Seminoma: Understanding Your Pathology Report

Section Editor: Trevor Flood MD FRCPC
October 22, 2026

Seminoma is a type of cancer that starts in the testicle. It is the most common testicular cancer in adults. Seminoma belongs to a group of cancers called germ cell tumors, which develop from the cells that normally produce sperm. Most seminomas are found while the cancer is still limited to the testicle, and seminoma is one of the most curable cancers in adults.

This article explains what seminoma is, how the diagnosis is made after the testicle is removed, and what the measurements in your seminoma pathology report mean. It also explains the pathologic stage and how your report’s findings shape the next steps in your care.

Who gets seminoma?

Seminoma most often affects men between 25 and 45, peaking in the 30s. That is about ten years later than most other testicular germ cell tumors. Seminoma is rare in children and uncommon after age 60. About half of all testicular germ cell tumors are seminomas.

What causes seminoma?

Seminoma develops from an early change in the testicle called germ cell neoplasia in situ, or GCNIS. In GCNIS, abnormal germ cells grow inside the small tubes of the testicle where sperm are made. These tubes are called seminiferous tubules, and they make up most of the testicle. When abnormal cells break out of the tubules into the surrounding tissue, they can form an invasive germ cell tumor, such as seminoma.

GCNIS is thought to begin before birth, while the testicles are developing. Why it later turns into cancer in some men is not fully understood. Factors that increase the risk of seminoma include:

An undescended testicle. A testicle that did not descend into the scrotum in early childhood carries a higher risk, even after surgical correction.
A previous testicular cancer. Men who have had a germ cell tumor in one testicle have a small risk of a new tumor in the other.
Family history. The risk is higher when a father or brother has had testicular cancer.
Problems with testicular development. Small testicles and reduced fertility are linked with a higher risk.

What are the symptoms of seminoma?

The most common symptom of seminoma is a painless lump or swelling in one testicle. Some men notice heaviness in the scrotum or a dull ache in the lower abdomen. A few men have pain or tenderness in the testicle. When seminoma spreads to the lymph nodes in the back of the abdomen, it can cause back pain. Some seminomas are found during tests for another reason, such as an ultrasound for infertility.

How is the diagnosis made?

The diagnosis of seminoma usually begins with a scrotal ultrasound, which shows a solid mass inside the testicle. Blood tests for tumor markers are also done before surgery, because some testicular tumors release these substances into the blood. A needle biopsy of the testicle is rarely performed. Instead, the whole testicle is removed through a cut in the groin in an operation called a radical orchiectomy. The surgery removes the testicle together with part of the spermatic cord, which carries the blood vessels and the tube for sperm.

A pathologist then examines the testicle first with the naked eye, then under the microscope. Seminoma consists of sheets of large, round tumor cells with clear cytoplasm. Thin bands of tissue containing many lymphocytes, a type of immune cell, divide the cells into groups. Small clusters of immune cells called granulomas are often present.

The pathologist also checks every part of the tumor for other types of germ cell tumor. If any other type is found, the tumor is not a pure seminoma. It is then called a mixed germ cell tumor, which is treated differently. Seminoma also differs from spermatocytic tumor, once called spermatocytic seminoma. Spermatocytic tumor affects older men, does not arise from GCNIS, and rarely spreads.

Some seminomas contain scattered large cells called syncytiotrophoblasts, which produce the hormone hCG. These cells can raise blood hCG levels. Your report may describe this as seminoma with syncytiotrophoblastic cells. This finding does not change the diagnosis of seminoma or its outlook.

Once seminoma is confirmed, a CT scan of the abdomen, pelvis, and chest checks whether the cancer has spread to lymph nodes or other organs. Your pathologist may also have used special stains to confirm the diagnosis, which are described in the next section.

Immunohistochemistry

Immunohistochemistry uses antibodies to show which proteins tumor cells make. In seminoma, pathologists use immunohistochemistry to confirm the diagnosis and to separate seminoma from other germ cell tumors, which are treated differently. The stains used vary between laboratories, but typical results in seminoma include:

OCT3/4. Seminoma cells are positive for OCT3/4. This protein is found in seminoma and embryonal carcinoma, two closely related germ cell tumors.
SALL4. Seminoma cells are positive for SALL4. This protein is found in almost all germ cell tumors and helps confirm that the tumor started from germ cells.
CD117 and D2-40. Seminoma cells are usually positive for both proteins. These results are typical of seminoma and help separate it from embryonal carcinoma.
CD30. Seminoma cells are usually CD30-negative. A positive result in part of the tumor suggests an area of embryonal carcinoma.
Keratins. Seminoma cells are usually negative or only weakly positive for keratins. Strong staining suggests a different type of germ cell tumor.

