Histopathology is the microscopic examination of biological tissues to observe the appearance of diseased cells and tissues in very fine detail.
Samples for histopathology must be processed and fixed for examination. Two processes are used. The first is a chemical fixation procedure in which the tissue samples are immersed in a bath of paraffin, or wax, over a 12- to 16-hour period. This allows the tissue to be sliced into two to seven micrometer sections for examination.
The second process used is frozen sectioning. Tissue samples are frozen and sliced thin, as in the chemical fixation process. Frozen sectioning is quicker, although these samples are of lesser quality than the chemical fixation samples. Typically, frozen section is used to determine the borders, or edges, of a tumor while surgery is being performed.