MLHG 106 - Introduction to Histology and Cytology: Lesson 2 Q&A Flashcards

100 QA-style flashcards covering grossing, processing, decalcification, embedding, microtomy, cryostat, safety, and equipment concepts from the notes.

What is Grossing in histology and when is it performed?

Grossing is the macroscopic evaluation and description of a tissue specimen after fixation, completed by a Pathology Assistant or Pathologist and includes patient name, assigned number, surgical procedure, tissue size, weight, colour, consistency, and any abnormalities; margins may be inked.

Who typically performs the grossing procedure?

A Pathology Assistant or a Pathologist performs grossing and dictates the gross description.

What information is documented during grossing regarding the patient and specimen?

Patient name, assigned number, surgical procedure, tissue size, tissue weight, tissue colour, tissue consistency, and observed abnormalities.

What instrument is used to measure tissue size during grossing?

A plastic ruler is used to measure tissue size.

What is done to margins if suspect tumors or malignancies are observed during grossing?

Ink is used to mark margins or suspicious areas.

What happens to the tissue after grossing and before processing?

The tissue has already been fixed before grossing and then proceeds to processing after the gross description is completed.

What are tissue cassettes and what are they used for?

Plastic containers with perforations and tight lids used to hold tissue pieces during processing and embedding.

Why do tissue cassettes have perforations?

Perforations allow processing reagents to completely immerse the tissue for proper dehydration and infiltration.

What colour-coded cassette example indicates neuro tissue?

Yellow indicates neuro tissue.

What colour-coded cassette is typically used for biopsies?

Green is commonly used for biopsies.

Which cassette colour is associated with autopsies?

Blue is used for autopsies.

What does the white cassette colour usually represent?

White represents other tissues, such as lung and similar tissues.

Is cassette colour-coding universal across all labs?

No, color-coding is not universal and may vary by institution.

What happens to specimens not suitable for processing?

They are accessioned, described, given the notation 'no section taken,' stored for a designated period per institutional policy.

What is the purpose of automatic cassette labelling?

To label cassettes automatically and ensure traceability through processing via the LIS.

Why must numbering be accurate throughout processing?

Errors in numbering can lead to incorrect or missed diagnoses and serious patient consequences.

Name a key piece of grossing equipment you might find in a grossing station.

Dissecting board.

What is the purpose of a dissecting board in grossing?

To hold and stabilize tissue during gross dissection and cutting.

What is the typical tool used to slice tissue during grossing?

A scalpel or dissection knife.

Why might a grossing station require a triple beam or analytical balance?

To weigh tissue samples accurately for documentation.

What is the role of India ink in grossing?

India ink or similar ink is used to mark margins or lesions for documentation.

What is the primary purpose of a fixation step in histology?

To preserve tissue structure and elements for subsequent processing and microscopy.

What is decalcification used for in histology?

To remove calcium from calcified tissues like bone so that paraffin sections can be prepared and microscopic elements preserved.

What are the risks of over-decalcification?

Tissue distortion and poor staining.

Why must tissue be well fixed before decalcification?

Improper fixation enhances tissue damage during decalcification and can be four times worse without proper fixation.

Name one common decalcifying agent that is slow-acting and gentle on tissue.

Formic acid (5-25%) is a slow, gentle decalcifying agent.

Name a fast decalcifying agent used in histology.

Strong inorganic acids such as nitric acid or hydrochloric acid.

What is EDTA used for in decalcification?

EDTA is a chelating agent that binds calcium and decalcifies very gently and slowly.

What is a common endpoint determination method for decalcification?

Probing for pliability, X-ray to check calcium removal, and chemical tests for residual calcium.

What is the sequence of tissue processing steps?

Dehydration, Clearing, Wax Impregnation (Infiltration) with paraffin.

What is the purpose of dehydration in tissue processing?

To remove water from tissue using increasing concentrations of alcohol.

Which solvent is used for clearing after dehydration?

Xylene or other clearing agents.

What is the purpose of paraffin wax impregnation in tissue processing?

To infiltrate tissue with wax so that thin sections can be cut and mounted for sectioning.

