Appendiceal Cancer: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Appendiceal neoplasms are rare (approximately 1-2 per 100,000 per year), frequently discovered incidentally during appendectomy for appendicitis. Main types: well-differentiated neuroendocrine tumors (NETs, ~50%), mucinous neoplasms (LAMN, ~24%), goblet cell adenocarcinoma (~10%), and colonic-type adenocarcinoma (~11%). Ruptured mucinous tumors cause pseudomyxoma peritonei (PMP).

Appendiceal NETs arise from enterochromaffin cells; most are small (<2 cm) and incidentally discovered. Mucinous neoplasms (LAMN) harbor KRAS mutations and may rupture to cause PMP. Lynch syndrome and FAP increase adenocarcinoma risk. The vast majority of appendiceal tumors are sporadic without identifiable risk factors.

Most appendiceal NETs less than 2 cm are asymptomatic incidental findings during appendectomy. Larger tumors or mucinous neoplasms: appendicitis-like right lower quadrant pain, increasing abdominal girth from accumulating peritoneal mucin (PMP), bowel obstruction, and ovarian masses from mucin dissemination (frequently misdiagnosed as ovarian cancer). Carcinoid syndrome is rare unless greater than 2 cm with liver metastases.

CT abdomen/pelvis for characterization and staging. CEA and CA 19-9 for mucinous tumors; chromogranin A and 24-hour urine 5-HIAA for NETs. 68Ga-DOTATATE PET for staging appendiceal NETs. MRI for hepatic metastasis assessment. Peritoneal extent determined at diagnostic laparoscopy using the peritoneal cancer index (PCI) score. Histological classification follows PSOGI 2016 consensus for mucinous neoplasms.

Appendiceal NETs ≤2 cm: appendectomy is curative. NETs >2 cm or goblet cell: right hemicolectomy. Localized LAMN without perforation: appendectomy. Adenocarcinoma: right hemicolectomy. PMP with low peritoneal cancer index: cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC with mitomycin C ± oxaliplatin) at specialized centers. Systemic chemotherapy for advanced adenocarcinoma: FOLFOX or FOLFIRI. NETs: somatostatin analogues; PRRT for SSTR2-positive progressive disease.

Appendiceal NETs ≤2 cm after appendectomy: 5-year OS exceeds 95%. LAMN with optimal CRS/HIPEC: 10-year OS approximately 60-90%. Colonic-type adenocarcinoma: 5-year OS approximately 45-60% overall. Goblet cell adenocarcinoma: 5-year OS approximately 50-75% (Stage II), approximately 15-30% (Stage IV). PMP outcomes depend heavily on specialist center experience and peritoneal disease extent.