Specimen Handling & Fixation Flashcards

Which fixative is MOST likely to cause the formation of formalin pigment (formol heme) artifact?

Answer: Unbuffered formalin in contact with blood-rich tissue

Formalin pigment forms when unbuffered (acidic) formalin reacts with hemoglobin in blood-rich tissues, producing brown-black granular deposits.

A histotechnician notices mercury pigment deposits in a tissue section. Which fixative was MOST likely used?

Answer: Zenker's or B-5 fixative

Mercury-containing fixatives (Zenker's and B-5) leave brown mercury pigment deposits that must be removed with iodine followed by sodium thiosulfate before staining.

For optimal immunohistochemical (IHC) results, the RECOMMENDED cold ischemia time before fixation is:

Answer: Less than 1 hour

CAP/ASCO guidelines recommend less than 1 hour of cold ischemia time to preserve antigen integrity for IHC, especially for hormone receptors.

Which fixative BEST preserves lipids for histochemical demonstration?

Answer: Osmium tetroxide

Osmium tetroxide fixes and stains lipids simultaneously by reacting with unsaturated fatty acids, making it the fixative of choice for lipid preservation.

A specimen is received in formalin but appears to have been fixed for only 2 hours. What is the MOST appropriate action?

Answer: Continue fixation to achieve adequate penetration before processing

Under-fixed tissue will not process properly and will show poor morphology; continuing fixation until adequate penetration is achieved is essential.

Which statement about B-5 fixative is MOST accurate?

Answer: It is excellent for lymphoid and bone marrow biopsies due to superior nuclear detail

B-5 fixative (mercuric chloride and formalin) provides excellent nuclear detail in lymphoid tissue and bone marrow biopsies, though it requires mercury waste disposal.

What is the PRIMARY reason tissues should NOT be allowed to freeze during transport in cold conditions?

Answer: Ice crystal formation disrupts cellular architecture causing freezing artifact

Ice crystals that form during freezing expand and physically rupture cell membranes and disrupt tissue architecture, creating freezing artifact in histologic sections.