Introduction to Bladder Cancer

Bladder Cancer Subtypes

A basic understanding of the terminology used by doctors to describe the various subtypes of bladder tumors is important in order to more fully appreciate the various approaches to treatment, the treatment options, and the prognosis (chances for recovery).

Superficial bladder tumors are those that are localized (confined) to the transitional epithelium (urothelium) - the layer of epithelial cells that lines the inside of the bladder wall and is in direct contact with the urine - but have not spread to the deeper layers of the bladder. Additionally, bladder tumors that have invaded the lamina propria but have not invaded the muscularis propria can be considered as superficial.

Invasive bladder cancer refers to a bladder tumor that is either invading the muscularis propria - the deeper layer of muscle cells that forms the wall of the bladder - or the perivesical fat located beyond the bladder muscle. This type of tumor is referred to as muscle-invasive bladder cancer. Muscle-invasive bladder cancer carries a higher risk of spreading beyond the bladder (metastases) and must be treated more aggressively than superficial bladder cancer. The term metastatic bladder cancer is used when the cancer cells have spread beyond the bladder to distant sites.

Another important characteristic of bladder tumors that is useful in classification of the various subtypes is the morphology (appearance) of the cells under a microscope. In general, the shape of individual bladder cancer cells can be either papillary (cells that have thin, finger-like projections) or flat (no projections). Papillary and flat bladder tumor cells can be further subdivided into noninvasive or invasive types depending upon their pattern of growth within the bladder. Non-invasive, flat bladder tumors invading the lamina propria are also referred to as carcinoma in situ.