Intra-Operative Diagnosis

It is sometimes necessary to make a dignosis during the time of an operation. In such a case we perform a procedure known as a "frozen section". The surgeon sends a sample of tissue to the laboratory. Usually the surgeon either needs a diagnosis (Is it cancer or is it something else?) or they already know the diagnosis and need to know if they have removed everything (Have I sent you a sample with clear excision margins?). In these instances the sample of tissue is measured and described in the usual way but instead of being processed to paraffin wax, it is now frozen over a few seconds using compressed carbon dioxide gas or a high efficiency electrically operated refrigeration device. In either case, the tissue is frozen to about -60蚓 before further treatment.

If the material was not frozen in a cryostat it will probably be transferred to one at this point. A cryostat (interior pictured right) is a microtome in a deep freeze. The fact that the tissue is frozen allows us to cut fairly thin sections from the sample, around twice the thickness of a paraffin section (8痠). The slides can then be stained by the H&E method in urgent cases - or kept frozen for research projects. The pathologist can expect to see the results of a frozen section in less than 20 minutes... usually much less... around 5 minutes.