abnormal cell growth Flashcards
what is agenesis?
complete absence of an organ primordium like a kidney, absence of part of an organ or absence of the cells within an organ
what is aplasia?
absence of an organ coupled with the persistence of an organ anlage or a rudiment that never developed such as a lung where the bronchus ends blindly
what is hypoplasia? give an example and what this is
reduced size owing to the incomplete development of all or part of an organ e.g. microphlamia which is where the eyes are small
what is dysgraphics? Give an example of what it ius
defects caused by the failiure of apposed structures to fuse e.g. spina bifida which is incpmplete closure of the neural tube causing the spinal cord to remain exposed
what is atrophy? what can it occur as a result of? give an example of a physical atrophy
-shrinkage in size of cells by loss of cell substance causing loss of tissue or reduced cell division
-decreased workload, diminshed blood supply, loss of innervation and inadequate nutrition e.g. when a broken leg is in a cast and doesnt get used
-decreased synthesis/ increased metabolism
-ovary post menopause
what is hypertrophy, what does it often occur with?
-an increrase in the size of cells and hence increase in the size of an organ for example the uterus in pregnancy undergoes hypertrophy
-hyperplasia
what is hyperplasia? what causes it? give an example of hyperplasia
the increase in the number of cells in an organ or tissue
-hormonal stimulation
-increased functi0onal demand like chronic inflammation
-persistent cell injury
-example is breast epithelium in pregnancy or while lactating
what is metaplasia? how might it occur? what might it lead to? what is the most common type?
the conversion of one differentiated cell type to another
-replacement of glandular epithelium with squamous
-response to persistent injury
-may lead to neoplastic transformation in dysplasia
-most common type is squamous metaplasia
what is dysplasia? what is it associated with? what could it lead to the development of?
an alteration in the size, shape and organization of the cellular components of a tissue in the superbasal layers and is often subsequent to metaplasia
-commonly associated with squamous epithelium
-usually the lesion that is present before a carcinoma develops
how is a carcinoma in situ differnet to a carcinoma that is invasive?
it still has an intact basal membrane
what are the characteristics of a carcinoma in situ?
-thick, disorderly arrangement of cells
-mitoses above the basal layer
-individual cells form keratin beneath the surface
-pleomorphism
-increased nuclear-cytoplasmic ratio
what are the stages in the development of invasive cervical cancer?
- start as normal columnar epithelium and normal squamous epithelium
- metaplastic squamous epithelium
- dysplastic squamous epithelium
- carcinoma in situ
- invasion through underlying basement membrane
- metastases
- establishes new growth at new site
when does a carcinoma become invasive?
once it’s broken through the basement membrane
what are the stages of development of an invasive carcinoma?
- invasion of the basement membrane through binding and degradation
- this is by expressing surface adhesion molecules where tumour cell adehsion molecules bind to the underlying extracellular matrix
- tumour cells disrupt and invade the extracellular matrix
- tumour cells metastasize by way of blood vessels or lymphatics
- they then exit from circulation by adhering to the epithelial cells and emigrating through the blood vessel to form a secondary deposit
- angiogenesis is needed for survival and growth of the tumour so growth factors are secreted
- a new blood supply is established for the growing tissue
what is the scientific term of a cancer?
neoplasm
what are the different types of cancers?
-carcinomas (most common) and are epithelial
-sarcomas which occur in connective tissue, muscle and bone
-leukemias and lymphomas occur in circulatory or lymphatic systems
-blastoma occurs in precoursor stem cells ( in foetus)
-teratoma which may contain immature or fully formed tissue not normally present at the site
what are the classifications of cancer by cell type
-adenomatous which are carcinomas derived from ductal or glandular cells
-squamous - derived from squamous epithelial cells
-myeloid derived from blood cells
-lymphoid derived from lymphocytes
when are benign tumours dangerous?
depends on their position such as a benign tumour putting pressure on the brain
What’s the difference between malignant tumours and benign tumours?
Malignant tumours grow rapidly, are less compact and are more likely to be life threatening while benign tumours are more slow growing, more compact and are less likely to be life threatening
how do benign and malignant tumours compare in the following areas:
-growth rate
-cells
-resemble parent tissue
-infiltrating
-spread to distant sites
-ability to kill
-benign are slow whereas malignant are fast
-benign: normal malignant: abnormal
-benign: yes malignant no
-benign no malignant yes
-benign no malignant yes
-benign only if vital function is damaged, malignant yes always if left untreated
how is a tumour initiated?
when there us a loss of tumour supressor gene function which allows the abnormal expression of oncogenes to undergo neoplastic transformation causing the oncogenes to be expressed
what percentage of cancers are inherited?
5-10%
what are the cancer gene identified
-p53 gene
-rb which is the familial retinoblastoma gene
give some environmental cancer risk factors
-viruses
-tobacco
-food
-chemicals
-pollution
give some genetic factors for cancer
sex
age
race
what percentage of uk deaths are due to cancer
28%
what percentage of cancer deaths in the uk are women and what percent are men
47% women and 53% men
how much is the economic and healthcare cost of cancer in the UK
15.8 billion per annum
give two benign occular tumours
-choroidal nevi
-iris nevi
give two malignant ocular tumours
-melanoma
-retinoblastoma
whats the most common priamry intaoccular malignancy?
melanoma
Give some statistics on melanoma
-affects 7-800 cases per year in the uk
-most common in ages 55-65 years
-99% of cases are in white people
-80% of cases the melanoma is in the choroid
what cells do occular melanoma arise from
melanocytes
what does a malignant choroidal melanoma look like?
a dark mass beneath the blood vessels in the retina
what is a retinoblastoma?
rare childhood cancer but is the most common intraocular neoplasm in childeren up to 2 years old
what causes retinoblastoma?
mutations in the rb tumour suppressor gene
what percent of retinoblastoma cases are inherited?
25-30% via autosomal dominant inheritance
what is the two hit hypothesis in the Rb gene
where both of the alleles have to be affected for the Rb to develop
how does inherited retinoblastoma develop?
- inherited absence of one of the paired Rb1 genes at birth
- mutational loss of Rb1 gene in any retinal cell
- there’s a high risk of bilateral retinoblastoma
how does sporadic Rb develop?
- normally paried Rb1 genes at birth
- a mutational loss of one Rb1 gene occurs
- a mutational loss of the other Rb1 gene in the same cell or its daughter cell occurs
which stage of cervical cancer development is characterised by a pre-neoplastic lesion?
dysplasia
What is required for a newly established tumour to grow greater than 0.05mm? How is this triggered?
new blood supply
triggered by:
-tumour cells, growth factors
-angiogenesis
In which genes do mutations occur that result in abnormal cell growth?
proto-oncogenes
tumour suppressor genes
