Fig. 14

Schematization of Bosniak’s classification for cystic renal masses and associated malignancy rate. Bosniak I: hairline-thin wall without septa, calcifications, or solid components; malignancy rate of 0%. Bosniak II: few hairline-thin septa, fine calcifications in a short segment of the wall, or slightly thickened calcification; malignancy rate of 0%. Bosniak IIF: multiple hairline-thin septa, smooth minimal thickening of the wall or septa, and thick or nodular calcifications; malignancy rate of 5%. Bosniak III: thickened irregular wall or septa with enhancement after the administration of contrast agent; malignancy rate of 50–70%. Bosniak IV: soft tissue enhancing mass independent of the wall or septa; malignancy rate of 95–100%. Remember that Bosniak I–II cysts do not need follow-up, Bosniak IIF cysts need follow-up, and surgery is indicated for Bosniak III–IV cysts