Intratubular germ cell neoplasia (carcinoma in situ): a preinvasive lesion of the testis.

The existence of a preinvasive lesion of the testis, referred to as intratubular germ cell neoplasia or carcinoma in situ, is now well established. The finding has been made in infertile males with various types of testicular abnormalities. In a number of cases, there has been subsequent progression to typical malignant germ cell tumors, including seminoma and embryonal carcinoma. Light and electron microscopic studies indicate that the abnormal germ cells within the seminiferous tubules resemble germ cells at early stages of differentiation. The cells lack intercellular connections characteristic of normal developing germ cells, but otherwise are similar to gonocytes and prespermatogonia in the fetal and prepubertal testis.