Histopathology Flashcards
Define the following terms:
Histopathologist
Cytopathologist
Histopathologist - deals w tissues. They will examine sections, noting the architecture of the tissue and asking what it tells us about a particular condition - diagnosis + efficacy of a treatment.
Cytopathologist - deals w cells. The individuals responsible for taking cells from the patient, preparing them for examination and then delivering their diagnosis on the cell sample.
What types of tissue samples do histopathologists work with?
Biopsies
Resection specimens
Frozen sections
Post-Mortems
What are biopsies? How are biopsies preserved?
Why are biopsies embedded in paraffin wax?
Biopsies = small sections of tissues that are removed from the patient and typically placed in formalin solution which preserves the tissues by cross linking proteins.
Biopsies are embedded in paraffin wax to allow very thin sections to be cut by a microtome. These are mounted on a glass microscope slide for further prep prior to analysis.
What questions can microscopic examination of a biopsy answer? (3)
What is the Haemotoxylin and eosin (H&E) stain used for, when examining biopsies?
What is the Ziehl neelsen stain used to identify?
Why do biopsies need to be correctly labelled?
- Is the tissue normal?
- Is the tissue inflamed and if it is, what’s the likely cause?
- Is the tissue cancerous and, if it is, what type of cancer is it?
H&E stain - identifies nuclei and cytoplasmic granules of leukocytes within tissues
Ziehl-neelsen stain - stains acid fast bacteria red -> helps diagnosis TB.
Biopsies need to be correctly labelled to avoid confusion / misdiagnosis.
What are resection specimens?
What are resections primarily used to look at?
Resection specimens = sections taken from tissue that has been removed as part of a surgical procedure and can be processed as for a biopsy.
Resection specimens are used to look at the stage the disease has progressed to.
What are frozen sections?
How is the tissue section frozen?
What is the main benefit of a frozen section?
Not all processes are compatible w initial preparation of the sample, what do tissues for frozen sections need to be?
Frozen sections - taken during surgical procedures and are examined by pathologists in real time while the patient is being operated upon.
The freshly taken tissue is frozen by a cryostat, cut then mounted on glass slides and stained for biopsies.
Frozen section procedure can give a rapid diagnosis in mins to be relayed back to the surgeon to inform the surgery.
Tissue for frozen sections needs to be fresh and free of preservatives like formalin.
How long do each of the following take for results to be sent to clinicians from the histopathology lab?
Frozen section: 30 mins
Biopsies: 2-3 days
Resection specimens: 5-7 days
Cytopathology:
What is the fine needle aspiration technique useful for?
What is a downside of using fine needle aspiration?
Fine need can be used to get into a lesion and suck out (aspirate) the cells which can be analysed.
The needle can penetrate relatively inaccessible tissues without the need for surgery.
Downside of this technique: cytopathologist is only looking at cells and unable to comment upon the likely architecture of the tissue.
Histopathology and cytopathology are a powerful combination, what can immunohistochemistry be used to identify?
What is kaposi’s sarcoma?
Immunohistochem can be used to identify key molecules within the tissues.
Karposi’s sarcoma = rare cancer, indicative of immunodeficiency
What are examples of antibody conjugates?
How can antibodies be used as diagnostic tools?
Conjugations:
- enzymes e.g. peroxidase
- fluorescent probes - these can allow the rapid measurement of levels of molecules within a sample
- magnetic bead - e.g the purification of cell types
- drugs
Antibodies can be used to directly and indirectly detect antigens.
What are manufactured antibodies used for?
- blood group serology
- immunoassays e.g. detection of hormones circulating antibodies/antigens
- immunodiagnosis e.g. infectious diseases, antibody levels, IgE
How does an ELISA (enzyme linked immunosorbent assay) test work?
- clinical samples (e.g adheres to a plastic plate)
- probe w specific antibody raised against the molecule of interest
- enzyme conjugation generates a coloured product
- reference to a standard curve to determine precise concs of the molecule in the sample
How does flow cytometry work?
What info does it give you about the cells?
Cells are labelled w differently conjugated Abs
Run as a stream of single cells through a laser beam
Colour of light emitted and the forward or side scatter of the laser beam denotes the identity of the cell surface molecules expressed and the size and granularity of the cells.
Anti CD3+ = T cells - pan T cell marker Anti CD4+ = T cells - t helper cells Anti CD8+ = cytotoxic T cells Anti CD19+ = B cells Anti CD56+ = natural killer (NK) cells
