Investigative procedures

Question 1

what are the steps involved in preparing a specimen

Answer 1

1. preserving - tissue is placed in a fixative such as formalin
2. selecting - pieces of tissue to examine under the microscope
3. embedding - the selected tissue in paraffin wax
4. cutting - 5um thick section from the paraffin wax block, wax sections are then floated on a warm waterbacth and captured onto slides (mounting)

Question 2

what does silver stain stain

Answer 2

stains basement membranes black

Question 3

what is a neoplasm

Answer 3

a neoplasm is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of normal tissue

Question 4

what is benign

Answer 4

tumour remains localised and is not able to spread

Question 5

when Oma is added onto the end of the word what does this mean

Answer 5

means that the cell of origin is a benign tumour

Question 6

where is fibroma from

Answer 6

benign tumour in fibrous tissue

Question 7

where is papilloma from

Answer 7

a benign epithelial neoplasm that extends finger like projections outward from an epithelial surface

Question 8

what does malignant mean

Answer 8

the term malignant when applied to a tumour suggests that a neoplasm can invade and destroy adjacent structures and metastasise (spread to distant sites) causing death

Question 9

malignant tumours that rise from the epithelium are called

Answer 9

carcinoma

Question 10

malignant timorous arise form mesenchymal tissues are called

Answer 10

sarcomas

Question 11

what can malignant tumours do

Answer 11

break through the basement membrane and invade underlying tissue

Question 12

what do malignant tumour show

Answer 12

• variable degrees of differentiation - lack of differentiation is called anaplasia and is a hallmark of malignancy,
• cellular pleomorphism - cells vary in size and shape
• abnormal nuclear morphology - such as abundant dark staining chromatin, disproportionate size for the cell such as a high nuclear to cytoplasm ration, nuclear pleomorphism, large nucleoli
• loss of polarity - sheets of cells grow in an disorganised fashion
• mitoses

many of these are typical of dysplasia which is disordered growth
- loss of uniformity of individual cells often occurs in premalignant tissues but does not always progress to malignancy

Question 13

what is immunohistochemistry

Answer 13

this is a widely used method that labels antibodies to detect specific antigens in tissue sections

Question 14

antibodies can be …

Answer 14

polyclonal or monoclonal

- from one lymphocytes clone therefore to a specific site on the antigen

Question 15

what are the steps involved in immunohistochemsitry

Answer 15

1. incubation of the tissue with the antigen-specific antibody (the primary antibody)
2. localisation of the primary antibody by using another antibody that is labelled to allow visualisation of the complex
   - labels include fluorescent compounds or enzymes that are used to precipitate a coloured product, this secondary antibody is raised agains the IgG of the species in which the primary antibody was made
3. viewing the complex with a microscope

Question 16

what are the Amin uses of immunohistochemistry

Answer 16

• tumour pathology - to demonstrate histogenesis in undifferentiated tumours by looking for antigens related to differentiation
• renal pathology - to demonstrate different types of immune complexes in glomeruli, important in the diagnosis of glomerulonephritis
• suspected infective disease - to detect specific organisms

Question 17

what are the antigens positive reaction indicate

• Desmin
• leukocyte common antigen
• epithelial membrane antigen
• neurofilament
• S100
• vimentin

Answer 17

• muscle tumour
• lymphoma
• epithelial tumour
• neural tumour
• melanocytes tumour
• mesenchymal tumour

Question 18

epithelial tumours do no…

Answer 18

arise in the CNS

- arose somewhere else and spread to the CNS and this scaled metastasis

Question 19

what is electron microscopy

Answer 19

this is when a beam of electrons is passed through ultrathin tissue sections and the images are focused by a column of electromagnetic lenses

• used of electrons allow much higher magnifications and better resolution than that obtained by light microscope
• despite this electron microscopy is not used very often and it has be superseded by immunohistochemistry which is cheaper and easier to perform and has similar use

Question 20

what are the main uses of electron microscopy

Answer 20

tumour pathology - when immunohistochemsitry has failed to provide a diagnosis in an undifferentiated tumour, ultrastructural features related to the differentiation can be sought

• renal pathology - to demonstrate the distribution of immune complexes in the glomeruli, important in the diagnosis of glomerulonephritis
• identification of viruses, amyloid and inorganic materials such as asbestos

Question 21

what is cytology

Answer 21

the study of cells rather than tissue

Question 22

what does cytology involve

Answer 22

• obtain a sample of cells
• fixed onto a slide
• stained and examined microscopically

Question 23

how can cells be obtained in cytology…

Answer 23

exfoliation - cells are shed or scraped from a mucosal surface

• sputum
• fluids
• brushings
• cervical smears

fine needle aspiration

• cells are sucked from a lump or lesion through a fine gauge needle
• breast lumps
• thyroid lumps

Question 24

what are the main uses of cytology

Answer 24

• diagnosis of benign or malignant tumours
• diagnosis of specific infections
• screening for malignancy in at risk populations

Question 25

what are the advantages of cytology

Answer 25

• painless procedure
• technique is simpler and can be performed anywhere
• results can be obtained more quickly

Question 26

what are the disadvantages of cytology

Answer 26

• tissue architecture cannot be assessed

- difficult to distinguish between in situ and invasive carcinomas

Question 27

WHAT DOES HISTOLOGY show in comparison to cytology

Answer 27

histology shows organisation and architecture

Question 28

what are the main clinical uses of molecular biology

Answer 28

detection of infectious agents 
diagnosis and prognosis of malignancy 
- gene rearrangements 
- gene translocation 
- mutated oncogenes 
- gene amplification 
- detection of a relapse 
- definition of prognostic group 
detection of hereditary disease
forensive medicine - genetics fingerprinting

Question 29

what is in situ hybridisation

Answer 29

• used in diagnostic histopathology
• detect proteins in tissues
  we use labelled RNA or DNA probes in order to detect RNA or DNA