Objective: To report a case of a 46,XX male with an intratubular undifferentiated germ cell neoplasia within an extra-abdominal gonad.

Design: Case report.

Setting: Molecular, cytogenetic, pathologic, and clinical units of three tertiary hospitals.

Patient(s): A male with ambiguous genitalia at birth and descended testes observed in a pediatric endocrinology setting.

Intervention(s): Physical examination, hormonal assays, cytogenetic investigation, molecular analysis, surgical intervention for biopsies and bilateral orchiectomy, and pathologic evaluation.

Main outcome measure(s): Pathologic evaluation with immunostaining for placental alkaline phosphatase and C-kit.

Result(s): Conventional chromosome analysis revealed a 46,XXq- karyotype, and fluorescence in situ hybridization experiments with the SRY probe found a signal at the short arm of the deleted X chromosome. Molecular analysis indicated the presence of a portion of the short arm of the Y chromosome including the proto-oncogene TSPY. Pathologic evaluation of the gonads revealed an intratubular undifferentiated germ cell neoplasia.

Conclusion(s): This is the first case of a 46,XX male with descended testes in whom an intratubular undifferentiated germ cell neoplasia developed. When proposals of management in this subgroup of disorders of sexual differentiation are formulated, the risk of germ cell malignancy must be taken into account.