Cancerous tumours of the testicle

A cancerous tumour of the testicle can grow into nearby tissue and destroy it. It can also spread (metastasize) to other parts of the body. Cancerous tumours are also called malignant tumours.

More than 90% of all testicular cancers are germ cell tumours. This type of cancer starts in germ cells, which are the cells that make sperm. The 2 main types of germ cell tumours that develop in the testicles are seminomas and non-seminomas. Each type of tumour grows differently and is treated differently.

Germ cell tumours can be made up of a mixture of seminoma and non-seminoma. These tumours are called mixed germ cell tumours. They are treated like non-seminomas.

Sometimes germ cell tumours start outside of the testicle. These tumours are called extragonadal germ cell tumours. Extragonadal germ cell tumours can start anywhere in the body, but they usually start in the area between the lungs (mediastinum), abdomen (retroperitoneum), lower spine or pineal gland in the brain.

Usually men with testicular cancer have a primary tumour in 1 of the 2 testicles. But about 2% to 4% of men with testicular cancer will develop testicular cancer in their other testicle too. The cancers can happen at the same time or develop at different times.

Seminomas grow slower than non-seminomas. Seminomas most often develop in men in their 40s.

Non-seminomas make up about 55% of all germ cell tumours. Non-seminomas happen most often in men between their late teens and 30s.

The cells in non-seminomas look very different from seminomas when seen under a microscope. There are 4 main types of non-seminomas. They are named and described based on what the cancer cells look like under a microscope.

Embryonal carcinoma is a type of non-seminoma that tends to grow quickly and spread outside of the testicle. These tumours look like very early embryos when seen under a microscope.

Yolk sac carcinoma is rare in adults, but it is the most common form of testicular cancer in children and babies. When yolk sac carcinomas develop in children, they usually respond very well to treatment.

Choriocarcinoma is a rare and aggressive type of testicular cancer. It can spread quickly to distant organs, including the lungs, bones and brain. Choriocarcinomas are usually part of a mixed germ cell tumour.

Teratoma has areas that look like each of the 3 layers of a developing embryo (endoderm, mesoderm and ectoderm). Pure teratomas are rare. This type of cancer is more often part of a mixed germ cell tumour.

Other types of testicular tumours can also develop but they are rare. They are called non–germ cell tumours.

Sex cord stromal tumours are also called sex cord gonadal stromal tumours. They start in cells of the stroma, which is supportive tissue in the testicle that makes hormones. There are 2 main types of stromal tumours:

• Leydig cell tumours
• Sertoli cell tumours

Most of these tumours are non-cancerous (benign), but some can be cancerous. Surgery is the main treatment for both non-cancerous and cancerous sex cord stromal tumours. Other treatments may be offered to treat a cancerous sex cord stromal tumour because it can spread to other parts of the body. Talk to your doctor about your treatment options for this type of testicular cancer.

The following are other rare cancerous tumours of the testicle.

Non-Hodgkin lymphoma of the testis starts in the epithelium of the testicle. Find out more about non-Hodgkin lymphoma.

Adenocarcinoma of the rete testis starts in a passageway that helps carry new sperm to the epididymis where they can mature.

Malignant mesothelioma of the tunica vaginalis starts in the layer that covers the testicles (tunica vaginalis). Find out more about mesothelioma.

Paratesticular rhabdomyosarcoma is a type of soft tissue sarcoma that starts outside of the testicle in the spermatic cord. Find out more about rhabdomyosarcoma.