Types of testicular cancer

There are different types of testicular cancer. The type of cancer depends on which type of cell it started in. Knowing the type helps your doctor decide which treatment you need.

Most testicular cancers are a type called germ cell tumours. The 2 main types of testicular germ cell tumours are:

• seminomas
• non seminomas

There are also some rarer types of testicular cancer.

Germ cell tumours

Most testicular cancers start in cells known as germ cells and are called germ cell tumours. Germ cells in men produce sperm.  

Testicular germ cell tumours can develop from germ cell neoplasia in situ (GCNIS). GCNIS means that there are abnormal cells in the testicle. The cells look abnormal under the microscope. But they are only in the small tubes inside the testicle (the seminiferous tubules). It hasn’t spread into other parts of the testicle. It isn't cancer and doesn’t cause symptoms.

GCNIS can become an invasive cancer. Around 50 out of 100 (around 50%) of men with GCNIS will develop cancer within 5 years. The abnormal cells grow beyond the tubules into other parts of the testicles. The cancer cells can then spread into the lymph nodes and to other parts of the body. But GCNIS doesn’t always progress and become an invasive cancer.

There are two main groups of testicular germ cell tumours:

• Tumours that develop from GCNIS. These are the most common type that develop after puberty .
• Tumours that do not develop from GCNIS. These are less common and are usually diagnosed either in younger children, or in older men.

Testicular cancers that develop from abnormal cells (GCNIS)

These testicular tumours usually develop after puberty. They are sometimes described as post pubertal tumours. The main types of testicular germ cell tumours that develop from GCNIS are:

• seminomas
• non seminomas

Some germ cell tumours contain a mixture of seminoma and non seminoma cells. These are called mixed germ cell tumours.

Seminoma tumours

Around 55 to 60 out of every 100 testicular cancers (around 55 to 60%) are pure seminomas. 

Non seminoma tumours

Most other testicular germ cell tumours are non seminomas. Non seminomas develop from different types of cells. Some non seminomas develop from just one type of cell. And some develop from a mixture of cell types.

Types of non seminoma tumours include:

• teratoma (post pubertal type)
• embryonal carcinoma
• choriocarcinoma
• yolk sac tumours (post pubertal type)

So, for example, you might have a mix of some teratoma cells and some embryonal carcinoma cells. It's also possible to have pure teratomas. These non seminoma types are all treated in the same way.

Mixed germ cell tumours

Some testicular tumours have both seminoma cells and non seminoma cells. Doctors usually treat these in the same way as non seminomas.

Testicular cancers that don’t develop from abnormal cells (GCNIS)

Some testicular tumours don’t develop from GCNIS. These include:

• mixed teratoma and yolk sac tumour (prepubertal type)
• spermatocytic tumour
• spermatocytic tumour with sarcomatous differentiation
• teratoma (prepubertal type)
• dermoid cyst
• epidermoid cyst
• yolk sac tumour (prepubertal type)
• well-differentiated neuroendocrine tumour (monodermal teratoma)

Prepubertal type

These testicular tumours usually develop in younger children before they go through puberty. They tend to be less aggressive than tumours that develop after puberty. They are less likely to spread or come back after treatment

Spermatocytic tumours 

These used to be called spermatocytic seminomas. They are more often diagnosed in older men, but it can be diagnosed in younger men. They are less aggressive and behave differently to seminomas and non seminomas. They are less likely to spread beyond the testicle and they usually need less intensive treatment.

Rare types of testicular cancer

Sex cord stromal tumours

These testicular tumours start in the stroma or the sex cords. The stroma and the sex cords are tissues that support the testicle and from which different cells develop. There are different types of sex cord stromal tumours. They are extremely rare, with only a few men diagnosed in the UK each year.  

They include:

• leydig cell tumours

• sertoli cell tumours

• granulosa cell tumours

• fibroma-thecoma family of tumours

• mixed and other sex cord stromal tumours

These types can be cancerous or benign and surgery can usually cure them. But if they do spread, these tumours can be harder to treat than testicular germ cell tumours. This is because these tumours don’t respond well to chemotherapy.