Not every seminoma needs all these stains, and when the tumor looks typical under the microscope, pathologists may use only a few.

Blood tumor markers (AFP, hCG, and LDH)

Tumor markers are substances in the blood that some germ cell tumors release. For seminoma, the three markers tested are alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH). We measure them before orchiectomy and again after. These results are reported separately from the pathology report, but they work together with it.

AFP. Pure seminoma does not produce AFP, so elevated AFP suggests part of the tumor is likely a different germ cell type. This is true even if the pathologist did not see that other type under the microscope. In that case, the tumor is usually treated as a nonseminoma.
hCG. hCG is normal in most men with seminoma, and a mild rise can come from syncytiotrophoblast cells within the seminoma.
LDH. LDH is not specific to seminoma, and a raised level usually reflects a larger amount of cancer in the body.

We use marker levels measured after surgery to assign the S category in staging, described below. Our article on tumor markers in your blood test explains these tests in more detail.

Histologic grade

Unlike many other cancers, seminoma is not given a histologic grade. Grade describes how different cancer cells look from normal cells, and many other cancers are graded to predict behavior. Seminoma cells look very similar from one tumor to the next, so grading adds no useful information. Your seminoma pathology report will not include a grade, as expected.

Tumor size

The pathologist measures the seminoma in the removed testicle and reports its greatest dimension in centimeters. If there is more than one tumor nodule, the pathologist usually measures the largest and lists the others separately.

Tumor size matters for two reasons in seminoma. First, size divides stage pT1 seminoma into pT1a (smaller than 3 cm) and pT1b (3 cm or larger). Second, a seminoma larger than 4 cm has a higher chance of coming back after surgery when no further treatment is given. Your care team uses the size to discuss options after surgery.

Rete testis invasion

The rete testis is a network of small channels near the top of the testicle that collects sperm before it moves into the epididymis. Rete testis invasion means seminoma cells have grown into the tissue around these channels. Your report will say whether rete testis invasion is present or not identified.

Rete testis invasion does not change the pathologic stage of seminoma. However, it is linked with a higher chance that the cancer will come back after surgery alone. Together with tumor size larger than 4 cm, it helps your team estimate your risk of relapse. Sometimes abnormal GCNIS cells spread along the lining of the channels without invading the surrounding tissue. This is called pagetoid spread, and it is not counted as rete testis invasion.

Tumor extension

Tumor extension describes how far the seminoma has grown beyond the testicle, although most seminomas stay within it. The pathologist examines the nearby tissues to see whether tumor cells have reached any of these structures:

Hilar soft tissue. The fatty tissue at the back of the testicle, where blood vessels enter and leave.
Epididymis. The coiled tube on the back of the testicle that stores sperm.
Tunica vaginalis. The thin outer lining that covers the testicle. Growth through this lining is called perforation of the tunica vaginalis.
Spermatic cord. The cord that runs from the testicle up into the groin.
Scrotum. The skin and tissue that hold the testicles.

Growth into any of these structures increases the tumor stage (pT). Growth into the tunica albuginea, the tough capsule directly around the testicle, does not raise the stage on its own.

Lymphovascular invasion

Lymphovascular invasion means seminoma cells were seen inside a blood vessel or lymphatic channel. These vessels carry blood and fluid away from the testicle, so tumor cells inside them can spread to lymph nodes or other organs. Your report will describe lymphovascular invasion as present, not identified, or cannot be determined.

In seminoma, lymphovascular invasion changes the stage, so always report it. A tumor limited to the testicle is pT1 without lymphovascular invasion but pT2 with it.

Germ cell neoplasia in situ (GCNIS)

Germ cell neoplasia in situ, or GCNIS, is the early change that can develop into seminoma. In GCNIS, abnormal germ cells line the seminiferous tubules but have not broken out into the surrounding tissue. GCNIS is found in the testicle next to most seminomas.

