During a Gleason test, a pathologist inserts a biopsy needle into the prostate gland via the wall of the rectum to extract samples of prostate tissue and examines this tissue under a microscope to detect cancer, states WebMD. The pathologist also can insert the needle through the skin between the scrotum and the rectum. Viewing ultrasound images of the procedure on a video screen, the pathologist removes at least 12 core samples from the prostate.
Doctors use biopsy to determine the presence and aggressiveness of cancer in the prostate, states WebMD. Pathologists determine the Gleason score by comparing the cancer tissue pattern with normal tissue.
The cancerous tissue that appears the most normal is given grade 1, according to Healthline. The tissue that looks very much like normal tissue and isn't likely to spread quickly has a score between 2 and 4, explains WebMD. A score of 8 to 10 means that the cells are likely to be aggressive, as they have very few features of normal cells.
Apart from the Gleason test, doctors can perform other tests such as a bone scan, a digital rectal exam, a CT scan or an MRI, states Healthline. Doctors also can do a PSA test to determine the levels of prostate-specific antigen to establish the risk of developing cancerous cells.