V75 - Robotic TAMIS For Colitis Cystica Profunda Mimicking Malignancy

Purpose/Background: Colitis cystica profunda is a rare benign disease characterized by the presence of mucin-filled cysts within the bowel wall. Its exact pathogenesis remains unclear, and some reports have described its coexistence with malignancy. We present the case of a patient with suspected malignancy and a challenging diagnosis of colitis cystica profunda.

Methods/Interventions: A retrospective chart review was conducted.

Results/Outcomes: A 73-year-old male underwent a screening colonoscopy that revealed a rectal neoplasm with a malignant appearance. Pelvic MRI demonstrated a polypoid mass located 5 cm from the anal verge and multiple perirectal lymph nodes. Two consecutive flexible sigmoidoscopies with biopsy revealed a tubulovillous adenoma and subsequently a tubulovillous adenoma with high-grade dysplasia and prominent mucosal prolapse changes. Due to persistent suspicion of malignancy, the patient underwent a robotic transanal minimally invasive surgery (TAMIS) for complete excision. Final pathology demonstrated a tubulovillous adenoma with high-grade dysplasia and extensive colitis cystica profunda. The patient was discharged on postoperative day one and was asymptomatic at follow-up one week later.

Conclusion/Discussion: Colitis cystica profunda is a rare benign condition that can closely mimic invasive adenocarcinoma due to its clinical and radiologic features. It is characterized by mucin-filled cysts lined by benign epithelium. While biopsy may establish the diagnosis, results are often inconclusive, and complete surgical resection may be necessary to exclude malignancy.