Appendiceal neuroendocrine cancer (also called appendiceal neuroendocrine tumours or aNETs) is a rare type of neuroendocrine tumour (NET) that develops in the appendix.
These tumours are typically:
In fact, most cases are discovered after the appendix has already been removed.
Appendiceal NETs are the most common tumour of the appendix, and the outlook is generally very good, particularly when detected early. However, this condition can cause complications if not treated in a timely manner.
Appendiceal NETs arise from neuroendocrine cells, which receive signals from the nervous system and respond by producing hormones and other chemical messengers that help regulate essential body functions.
Localisation of tumour (tip, base or close to the base) has to be reported. The most common location is the tip (51%–86%), rarely the base (3%–11%).
This location means they often don’t block the appendix, which is why they are usually found by chance.
Appendiceal neuroendocrine cancers are sometimes found by accident during surgery for appendicitis. In many cases, there are no clear symptoms beforehand.
This incidental diagnosis is actually a positive outcome. It means the tumour is usually:
Because of this, many patients require no further treatment beyond appendectomy.
However, once diagnosed, it’s important to review the pathology carefully to confirm risk level.
Even when found early, appropriate follow-up ensures that any rare cases of spread or recurrence are identified and managed quickly.
Most people have no symptoms before diagnosis. But when symptoms do occur, they often mimic appendicitis.
Here are some key characteristics to look out for:
In very rare cases, if the cancer has spread (especially to the liver) or if there is another coexisting primary NET (for example, in the small bowel), patients may develop carcinoid syndrome, including:
Most cases are diagnosed after an appendectomy, when the removed appendix is examined under a microscope. It can also be diagnosed during abdominal surgery performed for unrelated reasons.
For larger or higher-risk tumours, or those exhibiting symptoms suggestive of carcinoid syndrome:
Tumour size is the most important factor in determining treatment.
For appendiceal NETs, size isn’t the only thing that matters. After surgery, the tumour is assessed for features that affect risk.
Key factors include:
If higher-risk features are present, further surgery or closer follow-up may be recommended.
Appendectomy
Right hemicolectomy
After treatment, follow-up depends on tumour size and risk.
For low-risk tumours (for example, less than 1 cm with no spread):
For higher-risk tumours:
The goal is to detect any recurrence early and manage long-term risk appropriately.
Appendiceal NETs generally have an excellent prognosis.
Because most tumours are found early, many patients are cured with surgery alone.
While most appendiceal NETs are low grade, there are rarer types that behave differently:
For many patients, treatment is straightforward, but follow-up care is still important.
Being diagnosed unexpectedly after appendicitis can be confronting. Support and clear guidance are important.
Appendiceal NETs fall within gastroenteropancreatic NETs (GEP-NETs).
They share key features with other NETs:
Even when prognosis is excellent, a NET diagnosis can feel uncertain.
NECA provides:
Speaking with a NET specialist nurse can help clarify next steps and provide reassurance.
If you’ve been diagnosed with an appendiceal neuroendocrine tumour:
For guidance and support, contact the NECA NET Nurse.
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