Viralization due to Leydig cell tumor diagnosis by magnetic resonance imaging. Case management report.

A 3-year-old boy who presented with signs of virilization had a Leydig cell tumor of the left testis that could not be detected by physical examination or by high resolution ultrasonography. His very small tumor was demonstrated by magnetic resonance imaging. The implications of adding this sensitive method of imaging to the evaluation of prepubertal virilization of presumed testicular etiology are discussed.