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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.
Averages across everyone diagnosed, often years ago. A median is the middle of a group: half the people counted lived longer than the figure shown, and some lived far longer. Your stage, subtype, age, fitness and the treatment you receive matter more than the average, and the numbers are improving quickly.
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.
Right-sided tumours behave differently from left-sided and rectal ones; the colon drains along its mesenteric vessels, the rectum into the mesorectum and pelvic side wall.
Same organ: Colon cancer (adenocarcinoma of the colon), Micropapillary adenocarcinoma of the colon and rectum, Adenoma-like adenocarcinoma of the colon and rectum, Lynch syndrome-associated colorectal cancer, Familial adenomatous polyposis-associated colorectal cancer, Mucinous adenocarcinoma of the colon and rectum, Signet ring cell carcinoma of the colon and rectum, Medullary carcinoma of the colon, Serrated adenocarcinoma of the colon and rectum, Peritoneal mesothelioma, Colorectal cancer, Rectal cancer, Mismatch-repair deficient (MSI-high) colorectal cancer, BRAF V600E-mutant colorectal cancer, HER2-amplified colorectal cancer, KRAS G12C-mutant colorectal cancer, Early-onset colorectal cancer (under 50), Anal cancer (squamous cell carcinoma), Appendiceal cancer and pseudomyxoma peritonei, Small intestine cancer (small bowel adenocarcinoma), Small intestinal neuroendocrine tumours, Anal high-grade squamous intraepithelial lesions (precursor), Localised anal squamous cell carcinoma (stage I to III), Metastatic and recurrent anal squamous cell carcinoma, Appendiceal adenocarcinoma (mucinous and non-mucinous, including signet ring cell), Goblet cell adenocarcinoma of the appendix, Localised small bowel adenocarcinoma (stage I to III, resected), Advanced and metastatic small bowel adenocarcinoma
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Also on OnCo: Symptoms and red flags · Early detection roadmap.
Appendicectomy with clear margin; no right hemicolectomy; surveillance imaging if mucin was found outside the appendix.
Complete cytoreductive surgery (peritonectomy and organ resection) with hyperthermic intraperitoneal chemotherapy, mitomycin or oxaliplatin, in a specialist centre.
Cytoreductive surgery with HIPEC, with perioperative systemic chemotherapy (FOLFOX or CAPOX) as for appendiceal adenocarcinoma.
Repeat cytoreduction where feasible; debulking for symptoms; systemic chemotherapy only for high-grade histology; trials of mucolytics and pressurised intraperitoneal aerosol chemotherapy.
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The names on an appendix or small bowel pathology report, and hence which OnCo subtype page applies, follow this classification.
Whether an appendiceal tumour is called LAMN or adenocarcinoma, and whether peritoneal disease is graded low or high, decides prognosis and treatment; this paper set those names.
One cancer page on OnCo cites this paper by its DOI; this record gives the citation a page of its own so a reader can follow it without leaving OnCo. Read the abstract above alongside the citing page listed under Related; the record was created automatically from the Europe PMC entry and its figures have not been checked by hand.
Query for this cancer: (TITLE:"Low-grade appendiceal mucinous neoplasm and pseudomyxoma peritonei" OR ABSTRACT:"Low-grade appendiceal mucinous neoplasm and pseudomyxoma peritonei" OR TITLE:"LAMN" OR ABSTRACT:"LAMN" OR TITLE:"Pseudomyxoma peritonei" OR ABSTRACT:"Pseudomyxoma peritonei" OR TITLE:"PMP" OR ABSTRACT:"PMP" OR TITLE:"Low-grade mucinous carcinoma peritonei" OR ABSTRACT:"Low-grade mucinous carcinoma peritonei" OR TITLE:"Disseminated peritoneal adenomucinosis" OR ABSTRACT:"Disseminated peritoneal adenomucinosis") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Low-grade appendiceal mucinous neoplasm and pseudomyxoma peritonei, not a curated reading list.
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Bleeding that does not stop by itself, bleeding from more than one site, or new bruising in several places or one large area.
The bowel cancer regimens share low blood counts, tiredness, sickness and a sore mouth. Oxaliplatin adds cold-triggered tingling, irinotecan adds early and late diarrhoea, capecitabine adds hand-foot syndrome and needs a DPD test first, and cetuximab or panitumumab add an acne-like rash and low magnesium. The rule for all of them: ring the 24-hour number rather than wait.
See all on the product pages:CAPOX (capecitabine, oxaliplatin)FOLFOX (5-FU, leucovorin, oxaliplatin)Mitomycin C·Printable cards in the navigator
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