Benign Yet Deceptive: A 19-Year-Old Male with A Rectal Mass Mimicking Carcinoma, Ultimately Diagnosed as Colitis...

We report a rare case of a healthy 19-year-old male with a rectal mass mimicking advanced carcinoma on endoscopy and imaging. Final histopathology following excisional biopsy confirmed a rare benign entity-colitis cystica profunda (CCP). Recognizing this condition is essential to prevent misdiagnosis and unnecessary radical treatment.

A 19-year-old male with no past medical or surgical history presented with several weeks of non-bloody diarrhoea. Colonoscopy revealed an ulcerated, irregular, friable mass 7 cm from the anal verge with infiltrative features. A computed tomography scan of the chest, abdomen and pelvis and pelvic magnetic resonance imaging demonstrated a rectal mass invading the muscularis propria and multiple regional lymph nodes (largest ≈6 mm), suggesting T4N2 staging. Two colonoscopies by different endoscopists with deep biopsies showed no malignancy. A third excisional biopsy with expert histopathology confirmed CCP. The patient was managed conservatively and remained asymptomatic at 12-month follow-up with stable endoscopic and radiologic findings.

Although rare, CCP should be considered in the differential diagnosis of rectal masses-especially in young patients-when imaging and endoscopy mimic malignancy but histology is benign. A multidisciplinary approach, with repeat or excisional biopsy and close clinicopathologic correlation, is key to avoiding overtreatment.

Colitis cystica profunda is a benign condition that may closely mimic advanced rectal carcinoma on both endoscopic and radiologic evaluation, leading to significant diagnostic confusion.Persistent discordance between imaging and histology warrants deeper biopsies and multidisciplinary team review before considering radical intervention.In young adults presenting with rectal masses, clinicians must consider both malignant (e.g., adenocarcinoma, lymphoma) and rare benign entities such as colitis cystica profunda. Careful pathology review, correlation with imaging, and genetic counselling when appropriate are essential.