Cancer of the testicle (also called the testis), a rare kind of cancer in men,
is a disease in which cancerous (malignant) cells develop in the tissues of
one or both testicles. There are two testicles located inside of the scrotum
(the sac of loose skin that lies directly under the penis). Sperm and male hormones
are made in the testicles.
There are three main types of testicular tumors, which develop in different
types of cells in the testicles. The most common type, called a germ cell tumor,
develops in the germ cells, the cells that produce sperm cells. About 90 percent
of testicular tumors are germ cell tumors.
Stromal cell tumors are much less common; they are cancers that start in the
hormone-producing cells in the testicles. There are several different subtypes
of germ cell and stromal cell tumors. A third type of testicular tumor, called
a secondary testicular tumor, is a tumor that results from cancer that has started
elsewhere in the body. Many of these tumors begin as lymphoma, particularly
in men over the age of 50.