Introduction to Histology and Cytology -Lesson 1 NOTES & Flashcards

What are the three main branches of anatomic pathology?

Pathology (study of disease, usually cancer); Cytopathology (cell-based diagnosis); Histopathology (examination of tissue)

What is Cytopathology?

Diagnosis based on characteristics of cells

What is Histopathology?

Examination of pieces of tissue under a microscope to diagnose disease

What is the foundation of both histology and cytology labs?

Assessment of morphologic features of cells or tissues

Who plays a key role in preparing specimens for pathologists?

Medical laboratory technicians

Name two common specimen preparation steps.

Staining and cover slipping (also accessioning and filing as part of prep)

What does accessioning a specimen involve?

Receiving samples and assigning accession numbers

What is specimen rejection?

Rejecting a specimen due to issues like labeling errors or missing requisitions

What does WHMIS legislation govern in histology labs?

Labels, dates, storage and disposal of hazardous solutions

How should sharps be handled in histology labs?

Proper handling and disposal according to safety procedures

What is spill containment in histology labs?

Procedures for containment and clean-up of hazardous spills

How should histology lab emergencies be addressed?

Recognize and respond to lab emergencies or incidents

What is ergonomics in the histology workplace?

the practice of designing the work environment, equipment, and job tasks to fit the worker, minimizing work-related musculoskeletal disorders (MSDs) like back pain, and enhancing comfort, efficiency, and quality

What is Histology?

The diagnosis and study of diseases of tissues, examined under a microscope

What is Cytology?

Diagnosis based on characteristics of cells

What is Histopathology?

The examination of tissue pieces under a microscope to diagnose disease

What is the relationship between histology and cytology?

Both assess morphologic features of cells or tissues

Who prepares samples for the pathologist?

The histotechnologist

What types of specimens are processed in histology?

Surgical and autopsy specimens

What sizes can histology specimens vary in?

Small tissue biopsies, amputations, large partial organs

What thickness are tissue samples mounted on slides?

3–5 micrometers

What does FFPE stand for?

Formalin-fixed paraffin-embedded

What is the purpose of special stains?

To highlight particular cell morphology

Where are histology samples prepared?

In the histology laboratory

What is the role of the histotechnologist?

Prepares samples for the pathologist to examine

What are the main steps in tissue processing?

Fixation, dehydration, clearing, infiltration, embedding

What is fixation?

Preservation of tissue by stopping biological processes and stabilizing structure

What is ischemic time?

Time from tissue removal until it is placed in fixative

What fixative-to-tissue ratio is recommended?

20:1 (fixative volume to tissue volume)

What is the rate of fixation?

About 1 mm per hour

Which tissues fix more slowly?

Dense and fatty tissues; tissues with capsules

What effect does a capsule have on fixation?

Slows fixative penetration, requiring longer fixation

What are chemical fixation methods?

use chemicals called fixatives to preserve cells and tissues by chemically stabilizing their components, like proteins and lipids, preventing degradation and maintaining cellular structure

What are physical fixation methods?

Heating, microwaving, cryo-preservation

When should tissues be fixed after removal?

Immediately after surgical removal or arrival in lab

What pH range is important for fixation, especially for ultrastructure?

pH 7.2–7.4

Why is fixation important?

Preserves structure, stops autolysis and putrefaction, hardens tissue, aids staining

What are the three fixative reaction categories explained?

Additive vs non-additive; coagulant vs non-coagulant; tolerant vs intolerant

What is a coagulant fixative?

a histological substance, such as ethanol or picric acid, that preserves tissue by denaturing and precipitating proteins into a permeable meshwork

What is a non-coagulant fixative?

Forms a light precipitate with less shrinkage

What are primary fixing agents listed for histology?

Formaldehyde, potassium dichromate, mercuric chloride, ethanol, picric acid, acetic acid, osmium tetroxide, glutaraldehyde

What is the most common fixative in histopathology labs?

10% neutral buffered formalin (NBF)

What is formalin chemically?

A solution of formaldehyde in water (about 37–40% formaldehyde)

What is the advantage of formalin?

Tolerant fixative with good penetration; inexpensive; suitable for nervous system

What is a disadvantage of formalin?

Irritating fumes; carcinogenic; can cause dermatitis

What is formalin pigment?

Acid hematin pigment formed when formalin becomes acidic

How can formalin pigment be removed?

Alcoholic, picric acid, or alkaline alcohol

What is the preparation of 10% neutral buffered formalin?

900 ml water, 3.5 g NaH2PO4, 6.5 g Na2HPO4, 100 ml formalin

What hazard does formaldehyde pose in the lab?

Irritation, dermatitis, and respiratory hazards; use a fume hood

Why is formalin called a universal fixative?

Widely used, good penetration, tolerant, affordable

What is paraformaldehyde in relation to formalin?

