1. Abdominal pain or discomfort
Pain, especially in the right upper quadrant area; this is usually caused by an enlarged liver. However, pain can occur anywhere in abdomen depending upon the site of the origin of the tumour. For example, Stomach tumour can cause pain in epigastrium, small bowel tumour can cause pain around umbilicus & colonic tumour cause pain in lower abdomen.

2. A change in bowel habits
Constipation or diarrhoea, can be due to changes in diet, medications, stress, etc., but it could also mean there’s something wrong with your digestive system, especially tumour in the large bowel (colon). Screening for colonoscopy is recommended every 10 years for people above the age of 60 years, so that the tumours can be detected in early stage & treated effectively.

3. Weight loss
Weight loss without trying hard enough to lose weight. If you have lost more than 10% of your body weight over 6 months, call your doctor for advice. Your clothes will start to feel loose if you have lost 2-3 kg of weight.

4. Blood in stool or vomit. 
Blood in stool can make the stool appear black, which is a common presenting feature of stomach & small intestinal cancer. Fresh blood (red colour) in stool is most commonly caused by piles or fissure (not a cancer), however, a tumour in large intestine can also present with the same complaint. Blood in stool when associated with change in bowel habits (constipation of diarrhoea) should not be neglected.

5. Persistent nausea or vomiting.
They are most commonly caused by a minor infection in digestive tract(called gastroenteritis), however, if it lasts for more than a month, than one should consult a gastroenterologist to rule out possibility of pathology in upper part of digestive system mainly stomach & duodenum.

6. Reduced appetite.
Not having sufficient appetite for food is also suggestive of some systemic illness. This is usually seen with liver diseases e.g. hepatitis. However, if this is lasting for a longer period & affecting your health, you should consult a doctor.

7. Jaundice
Commonest cause of jaundice is viral hepatitis (an infection of liver by a virus). However, one should consult the doctor when jaundice lasts longer than 10 days to rule out tumours in liver, gallbladder, bile duct & pancreas. This can be easily diagnosed with an ultrasound abdomen.

8. Bloating or swelling around the abdomen.
Abdominal swelling is very common in obese individuals. Swelling also occurs when fluid collects inside abdomen. It can also occur with distension of intestines. Last two scenarios require further investigations to rule out tumours in the abdomen.