Appendiceal Adenocarcinoma Presenting as a Rectal Polyp.

Area of Science:

• Gastroenterology
• Surgical Oncology
• Colorectal Surgery

Background:

• Appendiceal adenocarcinoma commonly presents as an incidental mass or with right lower quadrant pain.
• Local organ involvement is an uncommon initial presentation of appendiceal cancer.

Observation:

• A 75-year-old female presented with hematochezia and a rectal polyp mimicking a lesion within a diverticulum.
• Endoscopic mucosal resection failed, prompting referral for low anterior resection.
• Preoperative imaging revealed an enlarged appendix adjacent to the rectum.

Findings:

• Intraoperative findings showed the appendix densely adherent to the rectal wall.
• Pathology confirmed appendiceal adenocarcinoma invading through the rectal wall.
• An en bloc resection of the distal sigmoid, proximal rectum, and appendix was performed.

Implications:

• This case represents a unique presentation of appendiceal adenocarcinoma mimicking a rectal polyp due to direct rectal wall invasion.
• En bloc resection is essential for complete tumor removal and minimizing peritoneal spread.
• Abnormal findings adjacent to gastrointestinal pathology may indicate locally advanced disease from surrounding organs, necessitating thorough preoperative investigation.