This article was last reviewed and updated on August 30, 2019.
by Jason Wasserman, MD PhD FRCPC
Seminoma is a type of testicular cancer.
It is the most common type of testicular cancer in adults.
The cancer cells in a seminoma look similar to the cells found normally in the testicle.
Your pathology report for seminoma will include important information include the tumour size and whether the cancer cells have spread outside of the testicle.
The male reproductive tract
The male reproductive tract includes two paired and oval shaped organs called testes (singular: testis). After puberty, the testes are responsible for making special cells called spermatozoa.
The testes are located in the scrotum which sits just outside of the pelvis. The testes are connected to the rest of the male reproductive tract by a long channel called the spermatic cord. Spermatozoa produced in the testes travel along the spermatic cord before exiting the body through the urethra at the end of the penis.
The testes are made up of millions of very small channels called seminiferous tubules. The inside of these channels are lined by special cells called germ cells which are responsible for making the spermatozoa. The process of making spermatozoa from germ cells is called spermatogenesis.
What is a seminoma?
Seminoma is a type of testicular cancer. Seminoma develops from the germ cells in the seminiferous tubules. It is the most common type of testicular cancer in men under the age of 50 years old.
All seminomas start the seminiferous tubules. When the cancer cells are still inside the seminiferous tubules, the disease is called germ cell neoplasia in situ. Once the cancer cells break out of the tubules and enter the surrounding tissue, the disease is called seminoma. The process of cancer cells breaking out of the tubules and into the surrounding tissue is called invasion.
The diagnosis of seminoma is usually made after the entire testis has been removed in a resection specimen. Occasionally, small sample of tissue will be removed first in a procedure called a biopsy and the diagnosis will be made on that tissue.
This is the size of the tumour measured in centimeters (cm). Tumour size will only be described in your report after the entire tumour has been removed. The tumour is usually measured in three dimensions but only the largest dimension is described in your report. For example, if the tumour measures 4.0 cm by 2.0 cm by 1.5 cm, your report will describe the tumour as being 4.0 cm.
The testes sit outside of the body in a structure called the scrotum. Within the scrotum, each testis is surrounded by two thin layers of tissue. The layer closest to the seminiferous tubules is called the tunica albuginea. The layer in between the scrotum and the tunica albuginea is called the tunica vaginalis.
The millions of seminiferous tubules in the testis join together in a structure called the rete testis which then exits the testis through a structure called the epididymis. The rete testis and epididymis meet in an area of the testis called the hilar soft tissue. After leaving the testis, the epididymis connects with a long tube called the spermatic cord which leads out of the scrotum.
All seminomas start in the seminiferous tubules but they may grow into any of the structures described above. The process of a tumour growing into any of these structures is called tumour extension.
Why is this important? Tumour extension into the tunica albuginea, hilar soft tissue, spermatic cord, or scrotum is important because it is associated with with prognosis and is used to determine the pathologic tumour stage.
Blood moves around the body through long thin tubes called blood vessels. Another type of fluid called lymph which contains waste and immune cells moves around the body through lymphatic channels.
Cancer cells can use blood vessels and lymphatics to travel away from the tumour to other parts of the body. The movement of cancer cells from the tumour to another part of the body is called metastasis.
Before cancer cells can metastasize, they need to enter a blood vessel or lymphatic. This is called lymphovascular invasion.
Why is this important? Lymphovascular invasion increases the risk that cancer cells will be found in a lymph node or a distant part of the body such as the lungs. Lymphovascular invasion is also used to determine the tumour stage (see Pathologic stage below).
A margin is any tissue that has to be cut by the surgeon in order to remove the tumour from your body. For most testis specimens, the most important margin is the spermatic cord.
In a seminoma, a margin is considered positive when cancer cells are seen at the very edge of the cut tissue.
Why is this important? A positive margin is associated with a higher risk that the tumour will come back (recur) in the same site after treatment.
Lymph nodes are small immune organs located throughout the body. Cancer cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour (see Lymphovascular invasion above). The movement of cancer cells from the tumour to a lymph node is called a metastasis.
Lymph nodes on the same side as the tumour are called ipsilateral while those on the opposite side of the tumour are called contralateral.
Your pathologist will carefully examine each lymph node for cancer cells. Lymph nodes that contain cancer cells are often called positive while those that do not contain any cancer cells are called negative. Most reports include the total number of lymph nodes examined and the number, if any, that contain cancer cells.
A group of cancer cells inside of a lymph node is called a tumour deposit. If a tumour deposit is found, your pathologist will measure the deposit and the largest tumour deposit found will be described in your report.
Extranodal extension (ENE)
All lymph nodes are surrounded by a capsule. Extranodal extension (ENE) means that cancer cells have broken through the capsule and into the tissue that surrounds the lymph node.
Why is this important? Cancer cells inside a lymph node and extranodal extension are both associated with worse prognosis and are used to determine the nodal stage (see Pathologic stage below).
Pathologic stage (pTMN)
The pathologic stage for seminoma 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 more advanced disease and worse prognosis.
Tumour stage (pT) for seminoma
Seminoma is given a tumour stage between 1 and 4 based on size of the tumour, the extent of tumour extension, and the presence of lymphovascular invasion.
Tis - Cancer cells are only seen inside the seminiferous tubules. There is no invasive tumour seen. This is the same as germ cell neoplasia in situ.
T1 - The tumour is only seen in the testis. It does not extend into any of the surrounding tissue.
T2 - The tumour is only seen in the testis AND lymphovascular invasion is seen OR the tumour extends into the hilr soft tissue, epididymis, or tunica albuginea.
T3 - The tumour extends into the spermatic cord.
T4 - The tumour extends into the scrotum.
Nodal stage (pN) for seminoma
Seminoma is given a nodal stage of 0 to 3 based on the number of lymph nodes with cancer cells, the size of the largest lymph node with cancer cells, and the presence of extranodal extension.
Nx - No lymph nodes were sent for pathologic examination.
N0 - No cancer cells are seen in any lymph nodes examined.
N1 - Cancer cells are seen inside no more than 5 lymph nodes and none of the lymph nodes are larger than 2 cm.
N2 - Cancer cells are seen in more than 5 lymph nodes but none of the lymph nodes are over 5 cm OR extranodal extension is seen.
N3 - Cancer cells are seen in a lymph node over 5 cm.
Metastatic stage (pM)
Seminoma is given a metastatic stage of 0 or 1 based on the presence of cancer cells at a distant site in the body (for example a bone).
The metastatic stage can only be determined if tissue from a distant site is submitted for pathological examination. Because this tissue is rarely present, the metastatic stage cannot be determined and is listed as MX.
Pathologic changes in the testis outside of the tumour
Areas of the testis outside of the tumour will be carefully examined for spermatogenesis and atrophy.
Spermatogenesis describes the normal production of spermatozoa from germ cells. The presence of spermatogenesis means that the testicular tissue outside of the tumour was functioning normally.
Atrophy (or atrophic) is a word pathologists used to describe tissue that has decreased in size and function. Atrophy in the testis means that the seminiferous tubules are no longer producing normal spermatozoa. Atrophy is commonly seen in the tissue around a seminoma.
Scar or regressed germ cell tumour
Some seminomas decrease in size or even disappear entirely before the tumour is removed from the body. This process is called regression. If the process of regression is complete, your pathologist may only see a scar where the tumour used to be when your tissue is examined through the microscope.
In another situation, your pathologist may only see an early form of cancer called germ cell neoplasia in situ. The finding of germ cell neoplasia in situ within a scar suggests that a seminoma was there previously but has now regressed.