Germ Cell Neoplasia In Situ (GCNIS): Understanding Your Pathology Report

Section Editor: Trevor Flood MD FRCPC
October 23, 2026

Germ cell neoplasia in situ, or GCNIS, is a precancerous change in the testicle. In GCNIS, abnormal germ cells grow inside the small tubes of the testicle where sperm are made, but they have not broken out into the surrounding tissue. GCNIS is not cancer yet. However, it is the starting point for most testicular cancers in adults, and it can turn into an invasive germ cell tumor over time.

GCNIS is most often found in the testicle next to a testicular cancer that has been removed. Less often, it is found on its own in a small biopsy of the testicle. This article explains what GCNIS is, how it is found, and what it means when GCNIS appears in your pathology report, either beside a tumor or on its own.

Older reports may call this change intratubular germ cell neoplasia, unclassified (IGCNU), or carcinoma in situ of the testis. These names describe the same thing.

Who gets germ cell neoplasia in situ?

Germ cell neoplasia in situ is found mainly in young and middle-aged men, the same group most likely to develop testicular cancer. It is present in the testicle in most adult men with testicular germ cell tumors. GCNIS is less common in men without a testicular tumor. It is more likely in men with risk factors for testicular cancer, such as those listed in the next section.

What causes germ cell neoplasia in situ?

Germ cell neoplasia in situ is thought to begin before birth, while the testicles are developing. Some early germ cells fail to mature normally and remain immature in the tubules. After puberty, these cells can start to grow and form GCNIS. Factors linked with a higher chance of GCNIS include:

A previous testicular cancer. GCNIS is found in the other testicle in up to 9 in 100 men who have had testicular cancer and then have a biopsy.
An undescended testicle. A testicle that did not descend into the scrotum in early childhood carries a higher risk, even after surgical correction.
A small testicle. A testicle with a volume of less than 12 mL is more likely to contain GCNIS.
Problems with testicular development. Reduced fertility, a low sperm count, and some differences of sex development are linked with a higher risk.
Family history. The risk is higher when a father or brother has had testicular cancer.

What are the symptoms of germ cell neoplasia in situ?

Germ cell neoplasia in situ does not cause any symptoms. It does not form a lump, and it usually cannot be seen on an ultrasound. A pathologist finds GCNIS only when examining testicular tissue under a microscope.

How is the diagnosis made?

A pathologist diagnoses germ cell neoplasia in situ by examining testicular tissue under a microscope. Most often, the tissue comes from a radical orchiectomy, an operation to remove a testicle that contains a tumor. In that case, the pathologist finds GCNIS in the normal-looking testicle around the tumor.

Less often, pathologists find GCNIS in a small surgical biopsy of the testicle. A biopsy may be taken from the other testicle in men with testicular cancer who have a higher risk. Examples include a small testicle or a history of an undescended testicle. Current European guidelines recommend sampling two sites in the testicle. GCNIS may also be found by chance in a biopsy done to investigate infertility.

Under the microscope, the GCNIS cells are large, with clear cytoplasm and large nuclei. They sit in a single row along the inside edge of the seminiferous tubules, and the tubules around them usually make little or no sperm. Because the abnormal cells can be scattered, pathologists usually use special stains to confirm the diagnosis.

Immunohistochemistry

Immunohistochemistry uses antibodies to show which proteins cells make. In germ cell neoplasia in situ, pathologists use immunohistochemistry to highlight abnormal germ cells and distinguish them from normal sperm-producing cells. The stains used vary between laboratories, but typical results in GCNIS include:

OCT3/4. GCNIS cells are OCT3/4-positive, while normal adult germ cells are negative. This makes OCT3/4 the most useful stain for finding GCNIS.
CD117 and D2-40. GCNIS cells are usually positive for these proteins as well.
SALL4. GCNIS cells are SALL4-positive, but some normal germ cells are also positive, so this stain is less specific.
PLAP. GCNIS cells are often positive for placental alkaline phosphatase (PLAP), an older stain that some laboratories still use.

Not every case needs all these stains, and when GCNIS cells are easy to see, labs may use only one or two.

GCNIS found next to a testicular tumor

When germ cell neoplasia in situ is found next to a testicular cancer, it confirms that the tumor developed from GCNIS. This is expected for seminoma, embryonal carcinoma, mixed germ cell tumor, and the postpubertal type of yolk sac tumor. In this situation, GCNIS does not change the stage or treatment because the invasive tumor determines both.

GCNIS is not found with every testicular tumor. It is absent in spermatocytic tumor and in germ cell tumors of young children, which develop differently. Therefore, the presence or absence of GCNIS can help the pathologist determine which tumor type is present.

Sometimes GCNIS cells spread along the rete testis lining, a network of small channels near the top of the testicle. This is called pagetoid spread. It is not the same as tumor invasion of the rete testis, and the pathologist does not count it as rete testis invasion.

GCNIS and the pathologic stage

The pathologic stage of a testicular tumor uses the TNM system in the 8th edition of the AJCC Cancer Staging Manual. When germ cell neoplasia in situ is the only abnormal finding in a testicle, with no invasive tumor, it is given the stage pTis. The “is” stands for in situ, meaning the abnormal cells remain within the tubules where they started. When GCNIS is found next to an invasive tumor, the stage is set by the invasive tumor instead.

What is the risk that GCNIS will turn into cancer?

Germ cell neoplasia in situ on its own carries a high risk of becoming invasive cancer. When GCNIS is found in a testicle without a tumor, about half of men develop an invasive germ cell tumor within five years if it is not treated. The risk continues after that, so GCNIS is unlikely to resolve on its own.

The cancers that develop from GCNIS are usually found early with regular follow-up, and testicular germ cell tumors are among the most curable cancers in adults. Your care team weighs this high but treatable risk against the effects of treatment on fertility and hormone levels.

What happens after the diagnosis?

When doctors find germ cell neoplasia in situ next to a removed tumor, no separate treatment is needed for the GCNIS. That testicle has already been removed, and the next steps are planned around the invasive tumor.

When GCNIS is found on its own, the next steps depend on whether the other testicle is normal and on plans for having children. Options your team may discuss include:

Surveillance. Regular physical examinations and ultrasounds, with treatment if a tumor develops. This may be considered for men who want to father children, since it preserves fertility for a time.
Orchiectomy. Removal of the testicle with GCNIS. Consider this when the other testicle is normal.
Low-dose radiation therapy. Radiation to the testicle destroys the GCNIS cells. It is usually considered when GCNIS is found in a man’s only remaining testicle. Radiation causes permanent infertility and can lower testosterone production over time.

Chemotherapy given for testicular cancer does not reliably destroy GCNIS in the other testicle, so follow-up of that testicle continues after chemotherapy. Because treatment of GCNIS can affect fertility, sperm banking is usually discussed first. Men treated with radiation have their testosterone levels checked during follow-up, and some may need testosterone replacement.

Questions to ask your doctor

Was GCNIS found next to my tumor, or on its own?
Does GCNIS change my stage or treatment?
Which stains were used to confirm GCNIS?
Should my other testicle be biopsied?
What is my risk of developing an invasive tumor?
Is surveillance an option for me, and how often would I need checkups?
How would radiation or surgery affect my fertility and testosterone levels?
Should I bank sperm before any treatment?
How should I examine my testicles, and what changes should I report?
Does my family history mean my brothers or sons should be checked?