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9 slides generated from the cancer page, with a quiz from the open benchmark and speaker notes that cite the sources. Arrow keys move between slides; Print gives one slide per page.
Low-grade appendiceal mucinous neoplasm is a slow-growing appendiceal cancer that makes mucus, and when it bursts it spreads jelly through the abdomen as pseudomyxoma peritonei. It rarely spreads through blood or lymph, so it is treated by stripping all visible disease from the abdomen and washing the cavity with heated chemotherapy, an operation that gives most patients many years of life.
Low-grade appendiceal mucinous neoplasms (LAMN) are villous or flat mucinous tumours that grow inside the appendix without invading its wall in the way a carcinoma does, distend it into a mucocele and, if they perforate, release mucin and tumour cells into the peritoneal cavity. There they redistribute along the flow of peritoneal fluid to the omentum, pelvis, right diaphragm and liver surface, producing pseudomyxoma peritonei, a slowly enlarging accumulation of mucin that eventually compresses the bowel and starves the patient. The PSOGI consensus of 2016 classifies the peritoneal disease as acellular mucin, low-grade, high-grade or high-grade with signet ring cells, and grade is the strongest predictor of survival; GNAS mutations are typical of low-grade disease, while TP53 and SMAD4 mark high-grade change. A LAMN confined to the appendix without perforation is cured by appendicectomy, and right hemicolectomy adds nothing.
Once the peritoneum is involved the treatment is cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC), developed by Paul Sugarbaker in the 1980s and 1990s: every visible deposit is removed by peritonectomy and organ resection, and the abdomen is then perfused with heated mitomycin (or oxaliplatin) for 60 to 90 minutes. A multi-institutional registry of 2,298 patients (Journal of Clinical Oncology 2012) reported a median survival of 16.3 years and 10-year survival of 63 percent after complete cytoreduction, and the operation is standard in specialist centres although it has never been compared with lesser surgery in a randomised trial. Systemic chemotherapy has little effect on low-grade disease, and a randomised trial at MD Anderson found no benefit from fluoropyrimidine-based chemotherapy over observation in unresectable low-grade mucinous adenocarcinoma, so it is kept for high-grade histology. Patients with recurrence can be operated again, and those with unresectable disease are managed by debulking for symptoms, and in trials by mucolytic agents such as bromelain with acetylcysteine and by pressurised intraperitoneal aerosol chemotherapy.
| Setting | Approach | Guideline |
|---|---|---|
| LAMN confined to the appendix | Appendicectomy with clear margin; no right hemicolectomy; surveillance imaging if mucin was found outside the appendix. | not mapped |
| Pseudomyxoma peritonei, resectable | Complete cytoreductive surgery (peritonectomy and organ resection) with hyperthermic intraperitoneal chemotherapy, mitomycin or oxaliplatin, in a specialist centre. | not mapped |
| High-grade pseudomyxoma peritonei | Cytoreductive surgery with HIPEC, with perioperative systemic chemotherapy (FOLFOX or CAPOX) as for appendiceal adenocarcinoma. | not mapped |
| Unresectable or recurrent disease | Repeat cytoreduction where feasible; debulking for symptoms; systemic chemotherapy only for high-grade histology; trials of mucolytics and pressurised intraperitoneal aerosol chemotherapy. | not mapped |