The inside of the bladder is lined with many layers, each containing different types of cells. Sometimes, the cancer cells remain confined to the lining, not having grown into the deeper layers of the bladder. This is often called superficial bladder cancer, although it may also be referred to as noninvasive or non-muscle invasive. When cells have spread through the lining to other areas of the body it is referred to as invasive or muscle-invasive bladder cancer.
Urothelial carcinoma, also called transitional cell carcinoma (TCC), is the most common type of bladder cancer. It begins in the urothelial cells found in the innermost tissue layer of the bladder, ureters, and other areas within the urinary tract. About 90% of bladder cancers begin in these cells.
Less common types of bladder cancer include:
- Squamous cell carcinoma: Cancer that begins in squamous cells, which are thin, flat cells that may form in the bladder after long-term infection or irritation.
- Adenocarcinoma: Cancer that begins in glandular (secretory) cells that may form in the bladder after long-term irritation and inflammation.
- Sarcoma: Cancer that begins in the fat or muscle layers of the bladder wall.
- Small-cell carcinoma: A rare type of bladder cancer that begins in neuroendocrine cells. This type of bladder cancer is likely to spread to other parts of the body.
Your specific bladder cancer type will be diagnosed based upon the type of cell in which it began. There can also be a sub-type based on how the cancer cells are growing:
- Papillary carcinoma: the cancer cells grow in long, finger-like tumors starting from the inner layers of the bladder and growing towards the center, hollow area.
- Flat carcinoma: the cancer cells do not grow towards the center of the bladder.