How do we differentiate between benign and renal cyst?

The differentiation between a benign   renal cyst and a cystic RCC remains one of the more common and difficult problems in   renal imaging. Bosniak has developed a useful classification scheme that divides renal cystic lesions into four categories that are distinct from one another in terms of the likelihood of malignancy This radiological differentiation is based on the CTscan findings or MRI (regularity of the wall of the cyst presence or absence of calcifications, septations, enhancement more than 20 housefield unit after IVcontrast)