Testicular cancer. Coloured transmission electron micrograph (TEM) of a seminoma cancer in tissue from a testis (testicle). Seminomas are malignant (cancerous) tumours that tend to spread to lymph nodes via the lymphatic system. They are the most common form of testicular cancer and occur most often in men between the age of 30 to 45 years. It is a malignant neoplasm and is one of the most treatable and curable cancers, with a survival rate above 95% if discovered in early stages. Here the large characteristic tumour cells can be seen with much smaller white blood cells also present. Human tissue. Magnification: x1000 when printed at 10 centimetres wide.