The Bosniak classification system is based on CT findings to classify renal cysts into 5 categories to predict the possibility of malignancy.
Bosniak classification of renal cysts
Bosniak classification
Characteristics
Examination
I
Simple benign cysts with thin walls, no septa, no calcification or solid components Same density as water, not enhanced by contrast
benign
II
benign cyst may be associated with very thin septa, calcification may be present in the wall or septa, uniform high attenuation lesion <75px in diameter, smooth margins without enhancement< span="">
benign
IIF
May contain more dilute septa, with minimal contrast enhancement of the dilute septa and the bursal wall, slight thickening of the septa and bursal wall, and the bursa may contain foci of calcification, nodular in shape, without contrast enhancement. Soft tissue elements without contrast enhancement are included within this category as well as completely provincial. No enhancement. Highly attenuated renal lesions ≥75px with generally good margins
with follow-up observation.
Some are malignant
III
Indeterminate masses within the capsule with irregular thickening of the capsule wall or septum and contrast enhancement
Surgically treated or actively observed, more than 50% are malignant
IV
Obviously malignant containing contrast-enhancing soft tissue component
Surgically treated, mostly malignant