Histopathology Flashcards
(29 cards)
What is a histopathologist
deals with tissues. She/he will examine sections, noting the architecture of the tissue and asking what it tells us about a particular condition.
What is a cytopathologist
deals with cells. They are often are the individuals responsible for taking the cells from the patient, preparing them for examination and then delivering their expert diagnosis on the cell sample.
What 4 samples do histopathologist deal with
Biopsies, Resection specimens, frozen sections and post-mortems
How are biopsies formed
1) Tissue removed from patient is placed in formalin solution which preserves tissues by cross-linking proteins
2) Then embedded in paraffin wax to allow very thin sections (2-3um)
3) cut by an instrument known as a microtome
4) Mounted on a glass microscope slide for further preparation prior to analysis
What questions can biopsies answer
- Is tissue normal?
- Is the tissue inflamed and what is the likely cause?
- Is the tissue cancerous and what type is it?
- Biopsies are primarily used to make diagnoses e.g. is there a need for surgery?
What do Haemotoxylin and Eosin do?
Identify the nuclei and cytoplasmic granules of leukocytes
What do Zieh-Neelsen stain do?
Stain acid-fast bacteria red which aids the diagnosis of tubercolosis .
*Acid-fast bacteria (also known as acid-fast bacilli or AFB) are microorganisms resistant to decolorization by an acid, hence, the term acid-fast. Acid fastness is a unique characteristic of M. tuberculosis
What does Oil Red O stain do?
stains lipids
what does congo red do?
stains collagen and elastin (ECM components)
How are resections occupied?
Taken from tissue that has been removed as part of a surgical procedure and can be processed as for a biopsy.
What are resections used to look at?
Primarily look at the stage of the disease, eg.
How far is the cancer progressing?
Has the cancer penetrated the bowel wall, spread to the lymph nodes or liver?
Has all the cancerous tissue been removed or is chemo needed?
Frozen sections
Taken during surgical procedures and are examined by pathologists in real time while the patient is being operated upon.
The procedure can give a rapid diagnosis in minutes which can be relayed back to the surgeon to inform the surgery.
Hoe is a frozen section obtained?
The freshly taken tissue is frozen by a machine known as a cryostat
Cut
Then mounted on glass slides and stained as for biopsies.
Tissues need to be fresh and free of preservatives like formalin
Questions that can be answered with a frozen section
Is the tissue cancerous?
Has all the cancerous tissue been removed?
Is there another pathological process going on?
Timescales of biopsies, resections and frozen sections
Frozen section: 30 mins
Biopsies:2-3 days
Resection specimen: 5-7 days
How are fine needle aspirates obtained?
a fine needle is used to get into lesion and suck out (aspirate) the cells which can then be analysed as smear.
Powerful technique as the needle can access relatively inaccessible tissues such as thyroid nodule and assess the suspect mass without need for surgery
Disadvantage of fine needle aspirates
the cytopathologist is only looking at cells and is unable to comment upon the likely architecture of the tissue.
What is immunohistochemistry?
It involves the process of selectively identifying antigens (proteins) in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues.
What can high levels of circulating antibodies recognising double stranded DNA indicate?
systemic lupus erythematosus (SLE)
Sjögren’s syndrome
Rheumatoid arthritis.
Degree of number of antibodies there can be used to indicate the number/levels of antibodies circulating in blood plasma
what can attachments include
enzymes
fluorescent probes
magnetic beads
drugs
how do enzymes attached to antibodies work
e.g. peroxidase, alkaline phosphatase. Used with a colourless substrate to give a coloured product. Also detection of oestrogen receptors on breast cancer tissue biopsies.
how do fluorescent probes attached to enzymes work
These can allow the rapid measurement of the levels of molecules within a sample. Multiplexing (using several antibodies with different fluorescence) can allow the measurement of several molecules in a single precious clinical sample.
how do magnetic beads attached to antibodies work
These can allow the rapid measurement of the levels of molecules within a sample. Multiplexing (using several antibodies with different fluorescence) can allow the measurement of several molecules in a single precious clinical sample.
how do drugs attached to antibodies work
e.g. the biological Kadcyla, an anti-HER2 antibody linked to the cytotoxic chemical emtansine.
HER2 is overexpressed in around 30% of breast cancers and Kadcyla has NICE (National Institute for Health and Care Excellence) approval for the treatment of advanced metastatic breast cancers.
