Neoplasia I Flashcards
What is a neoplasm?
This is an abnormal growth of cells which persists after the stimulus has been removed
What is a malignant neoplasm?
An abnormal growth of cells which persists after the stimulus has been removed AND invades surrounding tissue, with the ability to spread to distant sites
How does dysplasia differ to neoplasia?
Dysplasia is reversible whereas neoplasia is not. Dysplastic cells show disordered tissue organisation and are said to be pre-neoplastic
What is the difference between benign and malignant neoplasms?
Benign neoplasms are confined to a primary site. Malignant neoplasms have the ability to spread to distant sites and invade other tissues. If on a surface, malignant tumours may show irregular borders, areas of ulceration or areas of necrosis
Explain microscopic identification and grading of neoplastic tissue
A benign neoplasm has cells which closely resemble the parent tissue; they are well differentiated. Malignant neoplasms range from well to poorly differentiated.
Anaplastic cells show no resemblance to any tissue type
Pleomorphic cells show great variety in size and shape
There is increased nuclear staining (hyperchromasia)
There is increased nuclear size
Increased nuclear to cytoplasm ratio
More mitotic divisions seen
What causes neoplasia?
Neoplasia is caused by accumulated mutations in somatic cells. The mutations are caused by initiators, and cell proliferation by promoters. Together these two factors form a monoclonal cell population. Neoplasms occur from this cell population through a process of progression, characterised by the accumulation of yet more mutations.
What is a monoclonal cell population, and how do we know that neoplasms are monoclonal?
A monoclonal population is a large group of cells which originated from one cell only. We know that neoplasms are monoclonal through studies of hetero and homozygous individuals, where heterozygous individuals still only showed one cell type.
Which genes are particularly susceptible to genetic alterations?
Proto-oncogenes and tumour-suppressant genes. When proto oncogenes become abnormally activated then they are called oncogenes.
Briefly explain how neoplasms are named:
- benign vs. malignant
- above or below/ through the basement membrane
- connective tissue, plasma cells, bone marrow
- immature precursor cells, mainly in children
- benign end in ‘oma’, malignant in ‘carcinoma’
- above ‘in situ’, below ‘invasive’
- connective tissue: sarcoma, plasma: myeloma, bone marrow: leukaemia
- immature precursor: blastoma, i.e. osteoblastoma
What are the steps of a metastatic invasion?
- grow and invade at a primary site
- enter a transport system and lodge at a secondary site
- grow at the secondary site (colonisation)
What three important factors are required for neoplastic invasion?
- altered adhesion
- stromal proteolysis
- motility
These cells look more like mesenchymal cells, rather than the original epithelia. Therefore this is called epithelial-to-mesenchymal transition (EMT)
How can malignant neoplasms spread?
- blood vessels via capillaries and venules
- lymphatic systems
- fluid in body cavities i.e. peritoneal - transcoelomic
If it grows at a second site and is observed then this is called a clinical metastasis. Sometimes little bits of neoplasm break off and lodge at a distant site but fail to grow. This is called a micrometastases, leading to a phenomenon known as dormancy. These are usually responsible for apparent relapses, when the previously inactive micrometastase starts to grow.
How might a neoplasm affect the primary tissue site and its function?
- direct invasion and destruction of normal tissue
- ulceration leading to bleeding
- compression of adjacent structures
- blocking of tubes and orifices
What the difference between a neoplasm and a malignant neoplasm?
A neoplasm is an abnormal growth of cells which persist after the initial stimulus has been removed. For these cells to be classed as malignant they must have invaded surrounding tissue, with the ability to spread to distant sites.
What the difference between a neoplasm and a malignant neoplasm?
A neoplasm is an abnormal growth of cells which persist after the initial stimulus has been removed. For these cells to be classed as malignant they must have invaded surrounding tissue, with the ability to spread to distant sites.
