Malignant germ cell tumor in situ in a cryptorchid testis.

A case of a malignant undifferentiated germ cell tumor in situ of an undescended testis diagnosed by needle biopsy is described. Four similar cases have been so far recorded in the literature, all of them in the infertile men with normally descended descended testes. Two of them developed embryonal carcinoma of testis 4 1/2 later and one had a concomitant seminoma. In a high-risk group of patients (atrophic testis, cryptorchidism), a needle biopsy of a testicle may discover malignancy in its very early phase of development (Stage 0), at which time an orchiectomy alone may be a curative treatment.