Investigative procedures Flashcards
what are the steps involved in preparing a specimen
- preserving - tissue is placed in a fixative such as formalin
- selecting - pieces of tissue to examine under the microscope
- embedding - the selected tissue in paraffin wax
- cutting - 5um thick section from the paraffin wax block, wax sections are then floated on a warm waterbacth and captured onto slides (mounting)
what does silver stain stain
stains basement membranes black
what is a neoplasm
a neoplasm is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of normal tissue
what is benign
tumour remains localised and is not able to spread
when Oma is added onto the end of the word what does this mean
means that the cell of origin is a benign tumour
where is fibroma from
benign tumour in fibrous tissue
where is papilloma from
a benign epithelial neoplasm that extends finger like projections outward from an epithelial surface
what does malignant mean
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
malignant tumours that rise from the epithelium are called
carcinoma
malignant timorous arise form mesenchymal tissues are called
sarcomas
what can malignant tumours do
break through the basement membrane and invade underlying tissue
what do malignant tumour show
- 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
what is immunohistochemistry
this is a widely used method that labels antibodies to detect specific antigens in tissue sections
antibodies can be …
polyclonal or monoclonal
- from one lymphocytes clone therefore to a specific site on the antigen
what are the steps involved in immunohistochemsitry
- incubation of the tissue with the antigen-specific antibody (the primary antibody)
- 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 - viewing the complex with a microscope
what are the Amin uses of immunohistochemistry
- 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
what are the antigens positive reaction indicate
- Desmin
- leukocyte common antigen
- epithelial membrane antigen
- neurofilament
- S100
- vimentin
- muscle tumour
- lymphoma
- epithelial tumour
- neural tumour
- melanocytes tumour
- mesenchymal tumour
epithelial tumours do no…
arise in the CNS
- arose somewhere else and spread to the CNS and this scaled metastasis
what is electron microscopy
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
what are the main uses of electron microscopy
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
what is cytology
the study of cells rather than tissue
what does cytology involve
- obtain a sample of cells
- fixed onto a slide
- stained and examined microscopically
how can cells be obtained in cytology…
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
what are the main uses of cytology
- diagnosis of benign or malignant tumours
- diagnosis of specific infections
- screening for malignancy in at risk populations
what are the advantages of cytology
- painless procedure
- technique is simpler and can be performed anywhere
- results can be obtained more quickly
what are the disadvantages of cytology
- tissue architecture cannot be assessed
- difficult to distinguish between in situ and invasive carcinomas
WHAT DOES HISTOLOGY show in comparison to cytology
histology shows organisation and architecture
what are the main clinical uses of molecular biology
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
what is in situ hybridisation
- used in diagnostic histopathology
- detect proteins in tissues
we use labelled RNA or DNA probes in order to detect RNA or DNA
