#Cryotherapy to a malignancy (such as superficial basal cell carcinoma) is a different process than treatment of an #actinic keratosis. An iceball needs to form at the site of malignancy and the surrounding tissue for a good 30 seconds (I always count it in my head). After the ice ball thaws, the process is repeated. It's a painful procedure (I always use local #anasthesia), healing takes a few weeks and is often associated with a contracted #scar. For these reasons it's not so commonly employed these days.