Your report may mention GCNIS in the tissue around the tumor. This is an expected finding and does not change the stage, because the invasive seminoma already sets the stage. If GCNIS is the only change found in a testicle, stage it as pTis.

Scar or regressed germ cell tumor

Sometimes a seminoma shrinks or disappears inside the testicle before surgery, leaving only a scar, in a process called regression. Your report may describe a scar, fibrosis, or a regressed germ cell tumor. The pathologist makes this diagnosis when the scar contains GCNIS or coarse calcifications inside the tubules.

A regressed tumor matters most when cancer has been found elsewhere in the body, such as in lymph nodes at the back of the abdomen. In that situation, the scar shows that the cancer most likely started in the testicle.

Surgical margins

A margin is the cut edge of tissue removed during surgery. After a radical orchiectomy for seminoma, the most important margin is the end of the spermatic cord, which is the last tissue cut by the surgeon. Your report will describe the margins in one of these ways:

Negative margin. No seminoma cells are seen at any cut edge, which means the tumor was completely removed.
Positive margin. Seminoma cells are present at a cut edge, usually the spermatic cord margin. This means some tumor may remain in the body, and your care team will consider whether further treatment is needed.

When only part of the testicle has been removed, in an operation called a partial orchiectomy, the report also describes the margin in the remaining testicle.

Lymph nodes

Lymph nodes are small immune organs found throughout the body. Seminoma usually spreads first to the retroperitoneal lymph nodes at the back of the abdomen. These nodes are not removed during a radical orchiectomy, so most seminoma pathology reports from orchiectomy do not include any lymph nodes.

When lymph nodes are removed in a later operation called a retroperitoneal lymph node dissection, the pathologist reports:

Number of lymph nodes. How many nodes were examined, and how many contained seminoma.
Size. The size of the largest tumor deposit or the largest mass of involved nodes.
Extranodal extension. Whether cancer cells have broken through the outer capsule of a lymph node into surrounding tissue. Extranodal extension raises the nodal stage to at least pN2.

A lymph node described as negative contains no cancer cells, while a lymph node described as positive contains seminoma cells.

Pathologic stage (pTNM)

Seminoma pathologic stage is based on the tumor in the removed testicle (pT) and any lymph nodes examined (pN). It uses the TNM staging system in the 8th edition of the AJCC Cancer Staging Manual, which the current CAP testis protocol uses. Spread to distant organs (M) is usually determined by imaging, not by the pathologist.

Tumor stage (pT)

pTis. Only germ cell neoplasia in situ (GCNIS) is present, with no invasive tumor.
pT1a. The seminoma is limited to the testicle, has no lymphovascular invasion, and is smaller than 3 cm. Growth into the rete testis or the tunica albuginea is still pT1.
pT1b. The seminoma is limited to the testicle, has no lymphovascular invasion, and is 3 cm or larger.
pT2. The seminoma is limited to the testicle with lymphovascular invasion. A tumor that grows into the hilar soft tissue or the epididymis, or through the tunica vaginalis, is also pT2.
pT3. The seminoma grows directly into the spermatic cord soft tissue.
pT4. The seminoma grows into the scrotum.
pT0. No tumor is found in the testicle, a result that may be used when only a scar from a regressed tumor remains.

Sometimes seminoma cells are found in the spermatic cord, separate from the main tumor, carried there in a blood vessel. Under the AJCC 8th edition, this is treated as a deposit of spread cancer and staged as pM1, not pT3. Older reports written under the 7th edition staged this finding as pT3.

Nodal stage (pN)

pN0. No cancer is found in any of the lymph nodes examined.
pN1. Cancer is found in up to 5 lymph nodes, and no node or mass of nodes is larger than 2 cm.
pN2. The largest node or mass of nodes is larger than 2 cm but not larger than 5 cm. More than 5 positive nodes, or extranodal extension, is also pN2.
pN3. A lymph node mass is larger than 5 cm.
pNX. Lymph nodes were not sent for examination, which is the usual result after a radical orchiectomy.

