Testicular cancer refers to cancer that develops within one or both of the testicles. Testicular cancer most commonly forms in germ cells, which are cells that produce sperm.

The two main types of testicular cancer include:

• Seminoma testicular cancer – the tumour does not include any subtypes. This typically grows more slowly compared to non-seminoma testicular cancer
• Non-seminoma testicular cancer – a rarer cancer where the tumour contains at least one of the following subtypes: teratoma, choriocarcinoma, yolk sac tumour and embryonal carcinoma, and develops more quickly than seminoma cancers

Testicular cancer is the most commonly diagnosed cancer in young New Zealand men, with 137 New Zealand men diagnosed with testicular cancer in 2013. However, it is most prevalent in men aged between 30 and 34 years.

Testicular cancer can be described in stages depending on how early or advanced the cancer is.

The TNM system is used to stage testicular cancer and helps doctors understand what your cancer looks like. TNM stands for:

• Tumour – the degree to which the tumour has affected other tissue.
• Node – is a measure of whether lymph nodes have been affected.
• Metastasis – the degree to which the cancer has spread to other organs of the body.

The TNM information, along with other tests helps determine the stage of your testicular cancer.

• Stage IA – the cancer is confined to the testicle and has not grown into the epididymis, hilar soft tissue, or lymphatic/blood vessels. The tumour may have grown into the inner membrane surrounding the testicle (tunica albuginea), but not the outer membrane (tunica vaginalis). If the tumour is seminoma cancer, it is smaller than 3 cm. Tumour markers are normal.
• Stage IB – the cancer has grown into the epididymis, hilar soft tissue, outer membrane (tunica vaginalis), lymphatic/blood vessels, spermatic cord or scrotum. Tumour markers are normal.
• Stage IS – the cancer might or might not have grown outside of the testicle, but has not spread to lymph nodes or distant areas of the body. At least one tumour marker is higher than normal.
• Stage IIA – the cancer has spread to no more than five nearby lymph nodes and none are larger than 2 cm. Tumour markers are normal or slightly high.
• Stage IIB – the cancer has spread to nearby lymph nodes and is between 2 cm and 5 cm in size. Tumour markers are normal or slightly high.
• Stage IIC – the cancer has spread to nearby lymph nodes and is larger than 5 cm. Tumour markers are normal or slightly high.
• Stage IIIA – the cancer has spread to distant lymph nodes and/or the lungs. Tumour markers are normal or slightly high.
• Stage IIIB – the cancer has spread to distant lymph nodes and/or the lungs but not to other organs. At least one tumour marker is substantially higher than normal.
• Stage IIIC – the cancer has spread to distant lymph nodes and/or the lungs and at least one tumour marker is very high. Alternatively, the cancer has spread to distant areas of the body other than the lymph nodes or lungs.