A " silent" cancer , often mistaken for less serious medical conditions , is causing concern. According to Cancer Research, there are approximately 10,300 new cases of bladder cancer in the UK each year. This equates to more than one diagnosis every hour, making bladder cancer the 11th most common cancer in the UK. The disease is known as "silent" because it often doesn't show symptoms until it has advanced . It occurs when a tumour, an abnormal growth of tissues, develops in the lining of the