APPENDICEAL MUCINOUS ADENOCARCINOMA: A RARE CAUSE OF CECAL-COLON INTUSSUSCEPTION

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Background: Adult appendiceal mucinous neoplasms are rare malignancies that occur in approximately 3500 cases per year or 0.12 cases per million people. Furthermore, intussusception in adults is equally rare, with a rate of 2.5 cases per million, representing 5% of all reported cases, 1% of all bowel obstructions, 0.08% of all abdominal surgeries, and 0.02% of all hospital admissions. In this report, we describe a rare case of mucinous adenocarcinoma of the appendix presenting as a large bowel obstruction with intussusception and colonic wall pneumatosis.

Case: The patient is a 46-year-old male, with no significant past medical or surgical history, who presented with three weeks of vague abdominal pain. The workup revealed a white blood cell count of 7.8 K/mcL, lactate of 5 mmol/L, and a CT scan finding of cecal to transverse colonic intussusception with colonic wall pneumatosis. He was taken emergently to the operating room and underwent an exploratory laparotomy which revealed an appendiceal mass, as the lead point of the intussusception, with features suggestive of invasive mucinous adenocarcinoma. A right hemicolectomy was performed. Pathology results revealed a stage III B (pT3 N1 aM0) appendiceal mucinous adenocarcinoma (Figure 1). Following an uncomplicated hospital course, the patient was discharged home with an outpatient colonoscopy and an oncology follow-up for chemotherapy with folinic acid, fluorouracil, and oxaliplatin (FOLFOX).

Discussion: Appendiceal mucinous adenocarcinomas account for 3.3% of all cases of colonic intussusception in adults. These neoplasms are staged according to the TNM classification system, and range from Low-grade Mucinous Neoplasms (LAMNs), High-Grade mucinous neoplasms (HAMNs), to mucinous adenocarcinomas. In the event of perforation, mucin-producing cells are dispersed, leading to pseudomyxoma peritonei. There is a wide range of treatment options depending on the extent of disease; however, guidelines and practices vary between treatment centers. Surgical intervention includes appendectomy alone (small, localized tumors), right hemicolectomy, or cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (in the setting of intraperitoneal metastasis). Colonoscopy should be performed in all patients to exclude synchronous lesions which occur in up to 42% of cases. In the treatment of metastatic adenocarcinomas and HAMNs, adjuvant systemic chemotherapy is indicated. The recurrence rate varies substantially depending on the stage and grade of the disease, and there is no universally accepted surveillance strategy. For our patient with a Stage III B well-differentiated mucinous appendiceal adenocarcinoma, with appropriate upfront management and follow-up, the overall 5-year survival is high at 82.6%.

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