Adenocarcinoma of the prostate gland

by Trevor A. Flood, MD FRCPC
January 5, 2024

Adenocarcinoma (prostatic adenocarcinoma) is the most common type of prostate cancer. This type of cancer may also be described as acinar adenocarcinoma because it is made up of groups of tumour cells forming small glands called acini. It develops from epithelial cells normally found in the prostate gland. Adenocarcinoma of the prostate is a relatively common cancer among older men and the risk of developing this type of cancer increases after a man turns 50 years old.

This article will help you understand your diagnosis and your pathology report for adenocarcinoma of the prostate gland.

Is adenocarcinoma of the prostate gland an aggressive disease?

Adenocarcinoma of the prostate gland can appear and progress very differently in each person. Many tumours grow slowly. Some men can live many years before the cancer is detected. Some tumours are aggressive. Aggressive cancer should be treated right away.

What are the risk factors for developing adenocarcinoma of the prostate?

The risk factors for developing adenocarcinoma of the prostate include older age, a family history of prostate cancer, African or Caribbean ethnicity, and obesity.

How is the diagnosis of adenocarcinoma of the prostate made?

Most tumours in the prostate are found after a doctor manually examines your prostate gland. This procedure is called a digital rectal examination. If an unusual lump is found, the next step is to take several small tissue samples from the prostate in a procedure called a core needle biopsy. Most biopsies usually involve 10 to 15 samples of tissue taken from different parts of the prostate. A biopsy can also be done after a blood test shows high levels of the prostate-specific antigen (PSA).

Your pathologist will then examine the tissue samples under a microscope.  What they see (the microscopic features) will help them predict how the disease will behave. These same features will help you and your doctors decide which treatment options are best for you.  These options may include active surveillance (see below), radiation, or surgery to remove the tumour.

Your pathology report for adenocarcinoma of the prostate gland

The information found in your pathology report for adenocarcinoma of the prostate gland will depend on the type of procedure performed. In addition to the diagnosis, most biopsy reports will include the number of cores (samples) that show cancer and the percentage of each core made up of cancer cells. This is called tumour quantification. Each sample will be given a Gleason grade and Gleason score. If perineural invasion or extraprostatic extension is seen, it will also be described in your report. If surgery is performed to remove the entire tumour, additional information such as the assessment of margins, seminal vesicle invasion, bladder neck invasion, and any lymph nodes examined will also be included in your report. These features are described in the sections below.

Gleason grade, Gleason score, and Gleason group

Your pathology report for prostatic adenocarcinoma will likely contain a lot of information about the Gleason grade and the Gleason score.  Both are made up of numeric scales. The Gleason grade ranges from 1-5 and the Gleason score ranges from 2 and 10. Both the Gleason grade and Gleason score are important because they help predict how the tumour will behave over time.

Gleason grade

Your pathologist will decide the Gleason grade after examining the tissue under the microscope. The grade is based on how different the tumour cells look compared to normal glands in the prostate. Your pathologist will then give the tumour a number between 1 and 5. Tumours that look similar to normal glands are given a lower number.  These tumours tend to be slow-growing and less aggressive.  Tumours that do not look like normal glands are given a higher number and tend to be more aggressive.  These tumours can grow quickly and spread.

Gleason grade 1 and 2 tumours are not typically diagnosed. These grades are noted as part of your health history only. As a result, Gleason grades range from 3-5 (instead of 1-5) and Gleason scores range from 6-10 (instead of 2-10).

Gleason score

The Gleason score is calculated by adding up the two most common Gleason grade numbers in your tumour. For example, if your tumour is made up of 70% Gleason grade 3 and 30% Gleason grade 4, then your Gleason score would be 3+4=7.  If only one Gleason grade is seen then the primary and secondary patterns are given the same grade.  For example, if your tumour is made up 100% of Gleason grade 3, then your Gleason score is 3+3=6. The Gleason score is important because it can be used to predict the behaviour of the tumour.

Gleason group

The prostate cancer Gleason Grade group is a new grading system that is based on information from the Gleason score. The Grade groups range from 1-5. See the table below for more information. All tumours within a Gleason Grade group are likely to behave similarly and patients within the same group have a similar prognosis.

What does active surveillance mean?

Active surveillance is a treatment option for men who have low-grade (Gleason score 3+3=6 or Grade group 1) prostate cancer detected by a biopsy. Since the cancer is growing slowly, there is no need to remove it right away because it likely poses no risk to the patient. Active surveillance avoids invasive treatments for low-risk cancer that is growing slowly.

Active surveillance involves monitoring the patient with:

• Regular prostate-specific antigen (PSA) blood tests.
• Regular manual examinations of the prostate (digital rectal examination).
• Occasional core needle biopsies.

Patients will be offered treatment (surgery or radiation) at the first sign that the prostate cancer has progressed or if it has changed into a more aggressive type of tumour (pathologists call this ‘transformation’).

Tumour quantification

Tumour quantification is the percentage of the prostate replaced by cancer cells. This gives an estimate of how big the tumour is. Your pathology report will describe how many tissue samples show cancer cells. Your report will also describe what percentage of each sample was replaced by cancer cells. This information will help your doctor and you decide which treatment options are best for you.

Extraprostatic extension​​

Extraprostatic extension describes cancer cells that have moved outside of the prostate and into the tissue surrounding the prostate. If cancer cells are seen in the tissue outside of the prostate, it will be described in your report. ​Extraprostatic extension is associated with a worse prognosis and is used to determine the tumour stage (see Pathologic stage below).

