Pathological Sciences: Tissue Processing Lecture 3

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Questions and Answers

Which step comes after Fixation in the routine tissue processing?

Impregnation

Tissue selection and description

Specimen collection, transportation and receipt

Dehydration (correct)

What is the aim of the Paraffin Technique in routine tissue processing?

To mount sections on a slide

To examine H&E stained slides under the light microscope

To prepare tissues in a supporting medium ready to be cut into thin sections (correct)

To fix specimen in a supporting medium

What is the first step in the steps from specimen to report?

Specimen disposal

Specimen collection, transportation and receipt

Fixation (correct)

Tissue embedding

In tissue processing, what follows Impregnation?

Tissue embedding Signup and view all the answers

What is the last step in routine tissue processing?

Block & Slide archiving Signup and view all the answers

What instrument is used for cutting FFPE blocks?

Microtome Signup and view all the answers

What is the embedding medium of choice for routine specimens?

Paraffin wax Signup and view all the answers

What is the purpose of the clearing reagent in tissue processing?

To act as a link between the dehydrator and wax Signup and view all the answers

Which reagent is used in routine practice as a dehydrating solution?

Isopropyl alcohol Signup and view all the answers

What is the main drawback of industrial methylated spirit (IMS)?

It is harmful by inhalation and if swallowed Signup and view all the answers

What should be done if Xylene waste is produced?

Dispose of it as specialist waste Signup and view all the answers

How are tissue processing schedules validated?

By using surplus clinical material not required for diagnosis Signup and view all the answers

What is the role of the intermediary steps in paraffin processing?

To transfer tissue through different chemical solutions Signup and view all the answers

What are the characteristics of paraffin wax that make it suitable for tissue processing?

It has a consistency very similar to that of the tissue itself and it can support the cutting of thin sections Signup and view all the answers

What is the most likely result of insufficient tissue fixation and formalin penetration?

Incomplete processing affecting overall morphology, chromatin detail, tissue integrity Signup and view all the answers

What is the typical color of formalin pigment seen in a formalin-fixed paraffin section of kidney?

Brown to black Signup and view all the answers

What can be used to replace xylene in the processing of specimens?

Isopropyl alcohol in combination with ethanol Signup and view all the answers

What is required for processing fatty tissues?

Extended time and increased temperature Signup and view all the answers

What has improved, allowing for an increase in the number of larger tissue blocks processed to meet reporting demands?

Improved processing equipment Signup and view all the answers

What is the embedding medium typically used for routine specimens in tissue processing?

Paraffin wax Signup and view all the answers

What is the purpose of hard tissue pre-treatment in tissue embedding process?

To de-calcify the tissue Signup and view all the answers

What is the aim of using a cold plate in the tissue embedding process?

To aid in tissue orientation in the mould Signup and view all the answers

Which automated stainer and coverslipper is mentioned in the text?

Sakura Automated Stainer and coverslipper Signup and view all the answers

What is the purpose of block checking in the quality assurance process?

To record case number and number of blocks before processing Signup and view all the answers

What comes after fixation in the steps from specimen to report?

Tissue processing Signup and view all the answers

What is the typical thickness of routine sections in microtomy?

3-4 microns Signup and view all the answers

What is the main drawback of industrial methylated spirit (IMS) mentioned in the text?

Strong odor Signup and view all the answers

What is the role of intermediary steps in paraffin processing according to the text?

To maintain tissue shape during processing Signup and view all the answers

What instrument is used for cutting FFPE blocks according to the text?

Manual Sakura Signup and view all the answers

What is done if Xylene waste is produced according to the text?

Treat it as hazardous waste Signup and view all the answers

Study Notes

Tissue Processing Steps

After fixation, the next step is dehydration in routine tissue processing.
The first step from specimen to report is fixation.
Following impregnation in tissue processing, the embedding step occurs.
The last step in routine tissue processing is microtomy, where tissue is sliced for examination.

Paraffin Technique and Its Purpose

The aim of the Paraffin Technique is to preserve histological architecture for accurate microscopic analysis.
Paraffin wax is the embedding medium of choice for routine specimens due to its ability to infiltrate tissue thoroughly.

Instruments and Reagents

A microtome is the instrument used for cutting formalin-fixed paraffin-embedded (FFPE) blocks.
Industrial methylated spirit (IMS) is commonly used as a dehydrating solution, but its main drawback is toxicity.
Clearing reagents, such as xylene, are used to remove alcohol from tissue before embedding; alternatives to xylene include limonene and other solvents.

Handling and Validation

If xylene waste is produced, it should be disposed of according to hazardous waste regulations to prevent environmental harm.
Tissue processing schedules must be validated to ensure optimal outcomes through consistent methodologies.

Fatty Tissue Processing

Processing fatty tissues requires specialized techniques due to their unique composition, which may involve additional embedding agents.

Quality Assurance

Block checking is essential in the quality assurance process, ensuring that adequate samples are prepared for diagnostics.
The intermediary steps in paraffin processing play a critical role in ensuring the tissue is properly prepared for embedding, enhancing preservation quality.

Characteristics and Effects

The characteristics of paraffin wax, such as melting point, clarity, and compatibility with staining techniques, make it highly suitable for tissue processing.
Insufficient fixation and formalin penetration can lead to poor tissue preservation, resulting in artifact formation and diagnostic challenges.

Sections and Thickness

The typical thickness of routine sections in microtomy is around 4 to 5 micrometers.

Cold Plates and Hard Tissue

The aim of using a cold plate in the tissue embedding process is to facilitate rapid solidification of the embedding medium, improving morphology preservation.
Hard tissue pre-treatment is vital for ensuring complete infiltration of the embedding medium, especially for denser tissues.

Automation in Processing

Advances in automation have increased the capability for processing larger tissue blocks, helping meet the growing demands for laboratory reporting.

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Description

Learn about tissue processing, embedding, microtomy, staining, and quality assurance in the field of pathological sciences. Explore the principles, practices, and reagents used in tissue processing, as well as the techniques for embedding and cutting blocks using a microtome.