Appendiceal Mucinous Neoplasm: A Case of an Incidental Finding

Appendiceal mucinous neoplasms (AMNs) are uncommon gastrointestinal tumors characterized by mucus accumulation in the appendix. Patients may complain of acute appendicitis-like symptoms with other alarming features, but approximately half of the cases of AMNs are found incidentally on imaging. Early diagnosis and management of these neoplasms are important to prevent malignant progression and complications such as bowel obstruction and pseudomyxoma peritonei. We report a case of a 28-year-old female who initially presented with vomiting and acute left lower abdominal pain radiating to the left flank. Computed tomography (CT) revealed a 1.5 mm stone in the left ureteral vesicular junction and a 2.3 x 2.4 x 5.2 cm cystic tubular mass at the base of the cecum, suspicious of an appendiceal mucocele. An elective laparoscopic appendectomy was performed on this admission, which was converted to a right hemicolectomy due to the pathologic finding of a focally high-grade AMN on intraoperative frozen specimen pathology. This report aims to provide an example of a case of an incidental AMN and how it was diagnosed and managed surgically. AMNs are rare tumors that originate from the appendix and can pose diagnostic and therapeutic challenges due to their diverse clinical presentations and variable histopathological features. The majority of cases of AMNs are discovered in middle-aged individuals (40-50 years of age) after an appendectomy is performed and examined by pathology. This case report aims to describe a rare presentation of a 28-year-old female patient with an incidental finding of AMN on a CT scan of the abdomen while being worked up for suspected nephrolithiasis. We will provide a comprehensive overview of a unique presentation of AMN, highlighting its clinical manifestations, diagnostic approach, and management strategies. We present the case of a 28-year-old female patient who presented to the emergency department with complaints of acute left lower quadrant abdominal pain radiating to the left flank and vomiting. After an initial assessment and workup, which included lab investigations and imaging, a diagnosis of unilateral hydronephrosis due to a calculus of the ureterovesical junction was made. However, there was also suspicion of an appendiceal mucocele, as evidenced by a CT scan of the abdomen and pelvis. On admission day one, under the care and management of the urology team, she passed the stone with complete resolution of the presenting symptoms. On hospital day two, she underwent an elective laparoscopic appendectomy followed by a right hemicolectomy due to findings of high-grade mucinous neoplasm on the resected frozen specimen near the base of the appendix. AMN was an incidental finding based on CT imaging and macroscopic findings, which was later confirmed by histopathological assessment and report.