What is the typical melting point range for paraffin wax used in embedding?

Approximately 40-70°C.

What additive helps reduce crystal size and improve adhesion in paraffin wax?

Beeswax and other additives like resin or plastic polymers.

What is paraplast and why is it used in embedding?

Paraplast is a mixture of purified paraffin and plastic polymers that provides elasticity and enables easier cutting of tough tissues.

What is the typical embedding temperature for paraffin during infiltration?

Paraffin is heated to about 56°C to 60°C.

Why should alcohol dehydration typically be done in 3-4 changes of absolute ethanol?

To ensure complete water removal and minimize tissue distortion.

What clearing agents are commonly used in histology?

Xylene, toluene, chloroform, cedar wood oil, Gooding and Stewart Fluid, Van Ebner’s Fluid, and EDTA in various forms.

What does xylene do to tissue during clearing?

Raises the tissue’s refractive index and clears tissue by making it more transparent.

What hazard is associated with xylene that requires ventilation and PPE?

Xylene is toxic and volatile; exposure can irritate eyes, nose, skin, and throat and may cause systemic effects.

Why is ventilation important when using clearing agents like xylene?

To prevent inhalation of toxic fumes and reduce risk of exposure.

What is paraplast’s melting point and its advantage in embedding?

Melting point around 56°C; offers elasticity and stronger support for sectioning, including bone.

What is an automatic tissue processor and what is its goal?

An automated machine that performs dehydration, clearing, and paraffin infiltration; goal is complete water removal and embedding in paraffin.

What is the difference between open and closed system tissue processors?

Open systems move cassettes between reagents with exposure to air; closed systems keep cassettes enclosed to minimize fumes and cross-contamination.

What is the advantage of a fluid exchange automatic processor?

Tissue remains stationary while reagents move; reduces air exposure, minimizes fumes, allows maximum drainage and minimizes carryover.

What safety practice is essential when operating an automated tissue processor?

Use an emergency power supply or UPS, monitor reagents, and maintain good ventilation.

What is a key safety consideration for reagents used in tissue processing?

They can be flammable or toxic (e.g., alcohol, acetone, xylene, toluene); handle with PPE and fume hood.

What is the purpose of embedding center checks before leaving the lab?

To ensure all settings and supplies (hot plate, wax, molds, forceps, etc.) are in place for safe processing the next day.

In embedding, what should be ensured about tissue orientation in the mold?

Tissue should be centered, with a wax margin, and the long axis aligned parallel to the mold edge.

What is the benefit of using a suitable mold size during embedding?

Prevents tissue from touching mold edges and facilitates proper sectioning.

Why is cross-contamination a concern during embedding?

Contamination from one block to another can cause diagnostic errors; practices minimize this risk.

How should you handle cassettes to prevent cross-contamination during embedding?

Open only one cassette at a time and handle with clean tools; avoid fragments escaping.

What is a common risk if embedding molds are not cleaned regularly?

Cross-contamination and artifacts in tissue sections.

What is the purpose of keeping embedding molds clean and wiping with gauze?

To prevent contamination and residue from previous specimens affecting new blocks.

What is the role of embedding temperatures in block quality?

Correct temperature ensures proper wax infiltration and solidification; overheating can cause damage.

What can happen if embedding temperatures are too high?

Block overheating, distortion, and potential tissue damage in sections.

What should be checked regularly on the embedding center hot plate?

Temperature to prevent damage to tissue due to excessive heat.

What is a common embedding problem and its potential result?

Mold too small or tissue floating can cause poor embedding and distorted blocks.

What is the purpose of a safety check before leaving the embedding area?

To verify proper on/off status, mold availability, and essential embedding supplies.

What is microtomy?

The process of cutting thin sections (3-5 microns) of paraffin-embedded tissue using a microtome.

What thickness are typical microtomy sections?

About 3-5 micrometers for routine histology.

Where are the sections placed after cutting by the microtome?

They are floated onto a 40-45°C water bath and then placed on labeled slides.

What is the typical slide drying temperature for mounting sections?

Slides are dried at 58-62°C for 20-30 minutes.

What is the purpose of warming the water bath to 40-45°C in microtomy?

