A 61-year-old male patient was referred to our clinic for an incidental ultrasound finding of a renal mass following a study of epigastralgia.
His personal history included cholelithiasis and right hydrocelectomy. In the anamnesis, the patient did not report pain in the renal fossa, haematuria, episodes of urinary infection, asthenia, anorexia or weight loss. Physical examination revealed no abdominal masses or megaliths.
Ultrasound showed an exophytic nodule measuring 4 x 2 cm in diameter at the level of the upper pole of the right kidney with solid and cystic areas, with vascularised areas (Doppler ultrasound). Given the diagnosis of a complex renal mass, an abdomino-pelvic CT scan was requested, which showed a complex cystic lesion at renal level, and it was impossible to definitively determine its benign nature. We performed an abdominal MRI which identified the mass measuring 4.2 x 3.3 x 3 cm, hypointense in T1 sequences and markedly hyperintense in T2 sequences, with several linear septa inside, linear enhancement of the walls of the cyst and the internal septa after administering gadolinium, making it diagnostic of a minimally complicated cystic mass.

Given the diagnostic uncertainty of the CT scan and the ultrasound findings (Bosniak grade III renal cyst), we decided to perform a surgical exploration and by means of an incision in the flank we performed a lumpectomy.
Subsequent evolution was satisfactory and the histological study confirmed the presence of a Fuhrman grade I multilocular cystic clear cell renal cell carcinoma, with negative resection margins.
In the control CT scan 6 months after the operation, we can observe the post-surgical changes at the level of the renal cortex and adjacent fat, with no evidence of local recurrence. The patient is currently asymptomatic, being reviewed every 6 months with ultrasound and annually with CT.

