Histological section: Difference between revisions

It has been suggested that Bread_loafing be merged into this article. (Discuss)

It has been suggested that this article be merged into Histology. (Discuss)

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Histological section refers to thin slices of tissue applied to a microscopic slide, usually around 5 to 10 micrometres thick, which are viewed under a microscope. For further discussion of histological section and staining methods, one should review histology article.

The specimen is cut into the correct size and configuration prior to fixation and microtome cutting. The specimen is stained and positioned for proper orientation. With Mohs surgery, the specimen is cut in a manner to allow mounting all of the surgical margins on one plane. With standard bread loafing, the specimen is usually cut into multiple sections with the surgical margin stained. Some technologist will stain the edge to be oriented toward the microtome. The cut specimen is then transferred directly to frozen medium for frozen section processing, or placed in small cassettes for dehydration and paraffin embedding.

Fixation is done either by the fixed tissue method with paraffin, or by frozen section. With fixed tissue method, the tissue specimen is preserve in either formaldehyde or an acidic solution until it is processed. The tissue is then removed from the preservative, dehydrated with multiple solvent baths, and fixed in hot liquid parafin. The hardened parafin block with the fixed tissue is then cut with the microtome. With frozen tissue sectioning, the tissue is immediately frozen prior to processing (frozen section).

The frozen tissue block embedded in a frozen cutting medium, or the paraffin fixed tissue is cut using a very fine knife called a microtome. A cryostat is a micotome mounted inside a freezer for processing frozen tissue.

The frozen thin slices of tissue are mounted on a warm glass slide at room temperature, or the paraffin embedded slides are mounted on a heated glass. This allow them to be stained and ready for staining. The tissue mounted slides are then dry in open air or in a drying oven.

Multiple stain baths are used to make the tissue more visible to the naked eye. Please see histology for discussion of the stains used. Sections usually have a very thin piece of glass applied over the surface called a cover slip. The glass cover slip is glued onto the slide with a special optical grade transparent glue.

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