Specimen Handling & Fixation Flashcards

Which fixative is MOST appropriate for preserving glycogen in tissue sections?

Answer: Bouin's fixative

Bouin's fixative (picric acid, formalin, acetic acid) preserves glycogen well and is commonly used for this purpose.

A biopsy specimen arrives in the lab after a 6-hour delay without fixative. What is the MOST likely consequence?

Answer: Autolytic tissue degradation

Without fixation, endogenous enzymes continue to digest cellular components, leading to autolysis and loss of tissue architecture.

The recommended tissue-to-fixative volume ratio for optimal formalin fixation is:

Answer: 1:10

A minimum 1:10 tissue-to-formalin ratio ensures adequate fixative penetration and complete fixation.

Which of the following BEST describes the mechanism of formalin fixation?

Answer: Cross-linking of amino groups via methylene bridges

Formaldehyde reacts with amino groups on proteins to form methylene bridges, creating cross-links that stabilize tissue structure.

Which fixative is CONTRAINDICATED when performing acid-fast staining for mycobacteria?

Answer: Zenker's fixative

Zenker's fixative contains mercuric chloride, which can interfere with acid-fast staining results and requires extra processing steps.

What is the PRIMARY advantage of using glutaraldehyde as a fixative for electron microscopy?

Answer: Superior ultrastructural preservation

Glutaraldehyde's bifunctional aldehyde groups create extensive cross-links that preserve ultrastructure for electron microscopy better than other fixatives.

When receiving a lymph node specimen for lymphoma workup, which handling protocol is MOST important?

Answer: Submit fresh tissue for flow cytometry before fixation

Lymphoma workup requires fresh tissue for flow cytometry, cytogenetics, and molecular studies, so a portion must be submitted fresh before any fixation.