OBJECTIVE Intratubular germ cell neoplasia is a precursor to testicular germ cell cancer. The condition is characterized by large germ cells with large nuclei with a hyperchromatic, coarse chromatin pattern, large prominent nucleoli and abundant pale cytoplasm. In prepubertal boys these cells are located centrally and peripherally mixed with normal cells in the seminiferous tubules. We evaluated the impact of adult intratubular germ cell neoplasia marking immunohistochemistry in screening for intratubular germ cell neoplasia in boys with cryptorchidism. METHODS Histology sections of 236 testicular biopsies were retrieved from 170 boys 1 month to 15 years old operated on for cryptorchidism (excluding disorders of sex development). Specimens were incubated with primary antibodies, including anti-placental-like alkaline phosphatase, anti-Oct3/4, anti-C-kit and anti-D2-40 receptor. RESULTS A 1-year, 1-month-old boy had intratubular germ cell neoplasia and all positive markers. The prevalence of placental-like alkaline phosphatase positive staining of germ cells in testicular biopsies was 98% in boys younger than 1 year, 82% in those 1 to less than 2 years old, 74% in those 2 to less than 3 years old and 60% in those 3 to 15 years. Similarly the prevalence of C-kit positive staining was 71% in boys younger than 1 year, 49% in those 1 to less than 2 years, 16% in those 2 to less than 3 years and 34% in those 3 to 15 years. Placental-like alkaline phosphatase negative germ cells did not express any of the other described antigens. In none of the 116 testes from boys older than 1 year and 7 months were any Oct3/4 or D2-40 positive germ cells identified. Up to that age 33% and 8% of biopsies were Oct3/4 and D2-40 positive, respectively. CONCLUSIONS Adult intratubular germ cell neoplasia/cancer immunohistochemical markers cannot be used alone for intratubular germ cell neoplasia screening in male infants with cryptorchidism because positive immunohistochemistry is commonly seen within this age group, when most orchiopexies are performed. It is generally not plausible that intratubular germ cell neoplasia originates during fetal development in patients with cryptorchidism.