CASE REPORT Bowel endometriosis usually involves the serosa or muscularis propria; mucosal/submucosal disease presenting as a colorectal polyp is rare and is the subset most likely to be mistaken for neoplasia or colitis.1–4 A 49-year-old woman with remote, total hysterectomy for fibroids and no known endometriosis underwent screening colonoscopy for intermittent abdominal pain. Colonoscopy demonstrated a solitary 18-mm sessile sigmoid polyp (30 cm from the anal verge) that was removed en bloc with hot snare polypectomy and prophylactic clip placement (Figure 1). Histology showed a well-circumscribed submucosal nodule of endometrial-type glands and stroma elevating the overlying mucosa with hyperplastic surface changes, rare mucosal gland involvement, and no desmoplastic response (Figure 2). Immunohistochemistry confirmed Müllerian origin with ER-positive and PAX8-positive glands and CD10-positive stroma, while intestinal markers (CDX2/CK20) were absent within the lesion and highlighted adjacent native mucosa (Figures 3 and 4). No dysplasia or malignancy was identified. Awareness of this diagnostic pitfall and use of a focused immunopanel can prevent unnecessary staging or surgical referral.3–5 When completely excised endoscopically and without evidence of deep infiltrative disease, conservative management with routine surveillance is appropriate.2Figure 1.: Colonoscopy revealing a solitary 18-mm sessile polyp located 30 cm from the anal verge.Figure 2.: (A) Polypectomy specimen showing a submucosal nodule of endometrial-type glands and stroma elevating the colonic mucosa (H October 26, 2025; Phoenix, AZ. Informed consent was obtained for this case report.
Ahmed et al. (Wed,) studied this question.