PC1206: Abdominal Pain, Diarrhea, Nausea, and Weight Loss Related to a Mucinous Neoplasm: A Rare Diagnosis in a Pediatric Patient

Introduction: Appendiceal mucinous neoplasms are rare tumors of the appendix that account for less than 1% of all cancers. Most are detected in adults, usually diagnosed in the fifth or sixth decade of life, with a slight female predilection. They are extremely uncommon in the pediatric age group.

Case Description: A 17-year-old male with a family history of Crohn's disease presented to a gastroenterology clinic with a 9-month history of non-bloody diarrhea associated with intermittent nausea, abdominal pain, and 20-pound weight loss. The physical exam was unremarkable. Stool studies including culture, occult blood, calprotectin, ova and parasite, Giardia, H. pylori, and disaccharides were negative. Celiac panel, thyroid panel, ESR, CRP, CBC, and CMP were normal. Upper endoscopy was unrevealing. A large 2.5 x 2.5 x 2.4 cm cecal polypoid mass was visualized during the colonoscopy and resected endoscopically, resulting in a subsequent small cecal perforation that was unable to be closed endoscopically due to the location. Laparoscopic surgery revealed the residual appendix was dilated with myxoglobulosis protruding from both the lumen of the appendix and cecum, with leakage of mucin noted into the operative field. No gross mucin deposits were noted at the time of surgery. Surgery resected the cecal defect completed with an appendectomy. The histopathology diagnosis was of a low-grade appendiceal mucinous neoplasm pT3Nx with no extension beyond the mesoappendiceal margin, and without cellular mural invasion or desmoplasia. Screening tumor markers CA 19-9, CA-125, and CEA were unremarkable. CT and subsequent MRI of the abdomen and pelvis revealed no evidence of peritoneal involvement. As his main risk of recurrence is development of pseudomyxoma peritonei (PMP), surveillance plans include CT abdomen and pelvis and tumor markers every 6 months for the next two years, then yearly follow-up.

Discussion: Appendiceal mucinous neoplasms account for 0.4%-1% of all gastrointestinal malignancies in the US and are present in 0.2%-0.3% of appendectomy specimens. Serious complications of these tumors include intestinal obstruction, intestinal perforation, mucocele rupture, and pseudomyxoma peritonei. Treatment and prognosis for appendiceal neoplasms depend on the histopathologic characteristics of the tumor, TNM stage, tumor grade, and presence of peritoneal disease. The Chicago Consensus on Peritoneal Surface Malignancies recommends surveillance or consideration of intraperitoneal chemotherapy for fully-resected low-grade appendiceal mucinous neoplasms with perforation, primarily due to the risk of post-resection development of pseudomyxoma peritonei.

Conclusion: Our case report identifies the importance of having an index of suspicion for appendiceal malignancy in those with abdominal pain and weight loss, despite the rarity of the disease.