This case highlights the importance of carefully assessing the luminal contents and surrounding areas when considering acute appendicitis. Though the findings here are retrospectively quite evident, the endoluminal mass in the tip of the appendix was initially missed and the patient was taken to surgery for appendectomy and drainage of the retroperitoneal abscess.

Pathology revealed a low-grade adenocarcinoma of the appendix with at least T3 staging, but suspicious for T4a. Subsequent imaging, confirmed by exploratory laparotomy, showed peritoneal carcinomatosis. Over the course of more than one year, the peritoneal implants showed slow growth in the patient's desire to forgo chemotherapy.

In cases of radiologically suspected tumor mimicking an uncomplicated acute appendicitis, the surgeon should be notified preoperatively as the surgical approach will likely be altered.

Case courtesy of Dr Odile Prosmanne, abdominal radiologist at the Center Hospitalier de l'Université de Montréal.