Inside the rise of appendix cancer in under-50s as statistics show a dramatic increase in the number of young and middle-aged people being diagnosed

Few of us give much thought to our appendix unless it starts to ‘grumble’ – the non-medical term for swelling or pain.

This can potentially become full-blown appendicitis, which may require an operation to remove the 4in-long organ or risk a life-threatening rupture.

While the exact function of the appendix remains a mystery, it forms part of the digestive system and is connected to the bowel. But it has been drawing increasing attention globally because it has been linked to a rising tide of cancers – particularly in younger people.

Statistics show a dramatic increase in the number of under 50s diagnosed with appendix cancer, at a rate which is even outpacing other fast-growing diseases such as bowel cancer.

One study in the US last year found people aged between 29 and 44 were now the most likely to develop tumours in their appendix, with cases rising 71 per cent in just ten years. And the trend in the UK is strikingly similar.

Researchers from Bristol in 2022 found the incidence of appendix cancer increased a staggering five-fold in the 30 years from 1995 to 2016, with the biggest rises again found among those aged between 20 and 39.

While the cancer remains rare and overall numbers are reassuringly small – at just 1.6 cases for every 100,000 people in Britain – any increase should, as the Bristol researchers pointed out, be a ’cause for concern’.

Appendix cancer is not an easy disease to diagnose because it can progress without symptoms, or with vague symptoms such as mild abdominal pain and bloating. As a result, many cases are often picked up only after it has already spread and is harder to treat. Relapse is common, and around half of patients do not survive five years if diagnosed at this stage.

The gruelling treatment, which can involve extensive abdominal surgery as well as a procedure to bathe the abdomen in chemotherapy to kill off remaining cancer cells, can leave women infertile.

Professor Omer Aziz, who leads the appendix cancer unit at The Christie NHS Foundation Trust in Manchester, one of two national specialist centres which assess and treat the disease, says: ‘I am definitely seeing younger and younger people developing cancer.’

Tim Brill, a trustee of the appendix cancer charity Pseudomyxoma Survivor, described it as ‘a worrying trend’ and called for more research to drive early diagnosis and better treatments.

There is a lot scientists still do not understand about this rise and, frankly, about the appendix itself.

Situated in the lower right of the abdomen, it is thought to play a role in the gut’s immune system and in helping to clear waste from the body. A 2025 review published in the leading journal Nature emphasised how little is known about the causes of appendix cancer, branding it ‘an enigma’.

But there are some clues as to what may be driving some of the headline figures. And the good news is that those are, in the main, reassuring.

Ultimately, more early-stage cancers are being detected when people have surgery to remove their appendix, a procedure known as an appendectomy. These cancers tend to be the most common type to affect the appendix, and are known as neuroendocrine tumours, or NETs, which start in cells involved in hormones and signalling.

They tend to be small and slow growing, but once removed along with the appendix often need no further treatment.

Over the years the number of appendectomies has risen steadily, giving doctors more opportunities to find these previously hidden tumours. In England, for instance, 10,000 more such operations were carried out in 2016 compared with 1999.

And because people having their appendix removed are often relatively young, this may help explain some of the rise in diagnoses.

In parallel to this, the World Health Organisation (WHO) has changed the way such tumours are classified. Before 2000, they were often called carcinoids and were thought to be benign, or at least less aggressive. But research that suggested they could grow and become malignant meant that, from 2000 onwards, WHO guidelines introduced new terminology to describe them as NETs which meant, for the first time, they were recorded as cancer.

The result was an inevitable increase in the cancer statistics.

The Bristol study concluded the rising tide of UK diagnoses was being driven largely by an increase in the number of these NETs being picked up at grade one – the earliest cancer stage.

Professor Aziz says: ‘Previously, if a clinician saw something odd in an appendix when it was being removed it wouldn’t be investigated. Now it’s sent off to be studied. That is resulting in more cancers being diagnosed, and is certainly part of why we’re seeing figures suggesting a rise in the number of young people with the disease. The good news is that, with grade one NETs, no further treatment is needed once your appendix has been removed.’

