The symptoms of neuroendocrine cancer depend on where the tumour develops in the body. If the tumour is growing slowly and not making too much hormone, it might not cause any symptoms. Symptoms might occur later as the tumour grows (if it is a functional tumour). 

A summary of possible symptoms of different types of neuroendocrine tumours (NETs) is as follows: 

• intestinal NETs 
   - watery diarrhoea 
   - nausea and vomiting 
   - abdominal pain 
   - constipation 
   - bowel obstruction 
   - bleeding from the rectum 
   - anaemia 
   - indigestion 
   - flushing 
   - wheezing 
   - jaundice 
   - fatigue 
   - weight loss 
• lung NETs 
   - wheezing 
   - cough 
   - coughing up blood 
   - difficulty breathing 
   - fatigue 
   - recurrent chest infections 
• pancreatic NETs 
   - back pain 
   - peptic ulcer disease 
   - diarrhoea 
   - low or high blood sugar 
   - diabetes 
   - weight loss 
   - jaundice 
   - rash. 

A group of symptoms called carcinoid syndrome may occur with any type of NET. Carcinoid syndrome results from a NET releasing large amounts of the hormone serotonin. 

Symptoms of carcinoid syndrome include: 

• flushing of the skin, especially the face and neck 
• diarrhoea 
• wheezing 
• abdominal pain 
• fast or irregular heartbeat 
• fatigue 
• low blood pressure 
• heart damage. 

Another syndrome that can develop in people with NETs is Cushing syndrome, when the adrenal glands make too much of the hormone cortisol. 

Symptoms of Cushing syndrome include: 

• weight gain 
• a red, round, full face 
• muscle weakness 
• increased growth of hair on the face and body 
• high blood pressure 
• high blood sugar 
• changes in mood and behaviour. 

There are a number of conditions that may cause the same symptoms as neuroendocrine cancer. If any of these symptoms are experienced, it is important that they are discussed with a doctor.