Lecture 3 Tissue dissection Flashcards
What is a specimen dissection?
The selection of tissue from a sample that will be used to make wax blocks
What is the step by step basic process of tissue dissection?
- Check the pot and request card details match
- Give sample a unique identifying number
- Enter specimen on to the LIMS system
- Describe and dissect the specimen
What are the 3 main features to be looked for when diagnosing a tumour?
- Any associated lymph nodes
- Resection margins
- Tumour itself
Name different types of tissue dissection samples
- Biopsies
- Excisions
- Resections
Biopsies are often linked to resections so if a biopsy is taken then a resection would most likely be taken as well
What is a core needle biopsy (CNB)?
A needle is inserted to extract tissue which is laid out flat and straight on sponge so that it can be embedded and sectioned easily.
The sponge allows reaction with the reagent.
What is an excision?
Removal of a piece of tissue without removing the entire organ
What are some of the issues to consider when carrying out tissue dissection?
- Infection risk specimens - TB/HIV/HepC - More fixation time is needed for many more hours to kill of infectious agents
- Sampling for molecular studies
List the health and Safety precautions for tissue dissection
- PPE
- Vaccinations - needed before working in grossing rooms, chilling rooms and trimming rooms
- Correct use of knives
- Disinfection
- Extraction - The vapour created from formalin is extremely hazardous as it is a class 1 carcinogen
- Reagents: Fixatives
Health and safety protocols for Clinical governance?
- Ensure all identifiers match (form, pot, cassettes)
- Never handle more than one specimen on the bench at once - e.g. do not want to transfer cancer cells to lymph node sample as patient would be given unnecessary chemotherapy.
- Board and instruments cleaned between each specimen
Key considerations when doing tissue dissection
- Kind of specimen
- What are clinical details - For example, if one has obtained a cancer resection, it is going to be treated very differently to some one who has a colorectal resection for someone who has diverticular disease because the pathologies are different.
- Is the specimen fixed?
- Does specimen require orientation?
- Does the specimen require inking?
- How will specimen be dissected?
- What procedures are to be requested?
What is the list of information on the request form?
Nature of the specimen?
Surgical procedure?
Significance of any orientation?
Clinical presentation For example, particularly for skin, a clinician’s perspective of a tissue that has just had fresh blood supply would be different to a histopathologist. Another example - patients with fairer skin would have lesions disappear into skin and are not able to be found.
Patient history including any tests results - For example, normally a benign resection does not require sampling of surrounding lymph nodes but for a patient that has a history of cancer, it is needed.
‘Aiding fixation’ involves 3 different things:
- Slicing e.g. breast, uteri, kidney
- Inflating e.g. oesophagus, stomach, lung, bladder
- opening e.g. bowel specimens
What is tissue processing?
Process of removing water from tissue and replacing it with wax.
This is to form a rigid structure to allow thin sectioning of the tissue
What is the process of tissue processing?
- Dehydration
- Clearing
- Impregnation
The tissue is taken through a gradient of alcohols, xylenes and wax’s. Gradients get progressively stronger throughout process. Otherwise, cells would be destroyed.
What are the steps of embedding step by step?
- Open cassette
- Select mould
- Fill bottom of cassette with molten wax
- Place Tissue in Mould and Orientate (orientation depends on what kind of tissue it is, what is being looked for and what consultants is looking for)
- Place cassette on cold plate to anchor
- Top up with molten wax
- Lie on cold plate until solid
