Lecture 20 - Neoplasia Review Flashcards
What is a tumour?
A swelling (can be from inflammation)
Any clinically detectable lump or swelling
What is a neoplasm?
An abnormal growth of cells that persists after the initial stimulus is removed
Has autonomous growth
What is a benign neoplasm?
Gross and microscopic appearances are considered to be innocent, implying that it will remain localised and will not spread to other sites
What is Cancer?
A malignant neoplasm
What is a malignant neoplasm?
An abnormal growth of cells that persists after the initial stimulus is removed and invades surrounding tissue with the potential to spread to distant sites
What is a metastasis?
Malignant neoplasm that has spread from its original site to a new non-contiguous site
What is dysplasia?
Pre-neoplastic alteration in which the cells show disordered tissue organisation (altered differentiation)
HAVE NOT YET BREACHED THE BASEMENT MEMBRANE
Is dysplasia reversible?
Yes
How may cells in dysplasia look?
Pleomorphic
Large hyperchromatic nuclei
High nuclear to cytoplasmic ratio
What infection can result in dysplasia in cervical epithelium?
Human Papilloma Virus
HPV
How does the dysplasia progress in the cervical epithelium upon infection by HPV?
Mild dysplasia (CIN1) affects lower 1/3 of epithelium
Moderate dysplasia (CIN2) affects lower 2/3s of epithelium
Full thickness dysplasia (CIN3) affects all of epithelium, also know as carcinoma in situ
Once the atypical cells breach the basement membrane this becomes invasive squamous cell carcinoma
What is the purpose of the cervical screening programme?
Detect dysplasia at an early stage and treat it before it progresses to cancer
Prevent morbidity and mortality from cancer and treatment
What stage of dysplasia is irreversible (no longer reversible back to normal)?
CIN III when its carcinoma in situ or invasive carcinoma
How do benign neoplasms and malignant neoplasms differ in their growth behaviour?
Benign = expansive growth locally with a pushing outer margin
Malignant = expansive and invasive with an infiltrating pattern
How do benign neoplasms and malignant neoplasms differ in their location?
Benign = remain confined to site of origin, don’t produce metastases
Malignant = can metastasis
How do benign neoplasms and malignant neoplasms differ in their function?
Benign = retains function of its cells of origin
Malignant = less likely to retain functions of cells of origin
How do benign neoplasms and malignant neoplasms differ in their histology?
Benign:
-resembles cells of origin
-few mitoses
-normal/mild increase in nuclear : cytoplasmic ratio
-cells uniform
Malignant:
-failure to full differentiate
-many mitoses
-high nuclear : cytoplasmic ratio
-pleomorphism (cells/nuclei vary in size and shape)
What is differentiation?
Process of becoming different by growth or development
What is meant be anaplastic?
Cells have differentiated with no resemblance to any tissue
What are the cytological features of malignancy?
-increasing nuclear size
-increased nuclear:cytoplasmic size
-increased nuclear staining (hyperchromasia)
-increased mitotic figures
-varied size and shape of cells and nuclei (pleomorphism)
As grade of degree of differentiation gets higher, how does the differentiation change?
Higher the grade means the more poorly differentiated
The more likely the outcome will be negative
Why/how does neoplasia occur?
Accumulation of NON-LETHAL mutations in somatic cells
What are some inherited germiline mutations causing neoplasia?
BRCA1
BRCA2
What are initiators?
Mutagenic agents that cause the mutations leading to neoplasia
What are promoters?
Something that results in cell proliferation of a neoplastic clone
What are some common examples of chemical initiators?
Smoking
Alcohol
Diet
Obesity
What is a common infectious agent causing neoplasia?
HPV
What type of cancer does the chemical 2-napthylamine lead to?
Bladder cancer
What type of cancer does UV light often cause?
Malignant melanoma
Briefly describe how a neoplasm develops:
Initiator is supplied to cells
Long periods of promotion (clonal expansion) increases size of neoplastic population
Produces monoclonal population
What are some genes that can be mutated give a “head start/first hit”?
BRCA1/BRCA2
What is progression?
The stepwise accumulation of complimentary mutations the occur over time that provide the cancer cells with a survival advantage
What is the Adenoma-Carcinoma sequence?
What is this process very common for?
The pattern of accumulation of mutations in a certain sequence that happens over time
Wnt pathway activated —> EGFR signalling activated —> TGFB response inactivated —> loss of p53 function
Corresponds to
Early adenoma —> intermediate adenoma —> late adenoma —> carcinoma —> metastasis
Very common in sporadic Colon cancer
What are the 4 classes of normal regulatory genes?
-growth promoting Proto-oncogenes
-growth inhibiting Tumour suppressor genes
-Genes regulating apoptosis
-Genes involved in DNA repair
What is the function of proto-oncogenes?
Drive cell proliferation
What do Proto-oncogenes become when they mutate?
What do these mutated versions do?
Oncogenes
Oncogenes create oncoproteins which promote cell growth in the absence of normal growth promoting signals
How many proto-oncogenes need to be mutated in order for oncogenesis to occur?
1 proto-oncogene mutated since oncogenes are dominant over proto-oncogenes
What is the most common proto—oncogene mutated in a human tumour?
(kRAS)
What type of cancer is RAS mutation very prominent?
Pancreatic adenocarcinoma
What happens when the RAS gene is mutated so its permanently activated?
RAS Phosphorylates Retinoblastoma gene permanently activating it
This allows the cell to constantly progress through the cell cycle
What is the function of a tumour suppressor gene?
Causes loss of function
How many tumour suppressor genes need to be mutated for oncogenesis to occur and why?
Both alleles must be damaged
Mutated tumour suppressor gene is recessive compared to healthy tumour suppressor gene
What is the 2 hit hypothesis?
The need to have both alleles of tumour suppressor genes mutated/inactivated
What is the function of the retinoblastoma gene?
What happens when the Retinoblastoma gene is inhibited?
A key negative regulator G1/S cell cycle checkpoint
Gene allows cells to progress through the cell cycle into phase allowing for continued proliferation
What happens when p53 is disrupted?
What type of gene is this?
Impaired apoptosis
Tumour suppressor gene
What are 3 types of DNA repair whose genes can be mutated?
Mismatch repair
Nucleotide excision
Double strand breaks