Limitations of CT scanning in Bosniak staging of renal cystic carcinoma

Abstract

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.

Figure 1:

(A and B) Represent contrast and non-contrast enhanced CT scans from 2014 of the left upper pole cyst when it was noted that the patient complained of 6 months of weight loss. The CT findings indicated the upper pole cyst to still be classified as Bosniak stage IIF. There is no notable calcification, septations or convincing solid components. (C and D) Both represent the MRI of the upper pole cyst. The findings images demonstrate extensive, thick septations in the upper pole cyst upgrading the cyst to Bosniak stage III. The scans outline the limitations of surveillance CT vs MRI to stage the severity of renal cystic disease in this patient.

Figure 2:

Bosniak classification of renal cystic lesions [4].