Limitations of CT scanning in Bosniak staging of renal cystic carcinoma

The Bosniak Classification is used to quantify the risk of malignancy and need for observation or radical treatment based on the findings of computed tomography (CT). The case described is that of a 65-year-old man with renal cystic disease who was initially given a Bosniak stage IIF classification and was subsequently managed with CT surveillance. CT surveillance showed increased cyst size in the left kidney with cystic changes, however, the Bosniak classification remained the same. It was not until the patient deteriorated further that an MRI was indicated. The MRI findings upgraded the lesion from Bosniak IIF to Bosniak III. As a result, the patient underwent a radical left nephrectomy and a biopsy, which revealed clear cell carcinoma. This case argues the limitations of the Bosniak classification and the value of using MRI at an earlier stage, especially with unusual circumstances such as a chronic history of enlarging cysts.