by Trevor A. Flood, MD FRCPC
April 12, 2023
Prostatic adenocarcinoma is the most common type of prostate cancer. It develops from the glands normally found in the prostate gland. The risk of developing prostatic adenocarcinoma increases after a man turns 50 years old.
Prostatic adenocarcinoma 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.
The risk factors for developing prostatic adenocarcinoma include older age, a family history of prostate cancer, African or Caribbean ethnicity, and obesity.
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 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.
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 actually range from 3-5 (instead of 1-5) and Gleason scores range from 6-10 (instead of 2-10).
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.
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 in a similar manner and patients within the same group have a similar prognosis.
Active surveillance is a treatment option for men who have low-grade (Gleason score 3+3=6 or Grade group 1) prostatic adenocarcinoma 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:
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 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 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 (pT).
The seminal vesicles are organs that are located behind the bladder and above the prostate. Men have 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 (pT).
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 (pT).
Perineural invasion is a term pathologists use to describe cancer cells attached to a nerve. A similar term, intraneural invasion, is used to describe cancer cells inside a nerve. Nerves are like long wires made up of groups of cells called neurons. Nerves are found all over the body and they are responsible for sending information (such as temperature, pressure, and pain) between your body and your brain. Perineural invasion is important because the cancer cells can use the nerve to spread into surrounding organs and tissues. This increases the risk that the tumour will regrow after surgery.
Lymphovascular invasion means that cancer cells were seen inside a blood vessel or lymphatic vessel. Blood vessels are long thin tubes that carry blood around the body. Lymphatic vessels are similar to small blood vessels except that they carry a fluid called lymph instead of blood. The lymphatic vessels connect with small immune organs called lymph nodes that are found throughout the body. Lymphovascular invasion is important because cancer cells can use blood vessels or lymphatic vessels to spread to other parts of the body such as lymph nodes or the lungs.
In pathology, a margin is the edge of a tissue that is cut when removing a tumour from the body. The margins described in a pathology report are very important because they tell you if the entire tumour was removed or if some of the tumour was left behind. The margin status will determine what (if any) additional treatment you may require.
Most pathology reports only describe margins after a surgical procedure called an excision or resection has been performed for the purpose of removing the entire tumour. For this reason, margins are not usually described after a procedure called a biopsy is performed for the purpose of removing only part of the tumour. The number of margins described in a pathology report depends on the types of tissues removed and the location of the tumour. The size of the margin (the amount of normal tissue between the tumour and the cut edge) depends on the type of tumour being removed and the location of the tumour.
Pathologists carefully examine the margins to look for tumour cells at the cut edge of the tissue. If tumour cells are seen at the cut edge of the tissue, the margin will be described as positive. If no tumour cells are seen at the cut edge of the tissue, a margin will be described as negative. Even if all of the margins are negative, some pathology reports will also provide a measurement of the closest tumour cells to the cut edge of the tissue.
A positive (or very close) margin is important because it means that tumour cells may have been left behind in your body when the tumour was surgically removed. For this reason, patients who have a positive margin may be offered another surgery to remove the rest of the tumour or radiation therapy to the area of the body with the positive margin.
A negative margin means no cancer cells were seen at the cut edge of the tissue. In contrast, a positive margin means that cancer cells are seen at the cut edge of the tissue. Your pathologist will report any positive margins and the location of that margin. A positive margin is associated with an increased risk of the tumour coming back in the same area of the body.
Lymph nodes are small immune organs found throughout the body. Cancer cells can spread from a tumour to lymph nodes through small vessels called lymphatics. 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 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.
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. Most reports will include the total number of lymph nodes examined, where in the body the lymph nodes were found, and the number (if any) that contain cancer cells. If cancer cells were seen in a lymph node, the size of the largest group of cancer cells (often described as “focus” or “deposit”) will also be included.
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.
Pathologists often use the term “positive” to describe a lymph node that contains cancer cells. For example, a lymph node that contains cancer cells may be called “positive for malignancy” or “positive for metastatic carcinoma”.
Pathologists often use the term “negative” to describe a lymph node that does not contain any cancer cells. For example, a lymph node that does not contain cancer cells may be called “negative for malignancy” or “negative for metastatic carcinoma”.
All lymph nodes are surrounded by a thin layer of tissue called a capsule. Extranodal extension means that cancer cells within the lymph node have broken through the capsule and have spread into the tissue outside of the lymph node. Extranodal extension is important because it increases the risk that the tumour will regrow in the same location after surgery. For some types of cancer, extranodal extension is also a reason to consider additional treatment such as chemotherapy or radiation therapy.
The pathologic stage for prostatic adenocarcinoma is based on the TNM staging system, an internationally recognized system originally 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.
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.
Prostatic adenocarcinoma 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.
Prostatic adenocarcinoma is given a metastatic stage of M0 or M1 based on the presence of cancer cells at other locations in the body (for example a bone). The metastatic stage (pM) can only be determined if a pathologist examines the tissue from another site of the body. Because this tissue is not typically sent to the lab, the metastatic stage (pM) can not be determined and is listed as pMX.