Prostate cancer can affect different cell types within your prostate. The type of cell affected gives a cancer its specific name. Adenocarcinoma, cancer of the glandular cells of the prostate, is by far the most common type of prostate cancer. The grade of cancer indicated on the Gleason scale rates the likelihood that the tumor will spread. The stage of cancer indicates how far the tumor has spread. For both grading and staging, lower numbers indicate a better prognosis.
Affected Cells
The second most common cancer in men over 50 years of age in the United States, adenocarcinoma of the prostate, affects the cells that line the inner surface of the gland. According to the Merck Manual, patients with localized adenocarcinoma of the prostate have a good prognosis and are more likely to die with it than because of it.
Prostate sarcoma affects the connective tissue and is very unusual, most often occurring in young boys. Other infrequent cells affected by prostate cancer include squamous cell carcinoma (thin flat cells that line the prostate), ductal transitional carcinoma (originating in the urethra where it passes through the prostate), and undifferentiated cancer. These types of cancer do not respond well to treatment and have a poor prognosis. Hormones levels can contribute to the outcome of adenocarcinoma of the prostate but not the other types.
Gleason Score
Doctors "grade" cancer to rate its aggressiveness and likelihood of spreading by looking at the different types and proportions of normal cells versus cancerous cells in a biopsy. The two most common patterns of cell types in the biopsy are rated on a scale from 1 to 5 according to their degree of differentiation, where "undifferentiated" cells cannot be classified according to cell type because the cancer has changed their appearance. Addition of those two scores produces a Gleason score on a scale between 2 to 10. Lower scores indicate a better prognosis with a tumor that is less likely to spread. According to the Merck manual, well-differentiated cells give a Gleason score of 6 or less. A Gleason score of 10 indicates a very aggressive cancer.
Staging
If warranted, doctors perform additional test to indicate the "stage" of the prostate cancer, which defines its extent. A rating of Stage I indicates very early stage cancer that is confined to a very small (microscopic) area; a doctor would not even be able to feel this cancer in a digital rectal exam. Stage II prostate cancer affects a larger area, and a doctor can feel it during a digital rectal exam, but it remains confined to the prostate itself. If cancer spreads beyond the prostate to other neighboring tissues, the cancer is considered Stage III. In Stage IV cancer, the cancer has spread further and affects the lymph nodes and organs.
