The frozen section procedure is a pathological laboratory procedure to perform rapid microscopic analysis of a specimen. It is used most often in oncological surgery. The technical name for this procedure is cryosection. The microtome device that cold cuts thin blocks of frozen tissue is called a cryotome. The quality of the slides produced by frozen section is of lower quality than formalin fixed paraffin embedded tissue processing. While diagnosis can be rendered in many cases, fixed tissue processing is preferred in many conditions for more accurate diagnosis. The intraoperative consultation is the name given to the whole intervention by the pathologist, which includes not only frozen section but also gross evaluation of the specimen, examination of cytology preparations taken on the specimen (e.g. touch imprints), and aliquoting of the specimen for special studies (e.g. molecular pathology techniques, flow cytometry). The report given by the pathologist is often limited to a "benign" or "malignant" diagnosis, and communicated to the surgeon operating via intercom. When operating on a previously confirmed malignancy, the main purpose of the pathologist is to inform the surgeon if the resection margin is clear of residual cancer, or if residual cancer is present at the resection margin. The method of processing is usually done with the bread loafing technique. But margin controlled surgery (CCPDMA) can be performed using a variety of tissue cutting and mounting methods, including Mohs surgery. History The frozen section procedure as practiced today in medical laboratories is based on the description by Dr Louis B. Wilson in 1905. Wilson developed the technique from earlier reports at the request of Dr William Mayo, surgeon and one of the founders of the Mayo Clinic Earlier reports by Dr Thomas S. Cullen at Johns Hopkins Hospital in Baltimore also involved frozen section, but only after formalin fixation, and pathologist Dr William Welch, also at Hopkins, experimented with Cullen's procedure but without clinical consequences. Hence, Wilson is generally credited with truly pioneering the procedure (Gal & Cagle, 2005). Procedure The key instrument for cryosection is the cryostat, which is essentially a microtome inside a freezer. The microtome can be compared to a very accurate "deli" slicer, capable of slicing sections as thin as 1 micrometre. The usual histology slice is cut at 5 to 10 micrometres. The surgical specimen is placed on a metal tissue disc which is then secured in a chuck and frozen rapidly to