1 Introduction to Pathology Flashcards
Identify the 5 main branches of pathology
- Medical Microbiology
- Chemical Pathology
- Haematology
- Immunology (eg allergies)
- Cellular Pathology (organ examination, autopsies)
What do haematologists do?
Haematologists provide specialised services in:
- Transfusion
- Coagulation
- Haemoglobinopathies
- Haemato-oncology
- Bone marrow transplantation
What are the two branches of cellular pathology?
- Histopathology
- Cytopathology
What is histopathology?
Histopathology involves the macroscopic and microscopic assessment of tissue samples and the provision of clinically relevant and useful reports
What is cytopathology?
Cytopathology is similar to histopathology but the specimens consist of disaggregated cells rather than tissue
Identify 3 branches of histopathology
- Neuropathology
- Forensic Pathology
- Paediatric Pathology
What is neuropathology?
Neuropathology is a branch of histopathology that is confined to brain, spinal cord, nerves and muscle
What do forensic pathologists do?
Forensic pathologists attend crime scenes and perform autopsies in cases of suspicious death
What do paediatric pathologists do?
- Examine histopathology specimens from children
- Undertake foetal, perinatal and paediatric autopsies
Why is the examination of tissue microscopically important?
- Needed to ensure whether surgery is required
- Needed to guide the type and extent of surgery
- Gives indication about treatment options e.g radiotherapy, chemotherapy, antibiotics, steroids
Histology and cytology are both used to make microscopic diagnoses.
Distinguish between them
- Histology involves viewing microscopic slides prepared from tissue sections
- Cytology studies cells scraped from / sucked out of an organ, lesion or bodily fluid
List 4 advantages of cytology
- Non-invasive or minimally invasive
- Fast
- Cheap
- Safe
What is the main disadvantage of cytology?
Higher inadequacies and error rates than histology
Identify two uses of cytology
- Used as a preliminary test before other investigations are conducted or before histology is taken
- Used to confirm/exclude cancer or dysplasia rather than to diagnose other conditions with accuracy
Identify 4 advantages of histology
- Assesses cell architecture and cellular atypia
- Differentiates between in situ and invasive malignancy
- Determines completeness of excision
- Allows for grading and staging
What sort of testing is better for histology than cytology?
Histological sections are better for immunohistochemical and molecular testing than cytological preparations
What does immunohistochemistry involve?
Immunohistochemistry demonstrates the presence in or on cells of specific substances, usually proteins, by labelling them with antibodies
Outline immunohistochemistry testing
- Antibodies are joined to an enzyme that catalyses a colour-producing reaction
- Antigenic substances are commonly demonstrated by the presence of a brown colour.
Identify 5 antigenic substances which can be detected in immunohistochemistry testing
- Actin
- Cytokeratins
- Microorganisms e.g. HPV, herpes simplex
- Hormone receptors e.g. oestrogen receptor (ER) - Her2 receptor
What is the Her2 receptor?
Her2 receptor is a growth factor receptor which predicts the response of breast cancer to the drug Herceptin (see neoplasia)
What are cytokeratins?
Cytokeratins are fibrous proteins which are present in almost all epithelia
What is the value of detecting cytokeratins?
- Their presence demonstrates epithelial differentiation and they show tissue-specific distribution
- They can be used to give information about the primary site of a carcinoma
What is molecular pathology?
- Molecular pathology is the study of how diseases are caused by alterations in normal cellular molecular biology
- This can be due to altered DNA, RNA or proteins
Identify the steps involved in drawing up a histology report
- Fixation
- Trimming
- Embedding
- Blocking
- Microtomy
- Staining
- Mounting
- Microscopy
- Report writing
Mnemonic: Free The Eagles Because My School Makes Me Realise
What are frozen sections?
- Frozen sections are histological preparations that involve rapidly freezing a small piece of fresh tissue on a cryostat
- Used under time restraints (duration = 10 mins)
- Tissue can then be sliced, stained, mounted and passed to a pathologist for microscopy
Provide and example situation of when frozen sections are used
Tissue for frozen section is taken during the course of an operation with the aim of establishing the presence and nature of a lesion whilst the patient is still under anaesthetic
Define disease
Pathological condition- characterised by identifiable group of symtoms
Outline the differences between Histology and Cytology
SAMPLES:
Histology= Core biopsies, cancer resection specimens
Cytology= fine needle aspirates eg breast, sputum, urine
Cytology=faster and cheaper BUT less accurate/definitive
Histology= provides more info, better for molecular testing, can differetiate between invasive and in situ disease
Name and explain some potential problems faced by histopathologists
- Autolysis (self digestion)- blocked by fixation-formalin
- Choosing right bit of tissue
- Getting tissue into right format to be examined
- Cutting thin sections using microtome
- H&E staining
- Nuclei=purple
- Cytoplasm=pink
Why might they sequence some DNA which has been purified from a tumour in the lab?
Show if mutation=present in particular gene-determine treatment
What does mRNA profiling show?
Level of activity of large number of genes simultaneously
