From the case: Diagram - Bosniak classification of renal cysts
Category II cysts are almost universally benign, but unlike type I they may contain thin septa. Thin or slightly thickened calcification may be noted within the cyst wall. Minimal but un-measureable enhancement of the septa or cyst wall may also be appreciated. High-attenuation cysts of than 3 cm in diameter that do not enhance are considered type II.