with a view to histopathology, the patient was referred for gynecological care. Indeed, pathology indicated an abundant leiomyoma-like nodular smooth muscle cell proliferation with minor reactive epithelial changes with endometrial glands and stroma in between (Fig. 2A), Closer-up scrutinization of endometrial tissue elements excluded dysplastic changes (Fig. 2B). Dedicated immunohistochemistry for endometrial structures highlighted the localization around the nodular smooth muscle cell proliferation (Fig. 2C) with desmin immunoreactivity (Fig. 2D). Intriguingly, hormonal receptor immunohistochemistries indicated marked positivity in the endometrial tissue plane as well as within the leiomyoma-like nodule (Fig. 2E, F). The latter finding rather suggests a reactive nature over coincident leiomyoma.