Neoplasia Flashcards
What is neoplasia
Increas in the number of cells in a tissue - growth exceeds and is uncoordinated with normal tissues
Persists in an excessive manner after cessation of the stimuli that evoked the change
In hyperplasia - growth attains equilibrium - in neoplasia it does not
What does neoplasia result from
Upregulation or proliferation (oncogene) or failure of apoptosis mechanism (TSGs)
What is carcinogenesis
Non-lethal genetic damage that contributes to cell undergoing neoplasia
E.g. DNA deletion, mutation, amplification, translocation or insertion which leads to loss/gain of function
What are chemical carcinogens
Initiation - short exposure with mutations
Promotion - long term exposure which encourages cellular proliferation and is not usually mutagenic
Initiate and promote = complete carcinogens
What happens in microbial carcinogenesis
Oncogenic viruses sucha s HPV 16,18 can cause papillomas
HPV 11 can cause lacrimal paiplloma
EBV causes bUrkitt’s lymphoma and intraocular large B cell lymphoma
What is physical carcinogenesis?
Ionizing radiation and UV radiation directly damages DNA and can result in a range of changes form single gene mutations to major chromosome deletions
UV mainly affects skin forming pyramidine dimers that are usually excised by DNA repair mechanisms
What are proto-oncogenes?
Code for proteins involved in cell proliferation including growth factors, receptors, signal transducers, nuclear regulating proteins
In neoplasia - become oncogenes through structural change, chromosomal translocation or amplification
What are tumour suppressor genes?
Switch off cell prolferation
Loss of both copies of a TSG is required for neoplasia to develop - two hit hypothesis
What are mechanisms of oncogene production
Structural change - single point mutation in ras gene leads to inability of protein to hydrolyse GTP - signalling permanently switched on
Translocation - Burkitt’s lymphoma - myc proto-oncogene is translocated from 8 to 24 leading to permanent expression
CML abl from 9 to 22 philly chromosome
Amplication - overexpression of DNA segments
Where is p53 genel located? What does it do?
chomosome 17 p 13.1
Cell cycle arrest and initiation of apoptosis
How can defects in DNA repair occur?
Mismatch repair
Nucleotide excision repair
Recombination repair
What are hamartomas
Non-neoplastic malformation that consists of a mixture of tissue normally found at a particular site
e.g. haemangiomas, naevi
What is a haemangioma
Proliferation of vascular channels with a lobulated growth pattern
What are naevi
MElanocytes that migrate through the dermis to reach epithelial cells
Abnormal migration, proliferation, maturation
What is a chorisoma?
Non-neoplastic malformation consisting of a mixture of tissues not normally present
E.g. epibulbar dermoids - smooth white nodule with or without hair on the bulbar conjunctiva - fibrous tissue, fat, hair, sweat glands
Phakomatous choristoma - nodule int eh eyelid - lens capsule epithelial and basement membrane cells