A white precipitate formed when formaldehyde polymerizes; filtered to remove

What is a common alternative fixative containing mercuric chloride?

Zenker's fluid

What is Bouin's fluid used for?

Fixative containing picric acid; good for glycogen demonstration; rapid penetration

What is a disadvantage of Bouin's fluid?

Picric acid is explosive when dry; tissues become hard and brittle

What is Brasil's alcoholic picro-formal fixative used for?

Routine fixative for surgical specimens; good for glycogen; similar to Bouin's

Why should you refer to SDS for reagents?

To understand safe handling and toxic ingredients

How should fixatives be stored?

In original containers, cool and dark; keep solids wet; 15–20x tissue volume

What does a specimen’s requisition include?

Patient name, date, tissue type, site, physician and location

What is a surgical number used for?

A unique identifier used on requisition, containers, cassettes, slides, and reports

What is specimen rejection policy?

A written policy detailing rejection criteria and procedures

Give an example of a reason for specimen rejection.

Labeling errors

Give another example of a reason for specimen rejection.

Missing, incomplete or incorrect requisition

Give another example of a reason for specimen rejection.

Incorrect type of fixative or insufficient fixative

What is a STAT specimen's typical turnaround time?

1 hour (for STAT priority)

What is the priority order for histology specimens?

1) Emergency Department NOW; 2) STAT (1 hour); 3) ASAP (4 hours); 4) Routine (~24 hours)

What does TAT stand for?

Turn Around Time from receipt to results

How should fresh specimens be delivered to the lab?

Without delay and with temperature control (ideally refrigerated)

Is temperature control more critical for fixed or unfixed specimens?

Fresh/unfixed specimens require temperature control; fixed specimens are less critical

What packaging requirements apply to transporting biological materials under TDG Act?

Rigid leak-proof container, absorbent material, leak-proof secondary container, outer container

What should you do with dry ice during packaging?

Do not seal dry ice in the sealed secondary container; place it between the plastic container and outer bag

What are two common ways histology specimens are received?

Fixed specimens in a closed jar with fixative or unfixed specimens wrapped in saline-soaked towels for STAT processing

What is a tissue cassette used for?

A small container that holds tissue during processing

What is the purpose of embedding tissue in paraffin?

To create a solid block for sectioning

What is FFPE (Formalin-Fixed, Paraffin-Embedded) block used for?

To cut thin sections for slide mounting and microscopic analysis

What does H&E stand for and why is it used?

Hematoxylin and Eosin; used to stain slides for histological analysis

What is a rotary microtome used for?

To cut paraffin-embedded tissue into thin sections

What is the typical temperature for cutting paraffin sections?

58–60°C

What is the difference between fixed and unfixed specimens regarding processing?

Fixed specimens are already in fixative; unfixed require rapid placement into fixative for STAT processing

What is a requisition’s role in proper labeling?

Provides necessary patient and specimen details to ensure correct labeling

What does 3-5 μm refer to in histology?

Thickness of tissue sections mounted on slides

What does IHC stand for?

Immunohistochemistry

Why are special stains used in histology?

To highlight specific cell morphology or tissue components

What does a pathologist rely on after processing slides?

Stained slides for microscopic evaluation

What is the main purpose of fixation?

Preserve tissue structure and stop enzymatic/autolytic processes

What happens if autolysis is not stopped timely?

Decomposition of tissue due to enzymatic activity

What is paraffin used for in histology?

To embed tissue for cutting into thin sections

What is dehyrdation in tissue processing?

Removal of water from tissue using increasing concentrations of alcohol

What is clearing in tissue processing?

Use of a clearing agent (e.g., xylene) to prepare tissue for infiltration

What is infiltration in tissue processing?

Penetration of tissue with paraffin wax

What is embedding in histology processing?

Encasing tissue in paraffin to form an FFPE block

What is the role of the histology laboratory tour and YouTube videos mentioned?

Supplementary learning resources for lab setup and workflow

What is the key reason to correctly document safety incidents in the lab?

To apply safety measures and prevent recurrence

What is the impact of poor fixation on staining quality?

Leads to variable staining and poor tissue morphology

What is the responsibility of the medical laboratory assistant regarding reagents?

Prepare common reagents and refer to procedures; follow SDS for safety

What is the main goal of histology sample processing?

Provide pathologist with stained tissue slides for microscopic evaluation

What is the significance of 4°C storage for tissue?

Used to refrigerate non-fixed specimens or materials awaiting fixation

What does 'gross to micro' imply in histology?

Starting from macroscopic specimen description to microscopic tissue analysis

What is a fixed specimen's transport consideration compared to unfixed?

Fixed specimens tolerate transport better; unfixed require rapid handling

What is a 'surgical number' used on cassettes and slides?

The surgical number identifies the specimen across all processing steps

What is the role of 'accumulation log' in accessioning?

Daily record of accession numbers assigned to specimens