What is prostate cancer? -

What is prostate cancer?
Prostate cancer starts in the cells of the prostate. A cancerous (malignant) tumour is a group of cancer cells that can grow into and destroy nearby tissue. It can also spread (metastasize) to other parts of the body. Prostate cancer is the most common cancer in Canadian men. Many older men have this disease without knowing it. It usually grows slowly and can often be completely removed or successfully managed when it is diagnosed. Older men with prostate cancer often die of other causes.

The prostate is part of a man’s reproductive and urinary systems. It is a walnut-sized gland just below the bladder and in front of the rectum. It surrounds part of the urethra, which is the tube that carries urine and semen through the penis. The prostate makes mucus and prostatic fluid, which mix with sperm and other fluids to make semen.

Cells in the prostate sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous (benign) conditions such as prostatitis and benign prostatic hyperplasia (BPH).

Changes to prostate cells can also cause precancerous conditions. This means that the abnormal cells are not yet cancer, but there is a chance they will become cancer if they aren’t treated. Precancerous conditions that can develop in the prostate are prostatic intraepithelial neoplasia (PIN), atypical small acinar proliferation (ASAP) and proliferative inflammatory atrophy (PIA).

But in some cases, changes to prostate cells can cause prostate cancer. Most often, prostate cancer starts in gland cells of the prostate. This type of cancer is called adenocarcinoma of the prostate.

Rare types of prostate cancer can also develop. These include urothelial carcinoma (also called transitional cell carcinoma), sarcoma and small cell carcinoma.

The prostate
The prostate (or prostate gland) is part of a man’s reproductive and urinary systems. It is about the size of a walnut in younger men, but it starts to get larger when men reach their late 40s and early 50s.

The prostate is deep inside a man’s pelvis, below the bladder and in front of the rectum. It wraps around the upper part of the urethra (called the prostatic urethra). The urethra is a tube that carries urine from the bladder, through the prostate and penis, and out of the body.

The prostate is close to parts of the digestive, urinary and reproductive systems. As a result, prostate cancer and its treatments can affect these systems. For example, an enlarged prostate can press on and block the urethra, which can cause problems urinating. Radiation therapy for prostate cancer can affect the rectum and cause bowel problems. Surgery to remove prostate cancer can affect nerves that supply the bladder and penis, which can affect urinary and sexual function.

Male Reproductive System

Structure
The upper part of the prostate is called the base. It rests against the lower part (neck) of the bladder. The lower, narrowed part of the prostate is called the apex. The prostate is divided into a right and a left lobe.

The prostate is made up of many branching ducts surrounded by the stroma. The stroma is made up of connective tissue and muscle fibres. The cells that line the ducts make prostatic fluid, which is mixed with sperm and other fluid to make semen. Most of the prostate is covered by a thin layer of connective tissue called the capsule. The apex of the prostate is covered by the anterior fibromuscular stroma, which is made up of muscle fibres and connective tissue.

The seminal vesicles are glands found on each side of the prostate. They make most of the fluid in semen. The seminal vesicles are sometimes removed during surgery to remove the prostate (called a radical prostatectomy).

Diagram of the prostate zones

The prostate is divided into the following areas.

The peripheral zone is the largest area of the prostate. It can easily be felt by the doctor during a digital rectal exam (DRE). Most prostate cancers start in the peripheral zone.

The transition zone surrounds the part of the urethra that passes through the prostate (called the prostatic urethra). This zone gets bigger as men age, a condition called benign prostatic hyperplasia (BPH).

The central zone lies behind the transition zone and surrounds the ejaculatory ducts, which run from the seminal vesicles to the prostatic urethra. Very few prostate cancers start in the central zone.

The anterior fibromuscular stroma is a thickened area of tissue that surrounds the apex of the prostate. It is made of muscle fibres and fibrous connective tissue. This area of the prostate doesn’t contain any glands. Prostate cancer is rarely found in this part of the prostate.

Function
The main function of the prostate is to make prostatic fluid. Prostatic fluid is rich in enzymes, proteins and minerals that help protect and nourish sperm. When a man is sexually aroused, the prostate pushes prostatic fluid through the ducts and into the urethra. Prostatic fluid mixes with sperm and other fluids in the urethra and is ejaculated as semen.

Hormones, including testosterone and those made by the pituitary gland and adrenal glands, help control the function of the prostate gland

Cancerous tumours of the prostate
A cancerous tumour of the prostate can grow into and destroy nearby tissue. It can also spread (metastasize) to other parts of the body. Cancerous tumours are also called malignant tumours.

Adenocarcinoma
Adenocarcinoma of the prostate is the most common type of prostate cancer. It accounts for 95% of all prostate cancers.

Adenocarcinoma starts in gland cells. Gland cells in the prostate make mucus and prostatic fluid, which mix with sperm and other fluids to make semen. Most adenocarcinomas are found in the outer part of the prostate, which is called the peripheral zone. Doctors can often feel a cancer in the peripheral zone during a digital rectal exam (DRE).

Adenocarcinoma usually develops in more than one area (site) of the prostate. When cancer is found in more than one area of an organ it is called multifocal cancer. Each site in the prostate can have a different grade.

Rare cancerous tumours of the prostate
The following cancerous tumours of the prostate are rare:

urothelial carcinoma (also called transitional cell carcinoma)
sarcoma
small cell carcinoma
carcinoid tumours
squamous cell carcinoma


Read more: http://www.cancer.ca/en/cancer-information/cancer-type/prostate/prostate-cancer/cancerous-tumours/?region=on#ixzz56ISQY6Gg