A 14 year old girl having 10-days lumbar pain, polaquiuria and moderate pain to palpation is reported. Blood and urine analysis were normal. Abdominal ultrasound scan showed cavity free and solid, rounded, heterogeneous, intrapelvic mass compressing bladder and uterus. Magnetic resonance image was performed showing right gonad compromise with extensive liver and sacro-lumbar spine invasion. Tumoral markers were ruled out. During surgery, primary tumor mass localizad in the right gonad was completely excised. Melanotic peritoneal and hepatic disemination were observed. The patient had left streak gonad and infantile uterus (2 x 3 cm). As gonad dysgenesia was suspected, high resolution cromosomic study was performed and resulted in cariotype 46 XY. Microscopy of the resected gonad showed primary gonad melanoma. Chemotherapy was instituted with no tumor response and the patient died two month later.