But this is not the whole story.

Professor Amy Berrington, leader of the Clinical Cancer Epidemiology Group at The Institute of Cancer Research, says: ‘Some of this rise is due to a change in the way the disease is classified, but we are working to understand whether there are other causes along with the increase in colorectal [bowel] cancers.’

There has also been a rise – albeit not so steep – in the number of other tumours of the appendix which are not as well explained by better detection and classification changes.

The number of adenocarcinomas – tumours similar to those found in the bowel but which behave slightly differently – have trebled since 1995. And tumours known as pseudomyxoma peritonei, or PMP, which start in mucus-producing cells and can spread throughout the abdomen, have also risen by 2.5 times. Both remain extremely rare, with only a few hundred picked up every year.

But they tend to be found at a late stage, when they have already spread beyond the appendix.

PMP in particular requires gruelling treatment which is only carried out at The Christie and the other NHS specialist centre at Hampshire Hospitals NHS Foundation Trust.

It often involves removing the gallbladder, spleen, parts of the intestines and colon, the ovaries and uterus in women, as well as the appendix itself.

The abdominal cavity is then ‘washed’ with a heated chemotherapy treatment known as HIPEC to kill off remaining cancer cells. But there is a high chance it can come back.

At the moment there is no clear reason for there being a rise in either of those forms of appendix cancer, although experts suggest more CT scans are now carried out in A&E for abdominal pain and radiologists are better at identifying the disease.

Appendix cancer specialist Tom Cecil, clinical director of the NHS’s Peritoneal Malignancy Institute in Hampshire, says: ‘The key thing to remember is that this cancer is really rare. Even if the incidence increases, it remains rare. We’re treating more patients with it, young people, but also from all age groups.’

The broadest guess, he adds, is that something in the modern environment is driving the rise.

Research has found 11 forms of cancer are increasing in both younger people and in older age groups. The upsurge is particularly acute in young adults for appendix cancer, ovarian and bowel cancers.

Genetics may explain some of it. One 2022 study found that one in ten patients with appendix cancer carries a gene that makes them more likely to develop a form of cancer – although no single gene mutation has been linked specifically with appendix tumours.

There may be some links with colon cancers, some suggest. The gut microbiome – and, specifically, an imbalance in the type of bacteria which keeps it healthy – has been implicated in the development of bowel cancer.

Otherwise it’s likely that diet, lack of exercise, eating too much processed food and obesity may all be playing a role in fuelling our susceptibility to the disease – all factors which are known to influence other cancer types.

Professor Aziz says: ‘Research increasingly suggests the environment is affecting our genes in negative ways, and is making us more susceptible to cancer.’

Mr Cecil adds: ‘All the evidence suggests eating a balanced diet with few processed foods, maintaining a healthy weight, exercising regularly and not smoking or drinking too much, can reduce your risk of many diseases.’

I had to go through ‘the mother of all surgeries’

At just 40, Jonathan Pearcey was diagnosed with a rare form of appendix cancer after dismissing a grumbling pain in his abdomen and persistent bloating for several years.

The father-of-two, pictured with his wife Sarah, who lives just outside Preston, Lancashire, had the disease picked up when he had a CT scan following surgery for a hernia.

The condition, known as PMP, starts in the appendix and spreads throughout the abdominal cavity. He underwent ‘the mother of all surgeries’ at the specialist appendix cancer unit at The Christie NHS Foundation Trust in 2024 – a 12.5-hour operation which removed his spleen, appendix, gallbladder, abdominal lining, most of the large intestine and affected tissue around the liver, and was followed by chemotherapy.

‘Being diagnosed with a rare cancer aged 40, with two young boys, was a lot to take in,’ Jonathan said. ‘I look back now and think how bloated I was, and my weight was really high although we eat really well as a family.’

Jonathan, who runs a cheese business, has since been told the cancer has returned. ‘I’m focusing on looking after myself, being fit, being happy,’ he says. ‘I’d urge anyone not to ignore symptoms.’