Germ cell neoplasia in situ (GCNIS) in a cryptorchid testis. Cryptorchidism increases the risk for testicular germ cell tumors by 3.5 to 5 fold as compared to a control population. About 2% to 8% of patients with cryptorchidism have GCNIS. About 50% of these patients will develop germ cell tumor (seminoma >> non-seminomatous) within 5 years if left untreated. Orchipexy is recommended between 6 months and 18 months of age to reduce the risk.
In unilateral cryptorchidism, the non-cryptorchid testis is also at a slightly higher risk of developing germ cell tumors. The most common subtype of GCNIS is the unclassified variety. The tubules contain atypical germ cells with clear cytoplasm (due to glycogen content). The basement membrane is hyalinized and thickened.