Malignant tumors are cancer and often do invade surrounding tissue and spread, or metastasize, to other parts of the body. The exact cause of prostate cancer is unknown, but hormones play a role and genetic factors also are suspected. More than half of these cancers develop from the rear portion of the prostate, closest to the rectum. For this reason, rectal examinations are an effective way to detect a tumor. Less common types like leiomyosarcoma and rhabdomyosarcoma begin in the connective tissues surrounding the prostate.
Tumors also can spread from the bladder, the adrenal gland or other nearby organs.
Types of tumors that aren't cancer but may soon become cancer are called prostatic intraepithelial neoplasia. Men with these cell growths need to be observed closely and have biopsies periodically. Prostate cancer is categorized in four stages. In its first stage, Stage A, the cancer is generally confined to the prostate. The cancer is rarely found in this stage because it is too small to be detected.