Appendiceal adenocarcinoma complicated by retroperitoneal abscess

Case contributed by Francis Fortin
Diagnosis certain


Acute abdominal pain

Patient Data

Age: 85 years
Gender: Male

Initial abdominopelvic CT


Retroperitoneal abscess seen to arise from the tip of the appendix. This was initially read as complicated appendicitis. However, notice how there is an expansive tissue-density rounded lesion in the appendiceal tip. This should raise suspicion of an underlying tumor. Also, note how little fat stranding there is surrounding the tip of the appendix. This is also quite unusual if considering typical acute appendicitis.

Annotated images

Annotated image

On the annotated coronal image, one can clearly see the appendix (blue) arising from the base of the cecum (green), with the rounded lesion (red) representing the suspected tumor. The retroperitoneal abscess is highlighted in yellow.

On the annotated axial images, one can also appreciate the zone of ulceration (purple) in the suspected appendiceal tip tumor (red) communicating with the retroperitoneal abscess (yellow).

PostOp PET-CT a few mth later

Nuclear medicine

Post-operative PET-CT scan shows high uptake posterior to the cecum, suspicious for residual tumor and/or peritoneal carcinomatosis.

Case Discussion

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.

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