{"entity":{"id":"low-grade-appendiceal-mucinous-neoplasm","kind":"cancer","name":"Low-grade appendiceal mucinous neoplasm and pseudomyxoma peritonei","aka":["LAMN","Pseudomyxoma peritonei","PMP","Low-grade mucinous carcinoma peritonei","Disseminated peritoneal adenomucinosis","Jelly belly"],"tldr":"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.","summary":"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.\n\nOnce 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.","asOf":"2026-09-18","wikipedia":"https://en.wikipedia.org/wiki/Pseudomyxoma_peritonei","links":[{"label":"PMP registry (JCO 2012)","url":"https://doi.org/10.1200/JCO.2011.39.7166"},{"label":"PSOGI classification (Am J Surg Pathol 2016)","url":"https://doi.org/10.1097/PAS.0000000000000535"},{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Pseudomyxoma_peritonei"}],"tags":["subtype-page","gastrointestinal"],"related":["appendiceal-adenocarcinoma","goblet-cell-adenocarcinoma","appendiceal","peritoneal-mesothelioma"],"cancers":[],"sections":[],"technologies":["hipec","hipec-pipac-devices","ct","mri"],"targets":["kras"],"drugs":["mitomycin","folfox","capox"],"companies":[],"institutions":[],"pathways":[],"terms":["hipec-procedure","peritoneal-metastasis","debulking","colectomy","peritoneum"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":["paper-psogi-pseudomyxoma-appendiceal-classification-am-j-surg-pathol-2016","paper-who-2019-digestive-system-tumours-nagtegaal-histopathology-2020"],"journals":[],"dependsOn":[],"notes":[],"group":"gastrointestinal","burden":"The commonest appendiceal neoplasm; most low-grade mucinous neoplasms are cured by appendicectomy, and the minority that rupture and seed the abdomen with mucin cause pseudomyxoma peritonei, which affects only a few people per million each year.","subtypes":["Low-grade appendiceal mucinous neoplasm confined to the appendix (cured by appendicectomy)","LAMN with acellular mucin outside the appendix (low recurrence risk, surveillance)","Low-grade pseudomyxoma peritonei (low-grade mucinous carcinoma peritonei)","High-grade appendiceal mucinous neoplasm (HAMN) and high-grade pseudomyxoma peritonei","Pseudomyxoma peritonei with signet ring cells (worst grade)","Recurrent pseudomyxoma peritonei after cytoreductive surgery"],"biomarkers":["PSOGI grade of the peritoneal disease (acellular, low, high, signet ring)","Peritoneal cancer index (extent) and completeness of cytoreduction score","GNAS mutation (low grade), KRAS; TP53 and SMAD4 (high grade)","CEA, CA 19-9 and CA-125 (prognosis and surveillance)","Perforation and extra-appendiceal mucin on the appendicectomy specimen"],"standardOfCare":[{"setting":"LAMN confined to the appendix","approach":"Appendicectomy with clear margin; no right hemicolectomy; surveillance imaging if mucin was found outside the appendix.","refs":["colectomy","ct"],"guideline":{"version":"NCCN Guidelines: Colon Cancer (appendiceal section)","url":"https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1428"}},{"setting":"Pseudomyxoma peritonei, resectable","approach":"Complete cytoreductive surgery (peritonectomy and organ resection) with hyperthermic intraperitoneal chemotherapy, mitomycin or oxaliplatin, in a specialist centre.","refs":["hipec","hipec-procedure","mitomycin","peritoneal-metastasis","debulking"],"guideline":{"version":"NCCN Guidelines: Colon Cancer (appendiceal section)","url":"https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1428"}},{"setting":"High-grade pseudomyxoma peritonei","approach":"Cytoreductive surgery with HIPEC, with perioperative systemic chemotherapy (FOLFOX or CAPOX) as for appendiceal adenocarcinoma.","refs":["hipec","folfox","capox"],"guideline":{"version":"NCCN Guidelines: Colon Cancer (appendiceal section)","url":"https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1428"}},{"setting":"Unresectable or recurrent disease","approach":"Repeat cytoreduction where feasible; debulking for symptoms; systemic chemotherapy only for high-grade histology; trials of mucolytics and pressurised intraperitoneal aerosol chemotherapy.","refs":["debulking","hipec-pipac-devices","folfox"],"guideline":{"version":"NCCN