Histopathology Flashcards
What does a histopathologist do
Examines tissues
Examines biopsies,resections,frozen sections and post mortens
Biopsy
A small section of tissue taken from patient and placed in formalin to preserve it by cross-linking proteins
Then they’re embedded in wax to allow v thin sections (2-3μm thick) to be cut using a microtome which are mounted on a glass microscope for further prep then analysis
Checks of tissue I’d normal inflamed or cancerous
Tales 2-3 days
Resection
Taken from tissue removed as part of a surgical procedure and can be processed same a biopsy
Are used to look at the stage of a disease
Takes 5-7 days for result to reach clinician
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Frozen sections
Taken during surgical procedures and examined by pathologists in real time while patient is being operated on
Freshly taken tissue frozen by a machine called a cryostat, cut then mounted on glass slides and stained like with biopsies
Can give rapid diagnosis in minutes which can be relayed back to surgeon to inform the surgery- 30 mins usually
e.g. is tissue cancerous? Has all the cancerous tissue been removed? Are there any other pathological processes going on?
What two conditions must be me for frozen sections to be me
Fresh
Free of preservatives
What tissue type can be donated to bio banks and used to inform genomic studies
Resections
Cytopathologists
Examines cells
Can use fine needle aspirates
Fine needle aspirates
Fine needles can be used to suck out (aspirate) cells from a lesion to be analysed as a smear- needle can penetrate relatively inaccessible tissues e.g. thyroid nodule and assess the suspect mass without need for surgery (non-surgical technique)
When can histopatholgy and cytopathology be used together
Kaposis sarcomas
Antibody conjugations
Things we attach to Fc region of antibodies to make them useful in diagnosis
Enzymes eg peroxidase and alkaline phosphatase
Fluorescent probes allow measure T of levels of molecules in a sample can also do multiplexing via using several antibodies with different flurophorrd
Magnetic beads allows purification of cell types
Drugs eg kadcyla an anti HER2 antibodies linked to chemical emtansine
Direct defection
Where conjugate attached to antibody which detects an antigen we’re looking for- called the primary antibody
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Indirect detection
Primary antibody is bound to antigen but is unconjugated. A secondary conjugated antibody is used that binds to the primary antibody
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Use of manufactured antibodies
- Immunoassays → e.g. detection of hormones by circulating antibodies
- Immunodiagnosis e.g. presence of circulating antibodies in infectious diseases, IgE
- Blood group serology
ELISA
Enzyme linked immunosorbent assay
- Clinical samples adhere to plastic plate
- Probe with specific antibody raised against the molecule of interest
- Enzyme conjugation generates a coloured product
- Refer to standard curve to determine precise concs of the molecule in the sample
Flow cytometry
Allows detection of specific cells, notably lymphocytes
You have fluorescently conjugated antibodies specific for leukocyte antigens (normally surface antigens) but of different colours
You run a stream of single cells through a laser beam(s) which excites fluorphores
Colour of light emitted and the forward or side scatter of laser beam denotes the identity of the cell surface molecules expressed and the size and granularity of the cells
examples of antibodies used are:
- anti-CD3+ on T cells (pan T cell marker)
- anti-CD4+ on T helper cells
- anti-CD8+ on cytotoxic T cells
- anti-CD19+ on B cells
- anti-CD56+ on Natural killer (NK) cells
