L18- Characteristics of Tumours Flashcards
What is Cancer?
Cancer is the uncontrolled growth of cells, which can invade and spread to distant sites of the body
What is a tumour?
Historically – an abnormal swelling
Synonymous with Neoplasm
What is a Neoplasm?
Lesion resulting from the autonomous growth or relatively autonomous abnormal growth of cells that persists in the absence of the initiating stimulus
(abnormal growth of tissue, and when also forming a mass is commonly referred to as a tumor or tumour….This abnormal growth (neoplasia) usually but not always forms a mass)
What is Histiogenesis
The differentiation of cells into specialised tissues and organs during growth from undifferentiated cells (the 3 primary germ layers)
Tumours are usually named in relation to where they are found: Epithelial cells
carcinomas
Tumours are usually named in relation to where they are found: Connective tissues
sarcomas
Tumours are usually named in relation to where they are found: Lymphoid/haematopoietic organs
lymphomas/leukaemias
What are tumours characterised by?…(3 things)
Differentiation
Rate of Growth
Local Invasion
Metastasis
Do Malignant tumours tend to grow more rapidly than benign tumours?
Many exceptions to this rule
Not useful to discriminate
Different malignancies show varied growth rates
◦ Slow growing tumours associated with long survival
◦ Rapidly-growing tumours lethal within a short time
Define Differentiation in terms of tumours
The extent that neoplastic cells resemble the corresponding normal parenchymal cells, morphologically and functionally
Comment on the differentiation between Benign and malignant tumours…
Benign tumours
◦ usually well-differentiated
◦ Mitoses are rare
Malignant neoplasms
◦ wide-range of parenchymal differentiation
◦ Most exhibit morphologic alterations showing malignant nature
What is Anaplasia?
Lack of differentiation in neoplastic cells
Well-differentiated tumors resemble their tissue of origin
poorly-differentiated or undifferentiated (anaplastic) tumor cells appear primitive and lack specialisation
(Tell tale sign of Malignancy)
What is Pleomorphism?
variability in the size, shape and staining of cells and/or their nuclei
Variation
◦ Size
◦ shape
Explain how you can differentiate Abnormal nuclei Morphology?
Nuclei appear too large for the cell that they are in
Variability in nuclear shape (irregular e.g look like faces)
Hyperchromatism (dark colour)
Abnormally large nucleoli
What are mitoses
Represent the chromosomes all lined up in metaphase
come up as long dark blobs when stained
An indication of proliferation
Atypical, bizarre mitotic figures seen in malignancy:
◦ Tripolar
◦ Quadripolar
◦ Multipolar spindles
Summary of Differentiation: Meaning of Well differentiated
◦ Closely resembles normal tissue of origin
◦ Little or no of evidence of anaplasia
◦ BENIGN and occasional malignant
Summary of Differentiation: Meaning of Moderately differentiated
◦ Somewhere in between
Summary of Differentiation: Poorly differentiated
◦ Little resemblance to tissue of origin
◦ Highly anaplastic appearance
Summary of Differentiation: Undifferentiated / anaplastic
◦ Cannot be identified by morphology alone
◦ Molecular techniques
Grades are related to differentiation, talk about the different grades…1, 2, 3
◦ Well differentiated = low grade / grade 1
◦ Moderately differentiated = intermediate / grade 2
◦ Poorly differentiated = high grade / grade 3
Changes in function can occur in Tumours of cells: What are the clinical clues?
e.g Can secret excess hormones
Increased levels in blood can be used to detect and to follow up tumours
Some express proteins only normally found in other adult cells
Some tumours express foetal proteins not seen in adults
Why are malignant local invasions difficult to treat?
Penetration of organ surfaces and skin
Surgical resection difficult
Requires resection of adjacent macroscopically normal tissue (margin)
What is Metastasis
Spread of a tumour to sites physically discontinuous with the primary tumour
Reduces life expectancy significantly
Metastasis is generally associated with..
◦ Lack of differentiation
◦ Local invasion
◦ Rapid growth
◦ Large size
