Acute appendicitis is one of the most common causes of acute abdominal pain. Undiagnosed or untreated appendicitis can lead to serious complications. The most frequent complication of acute appendicitis is perforation with subsequent formation of a localized periappendiceal abscess or diffuse bacterial peritonitis. Late occurring complications following undiagnosed appendix perforation can pose a diagnostic challenge due to uncharacteristic clinical and imaging presentation. Herein, we describe late findings of undiagnosed perforated appendicitis that on 18F-FDG PET/CT mimicked recurrent endometrial carcinoma disease in a 67-year-old woman.