Gallbladder cancer is quite difficult to diagnose as it doesn't cause specific symptoms at the beginning. The gallbladder is a hidden organ, and cancer cells can grow in the region without being detected. However, there are some symptoms which indicate the initial stages of gallbladder cancer. Here are some of them: 
- Abdominal pain in the upper right corner
- Itchiness and bloating
- Fever and loss of appetite
- Yellowing of the skin and whites of the eyes
- Instant weight loss
As you can see, these symptoms are common to many other illnesses. Hence, it is important to consult your doctor immediately if you are suffering from any of the aforementioned symptoms. Your doctor is the best person to diagnose the condition.