Bosniak classification for Renal Cyst

Applicable to US, CT or MR imaging.

	Features	Management
Bosniak I	Anechoic cyst Thin walled No septa, calcification, solid components No contrast enhancement	No intervention required	Class 1 Renal cyst
Bosniak II	Hairline-thin septa Fine calcification / Short thick calcification No contrast enhancement	No intervention required	Class 2 Renal Cyst Class 2. Notice the faint thin septa? Also a smaller simple cyst in the lower pole.
Bosniak IIF	Multiple hairline-thin septae +/- minimal thickening Minimal wall thickening Thick / Nodular calcification No soft tissue component	Needs follow-up
Bosniak III	Thick wall / septa, irregular / smooth	Needs surgical intervention	Class 3. Notice the thicker septa and larger size of the cyst? Class 3 Renal Cyst
Bosniak IV	Bosniak III + soft tissue component which enhances.	Clearly malignant