It's not clear what causes testicular cancer in most cases. Doctors know that testicular cancer occurs when healthy cells in a testicle become altered. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But sometimes some cells develop abnormalities, causing this growth to get out of control — these cancer cells continue dividing even when new cells aren't needed. The accumulating cells form a mass in the testicle.

Nearly all testicular cancers begin in the germ cells — the cells in the testicles that produce immature sperm. What causes germ cells to become abnormal and develop into cancer isn't known.

Oct. 15, 2011

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