Tissue Processing & Fixation Flashcards

During tissue processing, the graded alcohol series typically ends at which concentration before clearing?

Answer: 100% (absolute) ethanol

Tissue must pass through 100% (absolute) ethanol as the final dehydration step to ensure complete water removal before the clearing agent is introduced.

What is the optimal paraffin infiltration temperature range used in automated tissue processors?

Answer: 50–60°C

Paraffin infiltration is performed at 50–60°C, just above the melting point of standard embedding paraffin, ensuring the wax remains liquid for infiltration without damaging tissue.

A tissue specimen shows shrinkage artifact and poor nuclear detail after processing. The most likely cause is:

Answer: Excessive dehydration time in high-concentration alcohol

Prolonged exposure to high-concentration alcohol causes protein denaturation and excessive tissue shrinkage, resulting in poor morphology and nuclear detail.

Which embedding medium is used for frozen sections when rapid diagnosis is required?

Answer: Optimal cutting temperature (OCT) compound

OCT compound is the standard embedding medium for frozen sections because it provides support for cryostat cutting at low temperatures without requiring chemical processing.

The fixative Bouin's solution is best suited for which type of tissue?

Answer: Testicular and gastrointestinal biopsies

Bouin's solution (picric acid, formalin, acetic acid) is preferred for testicular and gastrointestinal biopsies because it provides excellent nuclear detail and cytoplasmic preservation.

Tissue that has undergone autolysis prior to fixation will most likely show:

Answer: Ghost outlines of cells with loss of nuclear detail

Autolysis causes enzymatic self-digestion of cellular components, resulting in ghost outlines, karyolysis, and loss of nuclear and cytoplasmic detail in H&E sections.

The term 'cold ischemia time' in tissue handling refers to:

Answer: Time from tissue removal to placement in fixative

Cold ischemia time is the interval between surgical removal of tissue and placement in fixative; minimizing this time reduces autolysis and preserves nucleic acids for molecular testing.