Session 8 Flashcards
What is a neoplasm?
An abnormal growth of cells that persists after the initial stimulus is removed.
What are malignant neoplasms?
Neoplasms that invade surrounding tissue with potential to spread to different sites. It can be described as cancer.
What is a tumour?
Any clinically detectable limb or swelling.
What is a metastasis?
A malignant neoplasm that has spread from it’s original site to a new non-contiguous site. The original location is the primary site and the place to which it has spread is the secondary site.
What is dysplasia and why isn’t it neoplastic?
A pre-neoplastic alteration in which cells show disorientated tissue orientation. It is not neoplastic because the change is reversible.
How to benign and malignant neoplasms appear different to the naked eye?
Benign tumours grow in a confined local area with a pushing outer margin.
Malignant tumours have a irregular outer margin and shape and may show areas of ulceration or necrosis if on a surface.
How to benign and malignant neoplasms appear different under the microscope?
Benign neoplasms are well differentiated - the cells closely resemble the parent tissue.
Malignant neoplasms range from well differentiated to poorly differentiated.
Dysplasia also represents altered differentiation.
When are cells described as anaplastic?
When they have no resemblance to any tissue (no differentiation)
What is seen in individual cells with worse in differentiation?
Increasing nuclear size and nuclear to cytoplasmic ratio
Increased nucleus staining (hyperchromasia)
More mitotic figures
Increasing variation in the size and shape of cells and nuclei (pleomorphism)
What term do clinicians use to describe differentiation?
Grade - high grade being poorly differentiated. G1-4.
How do neoplasms form?
They are caused by accumulated mutations in somatic cells. The mutations are caused by initiators, which are mutagenic agents, and promoters, which cause cell proliferation. In combination these result in an expanded, monoclonal population of mutant cells.
Chemicals, infections and radiation are the main initiators but some of these agents can also act as promoters.
Mutations can also be inherited, giving the neoplastic cells a head start.
A neoplasm emerges through a monoclonal population of cells through a process called progression, characterised by the accumulation of yet more mutations.
What is the evidence that neoplasms are monoclonal?
From the study of the X-linked gene for the enzyme G6PD in tumour tissue for women. This gene has several different isoenzymes. In early female embryogenesis one allele is randomly activated in each cell (Lyonisation). In heterozygous women that happen to have a heat stable and a heat labile isoenzyme, normal tissues will be a patchwork of each type. However neoplastic tissues only express one isoenzyme indicating a monoclonal group of cells.
What factors does the organised system of naming neoplasms take into account?
Site of origin, whether it is benign/malignant, the type of tissue the tumour forms and sometimes the gross morphology (e.g. Cyst or papilloma).
What is the suffix for benign and malignant tumours?
Benign: -oma
Malignant: -sarcoma if it is a stromal malignant neoplasm and -carcinoma if it is an epithelial malignant neoplasm (~90%)
What is the two main classifications of carcinomas?
They can be in situ (no invasion of epithelial basement membrane) or invasive (penetrated through basement membrane).
