Testicular cancer. Coloured ultrasound scan of a cancer (blue, upper centre) of the testis. Testicular cancer is rare, mainly affecting young to middle-aged men. It most often appears as a firm, painless swelling of one testis. Treatment usually involves the surgical removal of the testis (orchidectomy), along with chemotherapy if there is a risk that the cancer has spread. However, the prognosis is very good, especially if the cancer is detected early in its development. Ultrasound images are produced from the reflections of high-frequency sound waves off internal body structures.