What is the primary purpose of the clearing step in tissue processing?

• A. Remove alcohol from tissues prior to wax infiltration.
• B. Infiltrate with wax.
• C. Decalcify tissues.
• D. Stain tissues.

Answer: (A)

The main idea here is that clearing prepares the tissue for embedding by replacing the dehydrating alcohol with a solvent that mixes with paraffin. After dehydration, the tissue is saturated with alcohol; the clearing agent (such as xylene) displaces that alcohol and makes the tissue compatible with molten paraffin. This step ensures the wax can infiltrate the tissue properly to provide a solid block for sectioning. Decalcification is a separate treatment for hard tissues, and staining happens after embedding and sectioning, not during clearing.