Cancer that starts in the testicles is called testicular cancer and in this edition of the Cancer Pro blog, we have taken information from several highly reputable and globally recognised sources to help you have a clearer understanding of the various forms this cancer can take.

Types of testicular cancer

The testicles are made up of many types of cells, each of which can develop into one or more cancer types. It’s essential to know the kind of cell cancer started in and what kind of cancer it is because they differ in treatment and prognosis.

Germ cell tumours

More than 90% of cancers of the testicle start in cells known as germ cells. These are the cells that make sperm. The main types of germ cell tumours (GCTs) in the testicles are seminomas and non-seminomas. These types occur about equally. Many testicular cancers contain both seminoma and non-seminoma cells.

Seminomas

Seminomas tend to grow and spread more slowly than non-seminomas. The two main subtypes of these tumours are classical (or typical) seminomas and spermatocytic seminomas.

• Classical seminoma: More than 95% of seminomas are classical. These usually occur in men between 25 and 45.
• Spermatocytic seminoma: This rare type of seminoma tends to occur in older men. (The average age is about 65.) Spermatocytic tumours tend to grow more slowly and are less likely to spread to other parts of the body than classical seminomas.

Non-seminomas

These types of germ cell tumours usually occur in men between their late teens and early 30s. The four main types of non-seminoma tumours are embryonal carcinoma, yolk sac carcinoma, choriocarcinoma, and teratoma. Most tumours are a mix of different types (sometimes with seminoma cells, too), but this doesn’t change the treatment of most non-seminoma cancers.

Embryonal carcinoma: These cells are found in about 40% of testicular tumours, but pure embryonal carcinomas occur only 3% to 4% of the time. When seen under a microscope, these tumours can look like tissues of very early embryos.

Yolk sac carcinoma: These tumours are so named because their cells look like the early human embryo’s yolk sac. Other names for this cancer include yolk sac tumour, endodermal sinus tumour, infantile embryonal carcinoma, or orchidoblastoma. This is the most common form of testicular cancer in children (especially in infants), but pure yolk sac carcinomas are rare in adults.

When they occur in children, these tumours usually are treated successfully. But they’re of more concern when they occur in adults, especially if they are pure. Yolk sac carcinomas respond very well to chemotherapy, even if they have spread.

Choriocarcinoma: This is a scarce and fast-growing type of testicular cancer in adults. Pure choriocarcinoma is likely to spread rapidly to other parts of the body, including the lungs, bones, and brain.

Teratoma: Teratomas are germ cell tumours with areas that, under a microscope, look like three layers of a developing embryo; pure teratomas of the testicles are rare and do not increase AFP (alpha-fetoprotein) or HCG (human chorionic gonadotropin) levels. There are three main types of teratomas:

• Mature teratomas are tumours formed by cells a lot like the cells of adult tissues. They rarely spread and can usually be cured with surgery, but some come back after treatment.
• Immature teratomas are less well-developed cancers with cells that look like those of an early embryo. This type is more likely than a mature teratoma to grow into (invade) nearby tissues, spread (metastasise) outside the testicle, and come back years after treatment.
• Teratomas with somatic type malignancy are very rare. These cancers have some areas that look like mature teratomas but have other places where the cells have become a type of cancer that usually develops outside the testicle (such as sarcoma, adenocarcinoma, or even leukemia).

Carcinoma in situ of the testicle

Because it’s hard to find CIS before it becomes invasive, cancer experts disagree about CIS’s best treatment. Generally, it doesn’t cause symptoms or form a lump that you or the doctor can feel, and so many doctors worldwide consider observation (watchful waiting) to be the best treatment option.

The only way to diagnose testicular CIS is to have a biopsy. (This is a procedure to take out a tiny bit of tissue so it can be checked under a microscope.) Sometimes CIS is found incidentally (by accident) when a testicular biopsy is undertaken for another reason, such as infertility.

Stromal tumours

Tumours can also start in the supportive and hormone-producing tissues, or stroma, of the testicles. These tumours are known as gonadal stromal tumours. They make up less than 5% of adult testicular tumours but up to 20% of childhood testicular tumours. The main types are Leydig cell tumours and Sertoli cell tumours.

Leydig cell tumours

Most Leydig cell tumours are not cancer (benign). They seldom spread beyond the testicle and can often be cured with surgery. Still, a small number of Leydig cell tumours do spread to other parts of the body. These tend to have a poor outlook because they usually don’t respond well to chemo or radiation therapy.

Sertoli cell tumours

These tumours start in normal Sertoli cells, which support and nourish the sperm-making germ cells. Like the Leydig cell tumours, these tumours are usually benign. But if they spread, they typically don’t respond well to chemo or radiation therapy.

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