75-year-old woman with a history of obstructive pulmonary disease, hypertension and hypercholesterolemia.
She consulted our department due to the incidental ultrasound finding of a renal lesion.
Ultrasound: complex cystic lesion, multiseptate, with polylobulated contours, 11 cm in diameter and with peripheral punctate calcifications, occupying almost the entire kidney.
Abdominal-pelvic CT scan: left renal lesion 11 x 7 cm in diameter, multiseptate and with punctate calcifications. Absence of retroperitoneal adenopathy.

A differential diagnosis was made between cystic multilocular nephroma, as a first option, and cystic renal cell carcinoma.
We performed an isotopic renogram with Tc-99m. Left kidney with lower uptake and functionalism, with a cold central image that could correspond to an occupying lesion. I.R. function: 25%.
Bone scintigraphy: No alterations.
With the diagnosis of Bosniak III renal lesion, surgical intervention was decided and a nephrectomy was performed.
Pathology report: multilocular cystic nephroma, without atypia.
