Update on the pathology of testicular tumors.

At least 90% of testicular tumors belong to the group of germ cell tumors (GCTs), which are classified according to the 2004 World Health Organization (WHO) classification. Race is one of the most important etiologic factors in the development of GCTs. White men living in Western industrialized countries show the highest rates of incidence. Known risk factors are cryptorchidism, contralateral GCT, familial association, infertility, testicular atrophy, trauma, surgery, socioeconomic status, environmental factors, and occupational exposure to noxious conditions. For the most part, the morphology of GCTs is well known to pathologists. There are, however, some little-known rare entities like anaplastic type of spermatocytic seminoma. In the group of nonseminomatous GCTs are emerging the somatic-type malignancies (carcinomas, sarcomas) arising in teratomas. Tumors of sex cord/gonadal stroma account for 1.6-6% of adult testicular tumors and are somewhat more frequent in children. Absolutely nothing is known about the epidemiology, histogenesis, and possible etiology of these tumors, which derive from Leydig, Sertoli, granulosa, and theca cells. In the group of "miscellaneous tumors," lymphomas are the most frequent testicular tumors in men older than age 50.