Guidelines: Colon Cancer (appendiceal section)","url":"https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1428"}}],"stateOfArt":["Cytoreductive surgery with HIPEC gives long survival in low-grade pseudomyxoma peritonei and is the model for peritoneal surface oncology.","The PSOGI classification made grade the basis of treatment decisions across centres.","Chemotherapy has no proven role in low-grade disease, sparing patients its toxicity."],"history":[{"year":1884,"title":"Werth coins the term pseudomyxoma peritonei","refs":[]},{"year":1995,"title":"Sugarbaker describes peritonectomy procedures and heated intraperitoneal chemotherapy","refs":["hipec","hipec-procedure"]},{"year":2012,"title":"International registry of 2,298 patients: median survival 16.3 years after cytoreduction and HIPEC","refs":["hipec"]},{"year":2016,"title":"PSOGI consensus classification of appendiceal mucinous neoplasms and pseudomyxoma peritonei","refs":[]},{"year":2023,"title":"Randomised trial finds no benefit from systemic chemotherapy in unresectable low-grade mucinous appendiceal adenocarcinoma","refs":["folfox"]}],"pipeline":["hipec","hipec-pipac-devices"],"openProblems":["Cytoreduction with HIPEC has never been compared with cytoreduction alone in this disease.","Recurrence after complete cytoreduction is common and criteria for reoperation vary.","No effective systemic therapy exists for low-grade disease.","Patients are often diagnosed late after years of abdominal distension."],"parent":"appendiceal"},"route":"/cancers/low-grade-appendiceal-mucinous-neoplasm/","neighbours":{"cancer":[{"id":"appendiceal-adenocarcinoma","kind":"cancer","name":"Appendiceal adenocarcinoma (mucinous and non-mucinous, including signet ring cell)","route":"/cancers/appendiceal-adenocarcinoma/"},{"id":"appendiceal","kind":"cancer","name":"Appendiceal cancer and pseudomyxoma peritonei","route":"/cancers/appendiceal/"},{"id":"goblet-cell-adenocarcinoma","kind":"cancer","name":"Goblet cell adenocarcinoma of the appendix","route":"/cancers/goblet-cell-adenocarcinoma/"},{"id":"peritoneal-mesothelioma","kind":"cancer","name":"Peritoneal mesothelioma","route":"/cancers/peritoneal-mesothelioma/"}],"technology":[{"id":"ct","kind":"technology","name":"CT (computed tomography)","route":"/technologies/ct/"},{"id":"hipec","kind":"technology","name":"HIPEC / PIPAC (intraperitoneal chemotherapy)","route":"/technologies/hipec/"},{"id":"hipec-pipac-devices","kind":"technology","name":"HIPEC perfusion pumps and PIPAC nebulisers","route":"/technologies/hipec-pipac-devices/"},{"id":"mri","kind":"technology","name":"MRI","route":"/technologies/mri/"}],"target":[{"id":"kras","kind":"target","name":"KRAS","route":"/targets/kras/"}],"drug":[{"id":"capox","kind":"drug","name":"CAPOX (capecitabine, oxaliplatin)","route":"/drugs/capox/"},{"id":"folfox","kind":"drug","name":"FOLFOX (5-FU, leucovorin, oxaliplatin)","route":"/drugs/folfox/"},{"id":"mitomycin","kind":"drug","name":"Mitomycin C","route":"/drugs/mitomycin/"}],"term":[{"id":"colectomy","kind":"term","name":"Colectomy","route":"/terms/colectomy/"},{"id":"debulking","kind":"term","name":"Debulking (cytoreductive surgery)","route":"/terms/debulking/"},{"id":"hipec-procedure","kind":"term","name":"HIPEC (hyperthermic intraperitoneal chemotherapy)","route":"/terms/hipec-procedure/"},{"id":"peritoneal-metastasis","kind":"term","name":"Peritoneal metastasis","route":"/terms/peritoneal-metastasis/"},{"id":"peritoneum","kind":"term","name":"Peritoneum and peritoneal metastases","route":"/terms/peritoneum/"}],"paper":[{"id":"paper-psogi-pseudomyxoma-appendiceal-classification-am-j-surg-pathol-2016","kind":"paper","name":"PSOGI consensus for classification and pathological reporting of pseudomyxoma peritonei and associated appendiceal neoplasia","route":"/key-papers/paper-psogi-pseudomyxoma-appendiceal-classification-am-j-surg-pathol-2016/"},{"id":"paper-who-2019-digestive-system-tumours-nagtegaal-histopathology-2020","kind":"paper","name":"The 2019 WHO classification of tumours of the digestive system","route":"/key-papers/paper-who-2019-digestive-system-tumours-nagtegaal-histopathology-2020/"}]}}