What are neoplasms in situ?

➢ Most testicular tumors in postpubertal males arise from germ cell neoplasia in situ. ➢ This precursor lesion is present in conditions associated with a high risk for developing germ cell tumors (e.g., cryptorchidism, dysgenetic gonads) ➢ Exhibits the same abnormality of chromosome 12 that is characteristic of fully developed germ cell tumors. ➢ Often found in “normal” testis adjacent to full-blown germ cell tumors.