Urinary Bladder is a hollow bag located in the pelvis, that collects and stores the urine from kidneys. When the normal body cells multiply, they form an abnormal area of cells, called tumour.
Bladder cancer is classified by how deeply they invade the bladder wall. Superficial bladder cancer is limited to innermost lining of the bladder. Invasive bladder cancer is the one which has penetrated the muscular layer of the bladder wall.
Along with classification, the grade of the tumour is based on the degree of abnormality of the tumour. Low grade tumors are less aggressive whereas high grade tumours are dangerous.