The prostate is a small, walnut-sized gland that sits just below the bladder and in front of the rectum. It surrounds the urethra — the tube that carries urine and semen out of the body. The prostate's main job is to produce fluid that nourishes and protects sperm, making it an important part of the male reproductive system.

As men age, the prostate naturally grows larger. This is normal. But sometimes cells in the prostate begin to grow in an abnormal, uncontrolled way — and that is what we call prostate cancer.

Prostate cancer occurs when cells in the prostate gland mutate and begin to multiply without the normal controls that keep healthy cells in check. Over time, these abnormal cells can form a tumor.

The vast majority of prostate cancers — more than 95% — are a type called adenocarcinoma, meaning they start in the gland cells that produce prostate fluid. Other, rarer types exist but are much less common.

Prostate cancer is the most commonly diagnosed cancer in men in the United States (after skin cancer), and the second leading cause of cancer death in men. However, many prostate cancers grow very slowly and may never cause symptoms or require aggressive treatment during a man's lifetime.

Cancer develops through a process called carcinogenesis — a series of genetic changes that cause normal cells to behave abnormally. In the prostate, this process can take years or even decades before a tumor becomes detectable.

Risk factors that may increase the likelihood of prostate cancer include:

• Age: Risk increases significantly after age 50. Most prostate cancers are diagnosed in men over 65.
• Family history: Having a father or brother with prostate cancer more than doubles your risk.
• Race: African American men have a higher incidence and are more likely to be diagnosed at an advanced stage.
• Genetics: Inherited mutations in genes such as BRCA1, BRCA2, and others can increase risk.
• Diet and lifestyle: High-fat diets and obesity may play a role, though research is ongoing.

Prostate cancer often causes no symptoms in its early stages. It is most commonly detected through:

• PSA blood test: Prostate-Specific Antigen (PSA) is a protein produced by the prostate. Elevated PSA levels can signal cancer, though other conditions can also raise PSA.
• Digital rectal exam (DRE): A physician feels the prostate through the rectum to check for lumps or abnormal texture.
• Prostate biopsy: If PSA or DRE results are concerning, a biopsy is performed — small tissue samples are taken from the prostate and examined under a microscope.
• MRI: Multiparametric MRI is increasingly used before or alongside biopsy to identify suspicious areas in the prostate.

Receiving a prostate cancer diagnosis can feel overwhelming. But it is important to know that you have time to understand your options. Prostate cancer is rarely a medical emergency that requires immediate decisions.

Your care team will use several pieces of information to help you understand your cancer and discuss treatment options:

• Your PSA level
• Your Gleason score and Grade Group (how aggressive the cancer looks under a microscope)
• Your clinical stage (how far the cancer appears to have spread)
• Your biopsy results (how many cores were positive, percent involvement)
• Genomic test results, such as the Decipher score, in some cases

Each of these is covered in its own guide in this section. You do not need to understand everything at once — take it one topic at a time.