Seminal vesicle invasion​

The seminal vesicles are organs that are located behind the bladder and above the prostate. Each person has two seminal vesicles and one is located on each side of the prostate. These organs produce and store the fluid that is sent to the prostate to feed and move sperm. Seminal vesicle invasion means that cancer cells have spread directly from the prostate into the seminal vesicles. Seminal vesicle invasion is associated with a worse prognosis and is used to determine the tumour stage (see Pathologic stage below).

Bladder neck invasion

​The bladder rests above the prostate gland. Bladder neck invasion means that cancer cells have spread directly from the prostate into the lower part of the bladder known as the bladder neck. Invasion of the bladder neck is associated with a worse prognosis and is used to determine the tumour stage (see Pathologic stage below).

Perineural invasion

Pathologists use the term “perineural invasion” to describe a situation where cancer cells attach to or invade a nerve. “Intraneural invasion” is a related term that specifically refers to cancer cells found inside a nerve. Nerves, resembling long wires, consist of groups of cells known as neurons. These nerves, present throughout the body, transmit information such as temperature, pressure, and pain between the body and the brain. The presence of perineural invasion is important because it allows cancer cells to travel along the nerve into nearby organs and tissues, raising the risk of the tumour recurring after surgery.

Lymphovascular invasion

Lymphovascular invasion occurs when cancer cells invade a blood vessel or lymphatic channel. Blood vessels, thin tubes that carry blood throughout the body, contrast with lymphatic channels, which carry a fluid called lymph instead of blood. These lymphatic channels connect to small immune organs known as lymph nodes, scattered throughout the body. Lymphovascular invasion is important because it enables cancer cells to spread to other body parts, including lymph nodes or the lungs, via the blood or lymphatic vessels.

Margins

In pathology, a margin refers to the edge of tissue removed during tumour surgery. The margin status in a pathology report is important as it indicates whether the entire tumour was removed or if some was left behind. This information helps determine the need for further treatment.

Pathologists typically assess margins following a surgical procedure like an excision or resection, aimed at removing the entire tumour. Margins aren’t usually evaluated after a biopsy, which removes only part of the tumour. The number of margins reported and their size—how much normal tissue is between the tumour and the cut edge—vary based on the tissue type and tumour location.

Pathologists examine margins to check if tumour cells are present at the tissue’s cut edge. A positive margin, where tumour cells are found, suggests that some cancer may remain in the body. In contrast, a negative margin, with no tumour cells at the edge, suggests the tumour was fully removed. Some reports also measure the distance between the nearest tumour cells and the margin, even if all margins are negative.

Lymph nodes

Lymph nodes are small immune organs found throughout the body. Cancer cells can spread from a tumour to lymph nodes through small lymphatic vessels. For this reason, lymph nodes are commonly removed and examined under a microscope to look for cancer cells. The movement of cancer cells from the tumour to another part of the body such as a lymph node is called a metastasis.

Cancer cells typically spread first to lymph nodes close to the tumour although lymph nodes far away from the tumour can also be involved. For this reason, the first lymph nodes removed are usually close to the tumour. Lymph nodes further away from the tumour are only typically removed if they are enlarged and there is a high clinical suspicion that there may be cancer cells in the lymph node.

A neck dissection is a surgical procedure performed to remove lymph nodes from the neck. The lymph nodes removed usually come from different areas of the neck and each area is called a level. The levels in the neck include 1, 2, 3, 4, and 5. Your pathology report will often describe how many lymph nodes were seen in each level sent for examination. Lymph nodes on the same side as the tumour are called ipsilateral while those on the opposite side of the tumour are called contralateral.

If any lymph nodes were removed from your body, they will be examined under the microscope by a pathologist and the results of this examination will be described in your report. “Positive” means that cancer cells were found in the lymph node. “Negative” means that no cancer cells were found. If cancer cells are found in a lymph node, the size of the largest group of cancer cells (often described as “focus” or “deposit”) may also be included in your report. Extranodal extension means that the tumour cells have broken through the capsule on the outside of the lymph node and have spread into the surrounding tissue.

The examination of lymph nodes is important for two reasons. First, this information is used to determine the pathologic nodal stage (pN). Second, finding cancer cells in a lymph node increases the risk that cancer cells will be found in other parts of the body in the future. As a result, your doctor will use this information when deciding if additional treatment such as chemotherapy, radiation therapy, or immunotherapy is required.

Pathologic stage (pTNM)

​​The pathologic stage for adenocarcinoma of the prostate gland is based on the TNM staging system, an internationally recognized system created by the American Joint Committee on Cancer. This system uses information about the primary tumour (T), lymph nodes (N), and distant metastatic disease (M)  to determine the complete pathologic stage (pTNM). Your pathologist will examine the tissue submitted and give each part a number. In general, a higher number means a more advanced disease and a worse prognosis.

Tumour stage (pT)

Your pathologist will give your tumour a tumour stage between T2 and T4 based on what they have observed after examining your prostate specimen under the microscope.  The tumour stage is based on how far the cancer cells have spread outside of the prostate.

• T2 – The tumour is found inside the prostate only.
• T3 – The cancer cells have spread outside of the prostate and into the fat, seminal vesicles, and/or into the bladder neck.
• T4 – The cancer cells have spread into other nearby organs or tissues such as the rectum or pelvic wall.​

Nodal stage (pN)

Adenocarcinoma of the prostate gland is given a nodal stage of N0 or N1 based on the presence of cancer cells in a lymph node. If no lymph nodes contain cancer cells, the nodal stage is N0. If no lymph nodes are sent for pathological examination, the nodal stage cannot be determined and the nodal stage is listed as NX.

Other helpful resources

Atlas of Pathology