Tissue Preparation · Histology

Before staining with an aqueous dye like Hematoxylin, what must be done to a paraffin-embedded section on a slide?

  1. It must be dehydrated in 100% ethanol
  2. It must be coated with a second layer of wax
  3. It must be heated to 100 degrees Celsius
  4. It must be deparaffinized and rehydrated
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Correct answer: It must be deparaffinized and rehydrated

Most stains are water-based and cannot penetrate the hydrophobic paraffin wax. Sections must first be washed in xylene to remove the wax and then passed through decreasing concentrations of alcohol to introduce water back into the tissue.

Difficulty: Medium Question 10 of 20

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