Initially, an enlargement of the scrotum is often the only symptom of the growth. This is unfortunate, because the patient tends not to go to the doctor unless it is causing pain. By then, however, metastasis has often occurred. An operation is the best means of determining whether a cancer is present. If a growth is discovered, the testicle is removed at once and the tumour is examined under a microscope to determine its cellular composition and whether or not it is malignant. Cellular composition is important, because the various cancers of the testis differ in their tendency to form metastases, and also in how they respond to different therapies.