Histological Artifacts · Histology

Which artifact appears as dark, needle-like brown crystals, often occurring when the pH of the fixative falls below 6.0?

  1. Mercury pigment
  2. Chrome pigment
  3. Formalin pigment
  4. Melanin deposits
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Correct answer: Formalin pigment

Acid formaldehyde hematin forms when acidic formalin reacts with hemoglobin. It is a common artifact in blood-rich tissues and can be prevented by using 10% neutral buffered formalin.

Difficulty: Medium Question 3 of 20

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