Testicular cancer is a malignant tumour that starts in cells of a testicle. Malignant means that it can spread, or metastasize, to other parts of the body.
The testicles are part of a man’s reproductive system. They are 2 egg-shaped organs. The testicles are covered by a sac of skin called the scrotum. The scrotum hangs below the penis, between the legs. Each testicle is held in the scrotum by a spermatic cord. The spermatic cord contains the vas deferens, blood vessels, lymph vessels and nerves. The testicles make sperm. They also make a male sex hormone called testosterone.
Cells in a testicle sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous, or benign, tumours such as benign teratomas and benign sex cord stromal tumours. They can also lead to non-cancerous conditions such as epididymitis, hydrocele and orchitis.
Changes to cells in a testicle can also cause precancerous conditions. This means that the cells are not yet cancer but there is a higher chance these abnormal changes will become cancer. The most common precancerous condition of the testicle is intratubular germ cell neoplasia, unclassified (IGCNU).
In some cases, changes to testicle cells can cause cancer. More than 90% of all testicular cancers are germ cell tumours. Germ cells are cells in the testicles that make sperm. The 2 main types of germ cell tumours that develop in the testicles are seminomas and non-seminomas.
Rare types of testicular cancer can also develop. These include sex cord stromal tumours and non-Hodgkin lymphoma of the testis.