E-module: Histopathology Flashcards
What does a histopathologist do?
Deals with tissues
Examine sections, noting architecture of tissues, asks what it tells us about a particular condition
What does a cytopathologist do?
Deals with cells
Often responsible for taking cells from patients, preparing for examination and then delivering expert diagnosis on cell sample
What tissue samples might a histopathologist work with?
Biopsies
Resection specimens
Frozen sections
Post motte season
What are biopsies?
Small sections of tissues removed from patient and placed in formalin solution.
What is the purpose of formalin solution?
To preserve tissues by cross-linking proteins
Why are biopsies embedded in paraffin wax?
To allow very thin sections (2-3um thick) to be cut instrutments known as microtome
What sort of questions can microscopic examination of a biopsy tell us?
- is tissue normal?
- is tissue inflamed and if so what is cause?
- is the tissue cancerous and if so what type of cancer?
What are biopsies primarily used for?
To make diagnoses e.g. is there a need for surgery
Where are resection specimens taken from?
Tissue that has been removed as part of a surgical procedure - they can be processed as for a biopsy
What are resections primarily used for?
To look at the stage of a disease
What else can be done with tissue from resection specimens?
can also be donated to biobanks and used to inform genomic studies of the disease process, with the input of other medical professionals such as immunologists and microbiologists.
When are frozen sections taken?
During surgical procedures
What happens to make frozen tissue?
Freshly taken tissue is frozen by a machine known as a cryostat, cut then mounted on glass slides and stained as for biopsies
What can frozen tissue do?
Provide a rapid diagnosis in minutes which can be relayed back to surgeon to inform surgery e.g.
- is tissue cancerous
- has all cancerous tissue been removed
- is there another pathological process going on
What timescales are involved between a histopathology lab and clinicians?
Frozen section - 30 mins
Biopsies - 2 to 3 days
Resection specimen - 5 to 7 days
How can cells be collected for analysis?
- fine needle - can be used to get into a lesion and suck out (aspirate) the cells which can then be analysed
What is an advantage of fine needle aspirarates?
It is a powerful technique as needle can penetrate relatively inaccessible tissues e.g. thyroid nodule
- assess suspect mass w/o need for surgery
What is the downside of fine needle aspirarates?
Cytopathologist is only looking at cells and unable to comment upon likely architecture of tissue
Give an example of how histopathology and cytopathology can be combined and work together.
Kaposi’s sarcoma (a relatively rare cancer) has a skin biopsy which shows spindly looking cells penetrating collagen fibres and an antibody recognising the endothelial cell marker CD31 (typical of endothelial cells) which allows us to define this biopsy as an endothelial cell tumour.
If these biopsies are combined w/fine needle aspirate taken from enlarged lymph nodes then a diagnosis of reactive lymphadenopathy can be given due to the mixed cell population observed.
What can high levels of circulating antibodies recognising double stranded DNA be associated with?
Systemic lupus erythematosus (SLE)
Sjögren’s syndrome
Rheumatoid arthritis
How can antibodies be manufactured to be used to detect specific molecules in immunohistochemistry?
Attachments are added to the Fc region of the antibody (a.k.a conjugations)
What sort of attachments can be added to manufactured antibodies?
- enzymes e.g. peroxidase, alkaline phosphate w/ colourless substrate to give coloured product
- fluorescent probes allow rapid measurement of molecule levels within a sample
- magnetic beads e.g. purification of cell types
- drugs
What is a main property of antibodies that allows them to be used as diagnostic tools?
Unique specificity for target antigens
What scenarios can manufactured antibodies be used for?
- blood group serology
- immunoassays
- immunodiagnosis
