Cell growth is well-regulated in the normal prostate gland, as in most body organs. While aged cells die (apoptosis), new cells are created retaining the function of the old ones. In the setting of cancer, regulation is missing. Cells proliferate out of normal control resulting in many accumulating genetic errors.
As e result, most cells seize to perform their normal function. Cancer, therefore, is the abnormal and uncontrolled growth of cells. When a carcinomatous process occur within the prostate gland, it usually begins form its outer zone. This means that a small prostate tumour may be present without causing symptoms in urination since it does not compress the urethra.
At the same time the tumour may easily infiltrate the outer capsule and extend outside of the prostate. Growth of cancer cells is uncontrolled, so a malignant tumour can invade adjacent organs (local extension), or grow in other parts of the body (metastasis).
Prostate cancer is the commonest cancer in men and the second cause of death due to neoplastic disease after lung cancer. An histological-only (subclinical) form is very common and its incidence does not vary across races and places, unlike clinical (symptom-causing) form which is less frequent but shows racial (commonest in people of African origin) and geographical (commonest in Nordic countries, lower in Mediterranean region, very low in Asia) variations.
Cancer seems to be directly related to age and hormonal status of patients. Genetic factors determined by race and inheritance, as well as dietary factors, are involved.