histopathology

Question 1

• What is a histopathologist?

Answer 1

Deals with tissues
examine sections noting the architecture of the tissue
to see what it tells us about a particular condition

Question 2

• What sorts of tissue samples does a histopathologist work with?

Answer 2

Biopsies

Resection specimens 

Frozen sections 

Post-mortems

Question 3

• How do you preserve and prepare a biopsy for analysis?

Answer 3

Immersed in a formalin solutions which preserves the tissues by cross-linking proteins

Samples are embedded in paraffin wax, enabling thin sections (2-3um thick) to be cut by a microtome

Sample mounted on microscope slide for preparation prior to analysis

Question 4

• What is a resection specimen?

- What is the purpose of resections?

Answer 4

Specimens from tissue that has been removed as a part of surgical procedure and can be processed as for a biopsy

To look at the stage of the disease

e.g - stage of cancer

Question 5

• What order do the samples come in to the histopathology lab?

Answer 5

Frozen sections → Biopsies → Resection specimens

Question 6

• What questions can a microscopic examination of a biopsy answer?

Answer 6

• Is the tissue normal?
  
  • Is the tissue inflamed and, if it is, what is the likely cause?
  • Is the tissue cancerous and, if it is, what type of cancer is it?

Question 7

• What stain can be used to identify the nuclei and cytoplasmic granules of leukocytes within tissues?

Answer 7

Haemotoxylin and Eosin (H&E)

Question 8

• What stain aids in the diagnosis of TB infection by staining acid fast bacteria red?

Answer 8

Ziehl-Neeslen stain

Question 9

• What is a frozen section?

Answer 9

Taken during procedures, examined by pathologists in real time whilst the patient is being operated on

Establishes presence and quantity of cancerous tissue, as well as identifying other pathological processes

Question 10

• How are frozen sections prepared?

Answer 10

Tissue must be fresh and free of preservatives such as formalin

Tissue frozen in a cryostat (freezes freshly taken tissue),  cut, then mounted on glass slides

Then stained for biopsies

Question 11

• How long do frozen sections, biopsies and resection specimens take respectively?

Answer 11

Frozen section: 30 minutes

Biopsies: 2-3 days

Resection specimens: 5-7 days

Question 12

• What is a cytopathologist?
• What is one benefit of using fine needle aspirates?
• Give a downside to using fine needle aspirates?

Answer 12

People who work with cells which are collected and smeared onto a microscope slide

Can penetrate relatively inaccessible tissues (thyroid nodule) and so can assess the suspect mass without surgical requirement

Cytopathologist is only looking at cells and is unable to comment upon the likely architecture of the tissue

Question 13

• What is Kaposi’s sarcoma?
• What type of science can be adopted to identify specific molecules within the tissues?
• What colour and diagnosis does a positive immunohistochemical test for CD31 show?

Answer 13

Rare cancer and is often indicative of immunodeficiency (AIDS)
Spindly resembling cells evidently penetrates the collagen fibres

Immunohistochemistry

brown, endothelial cell tumour

Question 14

• What forms can antibody conjugations (attachments to the Fc region) come in?

Answer 14

Enzymes: e.g. peroxidase and alkaline phosphatase, used with a colourless substrate to produce a coloured product

Fluorescent probes: allow rapid measurement of levels of molecules within sample

Magnetic beads: purification of cell types, cells can be depleted of containments with use of a magnet eg deplete T cells before bone marrow graft

Drugs: e.g. Biological Kadcyla, an anti-HER2 antibody linked to cytotoxic chemical emtansine- against breast cancer

Question 15

• What 2 types of detection can antibodies be used for?

Answer 15

Direct - antibody with marker binds to antigen

Indirect - antibody with marker binds to primary antibody which is bound to antigen

Question 16

• Explain the steps involved in the ELISA test

Answer 16

Add Anti-A Antibody with a covalently linked enzyme to a sample with antigens bound to the surface

Wash away any unbound antibody

When colourless substrate is added, enzyme reacts with it to change the solution's colour

Measure absorbance of light by coloured product and find relative absorbance to curve

Question 17

• What is flow cytometry?

Answer 17

Flow cytometry allows the detection of specific cells (lymphocyte subpopulations) ,

using fluorescently conjugated specific antibodies that associate to the CD specific receptor sites on the lymphocyte cell surface membrane

Question 18

• Why is flow cytometry used?

Answer 18

Informative to the nature of particular inflammatory reaction

Question 19

how does flow cytometry work?

Answer 19

cells labelled with differently conjugated antibodies
run a single stream of cells through a laser beam
colour of light emitted and the forwards/ side scatter of the laser beam denotes the identity of the cell surface molecules and the size and granularity of the cells