Characteristics of tumours Flashcards
What is histiogenesis?
The differentiation of cells into specialised tissues and organs during growth from undifferentiated cells (the 3 primary germ layers)
What is histiogenesis relating to tumours?
Histogenic classification – classification of the tumour by the specific cell or tissue of origin
- Epithelial cells – carcinomas
- Connective tissues – sarcomas
- Lymphoid/haematopoietic organs – lymphomas/leukaemias
What is differentiation?
The extent that neoplastic cells resemble the corresponding normal parenchymal cells, morphologically and functionally
What are the characteristics of differentiation of benign tunours?
- usually well-differentiated
- Mitoses are rare
What are the differentiation characteristics of malignant tumours?
- Wide-range of parenchymal differentiation
- Most exhibit morphologic alterations showing malignant nature
What is anaplasia?
Neoplasms comprised of poorly-differentiated cells are described as anaplastic
“Telltale sign of malignancy”
What are the morphological changes that might occur during neoplasia?
- Pleomorphism
- Abnormal nuclear morphology
- Mitoses
- Loss of polarity
- Other changes
What is pleomorphism?
Variation - Size, shape Huge differences - Small cells with little differentiation - Large cells with one massive nucleus - Large cells with multinucleation
What abnormal nuclear morphology might be seen in cancer?
Nuclei appear too large for the cell that they are in Nuclear to cytoplasmic ratio -Can reach 1:1 rather than usual (1:4 or 1:6) Variability in nuclear shape -Irregular -Making pictures (raisins, faces etc.) Chromatin distribution -Coarsely clumped -Along cell membrane Hyperchromatism -Dark colour Abnormally large nucleoli
What are mitoses?
Atypical, bizarre mitotic figures seen in malignancy
- Tripolar
- Quadripolar
- Multipolar spindles
What are the features of loss of polarity?
- Orientation of cells disturbed
- Disorganised growth
What is the grade of a tumour related to?
Closely related to differentiation / clinical behaviour
Well differentiated = low grade / grade 1
Moderately differentiated = intermediate / grade 2
Poorly differentiated = high grade / grade 3
What is the stage of a tumour related to?
How far the cancer has spread throughout the body.
How is the level of differentiation within a tumour related to a possible change in function?
The better the differentiation of the tumour the better the retention of function i.e. a large, benign endocrine tumour may secrete large amounts of hormone.
What kinds of local invasion are associated with malignancies?
- Infiltration
- Invasion
- Destruction
What kinds of local invasion are associated with benign neoplasia?
- Cohesive expansile masses
- Localised to site of origin
- No capacity to infiltrate, invade or metastasise
What histological features might represent local invasion of a benign tumour?
- Rim of compressed fibrous tissue
- ECM deposited by stromal cells activated by hypoxia from pressure of tumour
- Tissue plane
- Discrete, moveable
- Easily palpable
- Easily excised
What are metastases?
Spread of a tumour to sites physically discontinuous with the primary tumour.
What are the pathways by which metastases can occur?
- Direct seeding
- Lymphatic spread
- Haematogenous spread
What is direct seeding?
Neoplasm penetrates a natural open field without physical barriers
Eg peritoneal cavity, pleural, pericardial, subarachnoid, joint spaces
Can remain confined to surface of peritoneal structures without penetrating
Eg pseudomyxoma peritonei
What is lymphatic spread?
Lymphatic Spread
Most common pathway
Tumours do not contain lymphatic channels
Lymphatic vessels at the tumour margins
What are sentinal nodes?
The first node in a regional lymphatic basin that receives lymph flow from the primary tumour
Identified by: injection of radiolabelled tracers/coloured dyes
Why might an enlarged node in a cancer patient not have cancer in it?
Drainage of tumour cell debris and tumour antigens induces reactive change in nodes
What are the features of haematogenous spread?
- Typical of sarcomas
- Also seen in carcinomas
- Veins more easily penetrated
- Blood-borne cells follow the venous flow draining site of the neoplasm
- Often come to rest in first encountered capillary bed
- Liver (portal) and lungs (caval) most frequently involved
