2.16 - Histopathology Flashcards
1
Q
What does a histopathologist do?
A
- deals with tissues - examine sections, noting the architecture of the tissue and asking what it tells us about a particular condition
- useful for diagnosis and to determine the efficacy of a treatment
- deals with a variety of tissue samples: biopsies, resection specimens, frozen sections, post-mortems
- real-time examination can inform the surgical process
2
Q
What is a biopsy?
A
- a small section of tissue removed from a patient
- preserved in a formalin solution which cross-links proteins and fixes the tissue
- embedded in paraffin wax to allow very thin sections (2-3um) to be cut using a microtome
- mounted on glass microscope slide for further preparation prior to analysis
- used to see whether the tissue is normal/inflamed/cancerous, and what the likely cause is
- takes 2-3 days for a result from the histopathology lab to reach the clinician
3
Q
What different stains are used and for what?
A
- haematoxylin and eosin (H&E) staining used to identify nuclei and cytoplasmic granules of leukocytes in tissues
- Ziehl-Neelsen stain used to identify acid-fast bacteria as it stains them red - aids in diagnosing TB
- Congo red - ECM components e.g. elastin and collagen
- oil red O - lipids
4
Q
What is a resection specimen?
A
- taken from tissue that has been removed as part of a surgical procedure and can be processed the same as a biopsy
- used primarily to look at the stage a disease is at
- e.g. has the cancer penetrated / metastasised?
- has all cancerous tissue been removed or is chemotherapy needed?
- can be donated to biobanks to be used in genetic studies of the disease process
- takes 5-7 days for result to reach clinician
5
Q
What is a frozen section?
A
- taken during surgical procedures and examined by pathologists in real time during the operation
- freshly taken tissue is frozen by a cryostat, cut, mounted on slides and stained as for biopsies
- rapid diagnosis in minutes (around 30 minutes) which can be relayed back to surgeon to inform the surgery
- e.g. is the tissue cancerous? has all the cancerous tissue been removed? are there any other pathological processes going on?
- not all processes are compatible with initial preparation of sample e.g. tissue for frozen sections must be fresh and free of preservatives like formalin
6
Q
What do cytopathologists do?
A
- deals with cells - take cells from patient, prepare them for examination + deliver their expert diagnosis on the cell sample
- cells collected, smeared on glass slide, stained, examined
7
Q
What are fine needle aspirates?
A
- fine needle inserted into lesion and sucks out (aspirates) cells to be analysed as a smear
- +: needle can penetrate relatively inaccessible tissues e.g. thyroid nodule and assess a condition without need for surgery
- -: looks at cells in isolation - no information regarding tissue architecture
8
Q
What is an example of where histopathology and cytopathology can be used together?
A
- Kaposi’s sarcoma is a relatively rare cancer and often indicative of immunodeficiency
- skin biopsy shows spindly looking cells penetrating collagen fibres
- immunochemistry can be used to identify endothelial cell marker CD31 on surface of endothelial cells using an antibody (brown = CD31 expressed) - allows us to define this next biopsy as an endothelial cell tumour
- biopsies combined with fine needle aspirate taken from patient’s enlarged lymph nodes
- a diagnosis of reactive lymphadenopathy can be given due to mixed cell population observed
9
Q
How can antibody levels in patients be used diagnostically?
A
- the levels of specific antibodies circulating in patients can be detected and used to diagnose conditions
- e.g. systemic lupus erythematosus (SLE), Sjogren’s syndrome, rheumatoid arthritis
- e.g. dsDNA circulates in many diseases and causes an autoimmune response, and the degree of this response can be predicted by looking at antibody levels
10
Q
What are antibody conjugates?
A
- things we attach to the Fc region of antibodies to make them useful in diagnosis
- e.g. enzymes, fluorescent probes, magnetic beads, drugs
11
Q
How can enzymes be used as antibody conjugates?
A
- e.g. peroxidase, alkaline phosphatase
- if we bind antibody to antigen and add colourless substrate, the enzyme can turn that substrate into a coloured product wherever antibodies are bound e.g. CD31 detection in Kaposi’s sarcoma
12
Q
How can fluorescent probes be used as antibody conjugates?
A
- can allow rapid measurement of the levels of molecules within a sample
- can also do multi-plexing - use several antibodies with different fluorophores (colours) that allow us to measure several molecules in a sample
- this is important as some samples are precious and difficult to obtain, so the more information we can get from them, the better
13
Q
How can magnetic beads be used as antibody conjugates?
A
- purification of cell types - can use magnet and magnetic bead attached to antibody to separate a cell type from other ones
- e.g. anti-CD3 antibodies can be used to deplete bone marrow of T cells, before we use them in bone marrow grafts - quick process
14
Q
How can drugs be used as antibody conjugates? (example)
A
- e.g. Kadcyla - an anti-HER2 antibody linked to the cytotoxic chemical emtansine
- HER2 is overexpressed in 30% of breast cancers
- the antibody can deliver drugs directly to breast cancer cells - NICE approved treatment
15
Q
What is direct detection?
A
- where there is a conjugate attached to an antibody (primary antibody), which directly detects the antigen
