Appendiceal mucinous adenocarcinoma presenting as cecal intussusception: A rare case report

Appendiceal mucinous adenocarcinoma (MACA) is an uncommon malignancy, representing less than 0.5% of gastrointestinal cancers. Clinical presentation is often nonspecific, which can delay diagnosis. Intussusception as an initial manifestation is exceptionally rare in adults. We report the case of a 63-year-old man with no significant medical history who presented with acute abdominal pain, vomiting, and diarrhea. Examination revealed a periumbilical mass, and inflammatory markers were elevated. Contrast-enhanced CT demonstrated a large cecal intussusception extending to the transverse colon with a few right iliac fossa lymph nodes. The patient underwent laparotomy with partial cecectomy, which revealed indurated cecal tissue. Histopathology confirmed mucinous adenocarcinoma of the appendix measuring 3.5 cm, low-grade, invading the subserosa/mesoappendix (pT3), with negative margins and no nodal metastasis (0/12). The final stage was pT3N0M0 (AJCC stage IIA). Given the absence of nodal involvement, adjuvant chemotherapy was not administered, and the patient was managed with structured surveillance including periodic imaging and tumor marker assessment. This case illustrates a rare presentation of MACA as the lead point for cecal intussusception in an adult. It underscores the importance of considering appendiceal tumors in the differential diagnosis of bowel obstruction and highlights the role of prompt surgical resection for diagnosis and management.