To allow tissue ribbons to spread flat and separate into individual sections.

What is a cryostat used for in histology?

A microtome placed inside a freezer used for frozen section histology.

What temperature range is typical for a cryostat's chamber?

Usually -20 to -30°C, though some protocols vary.

What PPE considerations are important when using a cryostat?

Always wear PPE; if TB is suspected, disinfect the cryostat.

What is the anti-roll plate used for in cryosectioning?

To help sections stay flat and prevent curling during sectioning.

What is a key precaution when handling unfixed tissue in frozen sectioning?

Treat tissue as potentially infectious and follow appropriate biosafety measures.

Why should you not float sections from multiple blocks at once?

Mixing sections from different cases can cause misidentification and diagnostic confusion.

What temperature should flotation bath water be relative to the wax melt point?

Approximately 4-5°C below the melting point of the wax.

What can happen if sections stay on the flotation bath too long?

The wax may melt and sections can over-expand, causing tissue damage.

How should sections be drained before drying on slides?

Sections should be drained briefly, either vertically or horizontally, to prevent wrinkling.

What issue can arise from overheating during slide drying?

Nuclear meltdown characterized by uneven, distorted, or poorly stained nuclei.

What is a common consequence of poor dehydration or improper clearing in microtomy?

Tissue sections may crumble, appear opaque, or be difficult to cut.

What is a typical problem related to water in the flotation bath?

Contaminants can transfer to sections causing artifacts or contamination.

Why is slide cleanliness important in microtomy?

Dirty slides can introduce contaminants that spoil a good section and staining.

What is one major cause of cross-contamination on the flotation bath?

Not skimming the water surface between specimens or leaving sections floating together.

What is a recommended practice to avoid cross-contamination between blocks?

Skim the water surface between specimens and avoid leaving multiple blocks floating.

What factor influences tissue section quality during microtomy?

Block temperature, knife sharpness, and embedding quality.

What might be a sign of over-processing in tissue blocks seen during microtomy?

Hard, brittle blocks or excessive shrinkage.

What is a typical problem with the knife edge that can affect sectioning?

Dull knife edge or nicks on the knife that cause tearing or poor sections.

Why is it important to check the knife and instrument alignment in microtomy?

To ensure clean, consistent ribbons and prevent section artifacts.

What is a common cause of ribbon curling during microtomy?

A dull knife or improper knife clearance angle.

What is a ribbon in microtomy?

A continuous strand of successive tissue sections cut and collected on the water bath.

What is the purpose of using Histofreeze spray or ice on the tissue surface before sectioning?

To improve flatness and reduce wrinkles in tissue sections.

What is the importance of using a fresh blade in microtomy?

A fresh blade reduces tissue tearing and produces cleaner sections.

What is the purpose of a 40-45°C water bath in microtomy?

To float and flatten the tissue ribbons before mounting onto slides.

What steps follow embedding before microtomy?

Block trimming to expose a full cross-section, then cutting and producing a ribbon.

What is the purpose of embedding temperature checks in embedding center?

To prevent overheating that damages tissue sections.

What is meant by ‘cross-contamination’ in embedding and how can it be prevented?

Transfer of tissue between blocks; prevented by careful handling and segregation of specimens.

What is the typical function of a microtome handle?

To move the block holder up and down and advance the specimen over the knife.

What is a common sign of improper fixation during microtomy?

Soft mushy blocks and sections that crumble.

What is wax penetration and why is it important?

Wax infiltration replaces clearing reagent with molten paraffin to embed tissue firmly for sectioning.

Why is water bath cleanliness critical in microtomy?

To prevent debris and artifacts from contaminating sections.

What is the consequence of not using an anti-roll plate in cryostat sectioning?

Sections may curl or not lay flat, compromising accuracy.

What is the role of the pararffin wax in embedding blocks?

To provide a solid medium for thin sectioning and mounting on slides.

What does ‘dehydration’ mean in histology?

Removal of water from tissue using graded alcohols.

What does ‘clearing’ entail in tissue processing?

Removal of dehydrating agents and replacement with a solvent compatible with paraffin.