The Specimen Tissue is preserved with a fixative. The most widely used fixative for pathologic histology is formaldehyde. Tissue should be fixed as promptly as possible after removal and cessation of blood circulation. Fixation deactivates these enzymes and stabilizes protein structures.
Proper processing is the key to subsequent successful examination of sections under the microscope.
Processing to paraffin wax is the most commonly used technique when sections of tissue are wanted for diagnosis. Commonly used sectioning methods require infiltration with imbedding material, such as paraffin wax. Fixed tissues are impregnated with paraffin before sections are cut This entire process takes place in automatic tissue processors. The wax block containing impregnated tissue is melted, the tissue piece or pieces are oriented for sectioning, and the block is allowed to solidify. Thin strips of tissue, no more than several cells thick, are cut from the blocks on a microtome by skilled technicians.