HISTOPATH: CLEARING

It is the process whereby alcohol or a dehydrating agent is removed from the tissue and replaced with a substance that will dissolve the wax which the tissue is to be impregnated or the medium on which the tissue is to be mounted

• Clearing
• De-alcoholization

The tissue has a ________ appearance during Clearing

• translucent
• blue
• off white

Clearing fluids with a low boiling point are generally more readily replaced by melted paraffin

• TRUE
• FALSE

Characteristics of a Good Clearing Agent:

• Miscible with alcohol/ Makes tissues transparent
• Miscible with and easily removed by melted paraffin wax and/or by mounting medium
• Should not produce excessive shrinkage, hardening or damage of tissue
• Does not dissolve out aniline dyes
• Does not evaporate quickly in a water bath

Most commonly used ▪ generally suitable for routine histologic processing schedules of less than 24 hours▪ most rapid clearing agent ▪ clears within 15-30 minutes

• Xylene (Xylol)
• Toluene
• Benzene
• Chloroform

May be used as a substitute for xylene or benzene ▪ clears within 1-2 hours ▪ recommended for routine purposes

• Xylene (Xylol)
• Toluene
• Benzene
• Chloroform

Recommended for urgent biopsies (15-60 minutes) and routine purposes ▪ damages the bone marrow

• Xylene (Xylol)
• Toluene
• Benzene
• Chloroform

Recommended for tough tissues (skin, fibroid and decalcified tissues), for nervous tissues, lymph nodes and embryos ▪ suitable for large tissue specimens

• Xylene (Xylol)
• Toluene
• Benzene
• Chloroform

Used to clear both paraffin and celloidin sections ▪ recommened for central nervous system tissues and cytological studies (smooth muscles and skin) ▪ clearing is completed in 2-3 days

• Cedarwood oil
• Aniline oil
• Clove oil
• Carbon tetrachloride
• Methyl Benzoate and Methyl Salicylate

Recommened for clearing embryos, insects, and very delicate specimens

• Cedarwood oil
• Aniline oil
• Clove oil
• Carbon tetrachloride
• Methyl Benzoate and Methyl Salicylate