The overall seminoma stage group does not match the pathologic stage in your report. Your care team assigns the stage group by combining the pathology findings, the CT scans, and the blood tumor markers (the S category, from S0 to S3). In broad terms, the stage groups are:

Stage I. The cancer is limited to the testicle and nearby structures, with no spread to lymph nodes or distant organs.
Stage II. The cancer has spread to the lymph nodes at the back of the abdomen. Stages IIA, IIB, and IIC reflect the size of the involved nodes.
Stage III. The cancer has spread to distant lymph nodes, organs such as the lungs, or tumor marker levels are very high.

What is the prognosis?

The prognosis for seminoma is excellent, even when it has spread. About 3 in 4 people with seminoma have stage I disease at diagnosis. For stage I seminoma, more than 99 in 100 people are cured.

After surgery alone, about 12 to 20 in 100 people with stage I seminoma have the cancer come back. Most relapses appear in the lymph nodes at the back of the abdomen. That means about 4 in 5 never need further treatment. When the cancer does come back, it is almost always caught by regular scans and cured with further treatment. The relapse rate is lower for small tumors without rete testis invasion. It is higher when the tumor is larger than 4 cm or invades the rete testis. When both features are present, some studies report relapse in about 20 to 30 in 100 people.

Seminoma that has spread beyond the testicle is also very often curable; for stage IIA and IIB seminoma treated with chemotherapy, about 99 in 100 people survive. For seminoma that has spread more widely, an international system called IGCCCG, updated in 2021, divides people into two groups:

Good prognosis. The cancer has not spread to organs other than the lungs. About 95 in 100 people are alive five years later, and about 89 in 100 have no further growth of the cancer.
Intermediate prognosis. The cancer has spread to organs other than the lungs, such as the liver, bones, or brain. About 88 in 100 people are alive five years later, and about 79 in 100 have no further growth of the cancer.

Pathologic features on your seminoma report that are linked with a higher chance of the cancer spreading or coming back include:

Larger tumor size. A seminoma larger than 4 cm is more likely to come back after surgery alone.
Rete testis invasion. Invasion of the tissue around the rete testis raises the chance of relapse.
Lymphovascular invasion. Tumor cells in blood vessels or lymphatic channels can spread.
Spread beyond the testicle. Growth into the spermatic cord or scrotum is less common and indicates a higher stage.
Positive margin. Tumor at the spermatic cord margin means some cancer may remain.

What happens after the diagnosis?

After seminoma is confirmed on the orchiectomy specimen, the next steps depend mainly on the stage group. Tumor size and rete testis invasion also matter for stage I seminoma. A team that includes a urologist, a medical oncologist, and a radiation oncologist usually plans care.

For stage I seminoma, the options your team may discuss include:

Active surveillance. Regular checkups, blood tests, and CT scans, with treatment only if the cancer comes back. Current European and Canadian guidelines list surveillance as the preferred option for most people, because most will never relapse.
Chemotherapy with carboplatin. A short course of a single chemotherapy drug can lower the chance of relapse. Consider it when the tumor is larger than 4 cm or invades the rete testis.
Radiation therapy. Radiation to the lymph nodes at the back of the abdomen was once common. Today it is used less often because of long-term side effects.

For seminoma that has spread to lymph nodes or other organs, treatment usually involves chemotherapy combinations that include cisplatin. Radiation therapy may be considered for smaller lymph node deposits. Some specialized centers also offer surgery to remove lymph nodes for low-volume stage II seminoma, often as part of a clinical trial. The IGCCCG prognosis group helps your team decide how much chemotherapy is needed.

Removing one testicle usually does not affect fertility or hormone levels because the other testicle continues to work. Chemotherapy and radiation can lower sperm production, so sperm banking is usually discussed before any further treatment. Some men choose a testicular prosthesis, which can be placed during the orchiectomy or later. Follow-up visits continue for several years and include checks of testosterone and of the remaining testicle.

Questions to ask your doctor

Is my tumor a pure seminoma, or does it contain any other type of germ cell tumor?
What was the size of my seminoma, and is it pT1a or pT1b?
Did my report show rete testis invasion?
Was lymphovascular invasion present?
Did the seminoma grow into the spermatic cord or other nearby tissues?
Was the spermatic cord margin negative?
What were my AFP, hCG, and LDH levels before and after surgery?
What is my overall stage, and how was it decided?
What is my chance of relapse, and is surveillance a good option for me?
How often will I need scans and blood tests, and for how long?
Should I bank sperm before any further treatment?
Does my family history mean my brothers or sons should check their testicles?