A 39-year-old woman with no relevant personal history presented with left flank pain.
Physical examination revealed a large mass in the lumbar region.
Abdominal ultrasound described a retroperitoneal mass of 15 x 8 cm. The A.C.T. revealed a large left retroperitoneal mass, compressing the kidney and seemed to be in front of the renal bifurcation and component dependent on the pelvis.
No signs of insanity.
With no surgical contraindication it was decided to remove the mass, intraoperatively a large retroperitoneal mass was observed that included left kidney with cystic component, complete excision of the mass was performed together with inevitable left nephrectomy.
Macroscopic anatomy was described at the level of the lower renal pole neoformation of 20 x 14 x 9 cm with solid and cystic component.
Electron microscopy confirmed mucinous cystic teratoma with solid areas of neuronal tumor transformation and with the rest of the renal parenchyma without other particularities, the positivity for chromogranin synovium in this tumor.
The subsequent evolution after three years of follow-up was satisfactory and the patient was completely asymptomatic.
