Xylene in Histology Laboratories

Study Notes

Xylene is a colorless clearing agent used for clearing, embedding, and mounting procedures in histology laboratories.
It takes 1/2 to 1 hour for clearing and is suitable for most routine histologic processing schedules of less than 24 hours and tissue block sizes less than 5 mm in thickness.
Xylene is reasonably cost-effective and effective for short-term clearing of small tissue blocks.

It is used as a clearing agent during tissue processing and as a dewaxing agent during staining.
Xylene is also used in cover slipping, cleaning tissue processors, as a solvent to remove synthetic immersion oil from microscope objectives, and in recycling used slides.

It is the most rapid clearing agent, clearing tissues within 15-30 minutes, making it suitable for urgent biopsies.
Xylene makes tissues transparent and is miscible with absolute alcohol and paraffin.
It does not extract out aniline dyes and does not dissolve celloidin, making it suitable for celloidin sections.
Xylene evaporates quickly in paraffin oven and can be readily replaced by wax during impregnation and embedding.
It is a relatively cheap clearing agent.

Xylene is highly inflammable and requires special handling and storage procedures.
If used longer than 3 hours, it makes tissues excessively hard and brittle.
It causes considerable hardening and shrinkage of tissues, making it unsuitable for nervous tissues and lymph nodes.
Xylene becomes milky when an incompletely dehydrated tissue is immersed in it.
It can irritate eyes, nose, and respiratory tract, and can cause dermatitis if absorbed through the skin.

Keep containers tightly closed to prevent xylene from subliming and entering the atmosphere.
Use non-sparking tools to handle xylene, and store it in a cool and dry area away from incompatible substances.
Store xylene in a flammable liquid storage cabinet, and wash hands thoroughly after handling.
Remove contaminated clothing and wash before reuse, and keep away from heat, sparks, and flames.