[Germ cell tumour and pseudohermaphroditism. Histological and cytogenetic study (author's transl)].

The case report is that of a 15 years old boy presenting with unilateral undescended testis and hypospadias. Surgical exploration disclosed an absence of regression of the Müllerian system and an intra-abdominal gonad replaced by a seminoma. There are arguments to suspect that the seminoma arose from a gonadoblastoma controlateral testis biopsy disclosed a germ cell abnormality consistent with an in situ neoplastic transformation. It is emphasized that all forms of cryptorchidism must be explored surgically and that apparently normal gonads left in place in cases of unilateral gonadic dysgenesis, must be attended with extreme care.