Cryosurgery is a blind therapeutic method for which it is not possible routinely to remove destroyed tissue for histologic examination. Therefore, some questions have to be answered in doing cryosurgery: The first question is the diagnosis of the lesion to be treated. This can be done invasively by making a biopsy before cryosurgery or after the first freezing cycle. The next question is the extent and invasion depth of a tumor, and the last question is the extent and depth of cryonecrosis. Only if these problems are solved is cryosurgery a controlled therapeutic instrument. For these reasons we have tried to find an objective measurement for determining the depth of invasion and the internal structure of a tumor. After 8 years of experience with this method, we can now say that the diagnostic ultrasound is a noninvasive method that allows the determination of the in vivo invasion depth of skin tumors very exactly, and additionally gives some information about the in vivo architectural pattern of the tumor. By this information, freezing time and thus cryonecrosis can be exactly adjusted to invasion depth of the tumors.1-3. © 1990.
