Appendiceal mucinous neoplasms: Optimizing treatment strategies based on clinical, histological, and molecular...

Appendiceal mucinous neoplasms (AMNs) are rare tumors originating from mucin-producing epithelial cells of the appendix. They can exhibit both benign and malignant behavior. They are often incidentally discovered during appendectomy. Clinical presentation ranges from asymptomatic to mimicking acute appendicitis. Histologically, noninvasive AMNs are classified as low-grade AMNs (LAMNs) or high-grade AMNs (HAMNs), whereas invasive tumors are categorized as mucinous adenocarcinomas. Although LAMNs and HAMNs are generally nonmalignant, rupture can lead to pseudomyxoma peritonei (PMP). Surgical resection is the primary diagnostic and therapeutic approach, with intraoperative assessment to prevent rupture. Treatment strategies vary based on findings and include appendectomy, right hemicolectomy, and cytoreductive surgery with hyperthermic intraperitoneal chemotherapy. Histological diagnosis relies on mucin detection, and immunohistochemical markers such as cytokeratin 20 (diffusely positive), cytokeratin 7 (often negative), mucin 5AC, and special AT-rich sequence-binding protein 2 assist in characterization. Molecular profiling frequently identifies KRAS, GNAS, and TP53 mutations. KRAS mutations are generally associated with a favorable prognosis, whereas GNAS and TP53 mutations correlate with poorer survival outcomes. These findings highlight the potential role of molecular profiling in guiding treatment strategies for AMN and PMP.