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25-5
Cancer
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What is cancer?Cancer is defined as the continuous
uncontrolled growth of cells.
A tumor is a any abnormal proliferation of cells.Benign tumors stays confined to its original
locationMalignant tumors are capable of invading
surrounding tissue or invading the entire body
Tumors are classified as to their cell typeTumors can arise from any cell type in the body
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Cancer is an umbrella term covering a numerous conditions characterized by unscheduled and
uncontrolled cellular proliferation Almost any mammalian organ and cell type can
succumb to cancer
The causes of cancer are many and varied, and include genetics, environmental influences, infectious agents and ageing. These transform normal cells into cancerous ones
The complexity of the disease that has hampered the development of effective and specific cancer therapies.
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Cancer cells have abnormal cell cycles divide excessively and form tumors
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Breast cancer cell - altered morphology
Figure 8.10x1
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A kidney tumour
A kidney carcinoma (the blob at the top)
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Lung Cancer
x-rayx-ray Squamous Squamous carcinomacarcinoma
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Colon Cancer
X-rayX-ray GrossGross MicroscopicMicroscopic
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Heterogeneous size and shape of cancer cells and cancer cell nuclei
Heterogeneous size and shape of cancer cells and cancer cell nuclei. The nuclear heterogeneity reflects the genetic instability.
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Cancer continued3 cancer types
Carcinomas; constitute 90% of cancers, are cancers of epithelial cells
Sarcomas; are rare and consist of tumors of connective tissues (connective tissue, muscle, bone etc.)
Leukemias and lymphomas; constitute 8% of tumors. Sometimes referred to as liquid tumors. Leukemias arise from blood forming cells and lymphomas arise from cells of the immune system (T and B cells).
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Properties of cancer cells
Normal cells show contact inhibition
Cancer cells lack contact inhibition
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Properties of cancer cellsThey keep growing
And growing
And growing
And growing
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Cancer Incidence and Death Rates
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Cancer
Cells in culture and in vivo exhibit contact-inhibition
Cancer cells lack contact inhibition feedback mechanisms. Clumps or foci develop.
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Cancer GradeAlternate term “tumor grade”Based on microscopic features
(cytology or histology)
low grade moderate high
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Early detection is the key!
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What causes Cancer?Genetic mutations
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What is the source of oncogenes?
Mutation of a normal gene = change in DNA sequence
UV light, Xrays, natural or synthetic chemicals
Virus (ex. HPV and cervical cancer)
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How do normal cells become cancerous?
Selection within tumor for “most cancerous” cells
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Cancer: Benign
• Benign: localized and of small size
• Cells that closely resemble, and may function, like normal cells
• May have a fibrous capsule around the cells
• Become problems due to sheer bulk or due to secretions (e.g. hormones)
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Malignant tumors: high rate of division, properties may vary compared to cells of origin. Most malignant cells become metastatic
Invade surrounding tissue and establishment of secondary areas of growth: Metastasis
Cancer : Malignant
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Malignant tumors can invade other tissues and may kill the organism
Tumor
Figure 8.10
Glandulartissue
1 2 3A tumor grows from a single cancer cell.
Cancer cells invade neighboring tissue.
Lymphvessels
Cancer cells spread through lymph and blood vessels to other parts of the body.
Metastasis
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Growth pattern
Benign Malignant
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MetastasisCarcinoma: derived from endoderm or ectoderm
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Events in Metastasis.
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Angiogenesis
Cancer cells block the formation of new blood vessels that bring necessary nutrients and oxygen to the hungry tumor cells
This forms a network of new blood vessels!
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24.1 Benign tumors arise with great frequency but pose little risk because they are localized and small
Figure 24-1
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24.1 Malignant tumors generally invade surrounding tissue and spread throughout the body
Figure 24-2
Alterations in cell-cell interactions and the formation of new blood vessels are associated with malignancy
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DNA from tumor cells can transform normal cultured cells
Figure 24-3
Cells that continue to grow when normal cells have stopped are said to be transformed
Transformed cells may exhibit many of the properties of malignant tumor cells
normal transformed