1. Introduction Flashcards
What is a histology?
Core biopsies - used to find actual causes or what exactly something is.
What is a cytology?
Fine needle aspirates eg of breast - used to see if it is cancer.
What does the grade of cancer refer to?
How close are the cells to normal cells?
What does the stage of cancer refer to?
Size/extent of tumour and whether or not has spread to other tissues
How can histology help in cancer surgery other than just finding the type, grade and stage of cancer?
Completeness of excision and if margins are involved which.
Likely efficacy of further treatments eg HER2 a growth factor receptor which predicts the response of breast cancer to the drug Herceptin.
How do you stop the process of autolysis (after a specimen has been taken)? What does it do?
Fixation - formalin.
Inactivated tissue enzymes, denatures proteins, prevents bacterial growth, hardens tissue.
Once fixed what happens to a specimen?
Trimming - Samples taken, size of stamp, put into cassette and into formalin.
How are specimens hardened?
Dehydrate using alcohol in vacuum, replace alcohol with xylene, replace xylene with molten paraffin wax.
After hardening, how are slices of specimen taken?
Take tissue out of cassette and put onto metal block. Fill with molten paraffin wax, place body of cassette on top. Set, remove metal block, cut into thin sections using microtome.
How are the slices of section put onto the microscope slide?
Float on water bath and picked up onto microscope slide
What stain is typically used on sections? How does it work?
H&E
Haematoxylin - nuclei purple
Eosin - cytoplasm and connective tissue pink
How is the tissue slice preserved and protected?
Mounting - mounting medium applied, and coverslip put on top
What is immunohistochemistry?
Demonstrates substances in or on cells by labelling them with specific antibodies. Usually the antibody is joined to an enzyme that catalyses a colour producing reaction.
What colour does immunohistochemistry usually highlight substances?
Brown
What could be identified in immunohistochemistry to show smooth muscle cells?
Contractile protein actin
What are cytokeratins?
Intracellular fibrous proteins present in almost all epithelia. Give information about primary site of a carcinoma.
What is molecular pathology?
Studies how diseases are caused by alterations in normal cellular molecular biology - DNA, RNA, proteins
Give an example of an in situ molecular test that shows how DNA is altered in tissues prepared for microscopy
FISH eg gains of additional copies of Her2 gene in breast cancer
What type of sequencing allows may genes to be tested simultaneously for mutations?
Next generation sequencing
What can mRNA expression profiling methods show?
How active a large number of genes are, at the RNA level - so can predict how a tumour is likely to behave
When are frozen sections used? What is it?
Intra-operative, when result determines course of operation eg if is cancer for resection, is rapid freezing of tissue on a cryostat.
What is the problem with frozen sections?
Morphology not as good, so reduced accuracy (misinterpretation leading to false negatives, and a sense of diagnostic tissue in frozen section).
