# Appendiceal cancer and pseudomyxoma peritonei

Source: https://onco.cc/cancers/appendiceal/  
OnCo record `appendiceal` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Rare tumours of the appendix that range from slow mucin-producing growths that fill the abdomen (pseudomyxoma peritonei) to aggressive adenocarcinomas. The slow forms are treated by extensive surgery with heated chemotherapy in the abdomen; the fast ones like colon cancer.

## Summary

Appendiceal neoplasms include low-grade appendiceal mucinous neoplasms (LAMN) that rupture and seed the peritoneum as pseudomyxoma peritonei (PMP), mucinous and non-mucinous adenocarcinomas, goblet cell adenocarcinoma, and neuroendocrine tumours (the most common appendix tumour, usually cured by appendicectomy). PSOGI grading (acellular mucin, low-grade, high-grade, signet ring) predicts outcome. GNAS mutations mark low-grade mucinous disease; KRAS, TP53 and SMAD4 mark higher grade.

For PMP and peritoneal disease, cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC, usually mitomycin C) at an experienced centre gives 10-year survival of ~60-70% for low-grade disease (Sugarbaker, Chua 2012). Systemic chemotherapy (FOLFOX/CAPOX) is used for high-grade and unresectable disease but a randomised trial (2024) showed no benefit in low-grade mucinous carcinoma peritonei. Iterative CRS, mucolytics (bromelain-acetylcysteine) and intraperitoneal therapies are under study. Appendiceal adenocarcinoma is otherwise managed like colorectal cancer, with right hemicolectomy and stage-based chemotherapy.

## Fields

- Kind: Cancer
- Last checked: 2026-09-08
- Also known as: Appendix cancer; PMP; Low-grade appendiceal mucinous neoplasm (LAMN)
- Tags: gap-fill; gastrointestinal; rare
- Group: gastrointestinal
- Burden: About 1-2 per 100,000 per year and rising, especially in adults under 50; most are found incidentally at appendicectomy.
- Subtypes: LAMN / HAMN (low- and high-grade appendiceal mucinous neoplasm); Pseudomyxoma peritonei (low- vs high-grade, PSOGI); Mucinous and non-mucinous adenocarcinoma; Goblet cell adenocarcinoma; Signet ring cell carcinoma; Appendiceal neuroendocrine tumour
- Biomarkers: PSOGI histologic grade; Peritoneal cancer index (PCI) and completeness of cytoreduction (CC score); GNAS (low-grade), KRAS, TP53, SMAD4; CEA, CA19-9, CA-125; MSI (rare)

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/appendiceal/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/appendiceal/#overview [3 subtypes, 3 state-of-the-art points]
- What it is (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/appendiceal/#what-it-is [9 subtypes]
- Finding it (on the hub): How it shows itself, how it is confirmed, what screening exists, and the biomarkers clinicians test for. https://onco.cc/cancers/appendiceal/#finding-it [5 biomarkers]
- Treating it (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/appendiceal/#treating-it [3 settings, 2 decisions with options]
- Evidence (on the hub): Trials recruiting now, the landmark trials, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/appendiceal/#evidence [1 trial, 6 milestones]
- The science (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/appendiceal/#science [3 targets, 1 pathway]
- Where you are (own page): Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record. https://onco.cc/cancers/appendiceal/where-you-are/
- Living with it (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/appendiceal/#living-with-it [14 questions, 5 red cards]
- What is coming (own page): Everything in development, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/appendiceal/coming/ [5 medicines, 1 trial, 4 open problems]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/appendiceal/data/ [29 connected records]

## Standard of care

- Localised LAMN / adenocarcinoma: Appendicectomy (LAMN without perforation) or right hemicolectomy (adenocarcinoma, goblet cell); adjuvant chemotherapy for node-positive adenocarcinoma by colorectal analogy. ([FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/), [CAPOX (capecitabine, oxaliplatin)](https://onco.cc/drugs/capox/))
- Pseudomyxoma peritonei / peritoneal disease: Cytoreductive surgery with HIPEC at a peritoneal-surface-malignancy centre; repeat CRS for recurrence when feasible. ([HIPEC / PIPAC (intraperitoneal chemotherapy)](https://onco.cc/technologies/hipec/))
- High-grade or unresectable peritoneal disease: FOLFOX/CAPOX ± bevacizumab; systemic chemotherapy has no proven benefit in low-grade disease (randomised 2024). ([FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/), [CAPOX (capecitabine, oxaliplatin)](https://onco.cc/drugs/capox/), [Bevacizumab](https://onco.cc/drugs/bevacizumab/))

## State of the art

- CRS-HIPEC turned PMP from a disease with no effective treatment into one with long survival for low-grade histology.
- Grade, not stage, drives therapy: the 2024 randomised trial ended routine chemotherapy for low-grade mucinous carcinomatosis.
- Molecular profiling (GNAS vs KRAS/TP53) is beginning to formalise the low/high grade split.

## Open problems

- No effective systemic therapy for high-grade or signet-ring disease.
- Selection for CRS-HIPEC and management of recurrence after maximal surgery.
- Rising incidence in young adults is unexplained.
- Centralisation: outcomes depend heavily on centre experience.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Pseudomyxoma_peritonei
- PSOGI consensus (Am J Surg Pathol 2016): https://doi.org/10.1097/PAS.0000000000000535
- Appendix Cancer / PMP Research Foundation: https://www.acpmp.org/

## Connected records

- technologies: [CEA surveillance after colorectal cancer surgery](https://onco.cc/technologies/cea-surveillance-colorectal/), [CT (computed tomography)](https://onco.cc/technologies/ct/), [Cytotoxic chemotherapy](https://onco.cc/technologies/cytotoxic-chemotherapy/), [HIPEC / PIPAC (intraperitoneal chemotherapy)](https://onco.cc/technologies/hipec/), [HIPEC perfusion pumps and PIPAC nebulisers](https://onco.cc/technologies/hipec-pipac-devices/), [MRI](https://onco.cc/technologies/mri/)
- targets: [KRAS](https://onco.cc/targets/kras/), [TP53](https://onco.cc/targets/tp53/)
- drugs: [Bevacizumab](https://onco.cc/drugs/bevacizumab/), [CAPOX (capecitabine, oxaliplatin)](https://onco.cc/drugs/capox/), [FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/), [Mitomycin C](https://onco.cc/drugs/mitomycin/), [Oxaliplatin](https://onco.cc/drugs/oxaliplatin/)
- pathways: [RAS / RAF / MEK / ERK (MAPK)](https://onco.cc/pathways/ras-mapk/)
- terms: [Colectomy](https://onco.cc/terms/colectomy/), [Peritoneal metastasis](https://onco.cc/terms/peritoneal-metastasis/), [Rare cancers](https://onco.cc/terms/rare-cancers/)
- companies: [Belmont Medical Technologies](https://onco.cc/companies/belmont-medical-technologies/)
- cancers: [Appendiceal adenocarcinoma (mucinous and non-mucinous, including signet ring cell)](https://onco.cc/cancers/appendiceal-adenocarcinoma/), [Goblet cell adenocarcinoma of the appendix](https://onco.cc/cancers/goblet-cell-adenocarcinoma/), [Low-grade appendiceal mucinous neoplasm and pseudomyxoma peritonei](https://onco.cc/cancers/low-grade-appendiceal-mucinous-neoplasm/)
- trials: [A Study to Investigate APL-5125 in Adults With Advanced Solid Tumors](https://onco.cc/trials/nct06399757/)

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JSON: https://onco.cc/api/v1/entities/appendiceal.json