Supplemental Material for: Cecoappendiceal Endometriosis Presenting as a Cecal Traction Diverticulum: A Case Report

Objectives: Cecoappendiceal endometriosis is rare and frequently mimics colorectal neoplasia, making preoperative diagnosis challenging. We report the first documented case of a cecal traction true diverticulum caused directly by endometriosis-associated smooth muscle hypertrophy and subserosal fibrosis.Case Presentation: A 42-year-old nulliparous woman presented with an incidentally discovered malignant-appearing polypoid cecal mass on colonoscopy. Abdominal CT demonstrated a 1.5-cm enhancing lesion at the proximal appendix. Laparoscopic wedge resection of the cecum and appendix was performed. Histology revealed deep endometriosis (>5 mm) with dramatic smooth muscle hypertrophy (muscularis propria 12 mm vs. normal ~0.37 mm; >30-fold increase) in both the cecum and appendix. A true traction diverticulum—confirmed histologically to contain all three bowel wall layers—had formed as a direct mechanical consequence of progressive endometriosis-driven hypertrophy and fibrosis. Immunohistochemistry demonstrated estrogen-receptor–positive glands and CD10-positive stroma; beta-catenin negativity excluded mesenteric fibromatosis.Conclusion: This is the first documented case of endometriosis-induced cecal traction diverticulum, establishing a new mechanistic concept in intestinal endometriosis. Endometriosis-driven myoproliferation combined with subserosal fibrosis may generate sufficient mechanical traction to invert the cecal wall into a diverticular configuration. Endometriosis should be included in the differential diagnosis of cecal diverticular lesions in reproductive-aged women, and pelvic MRI should be considered for preoperative characterization before attributing such lesions to neoplasia or diverticulitis.