BIOC33H3 Lecture Notes - Histology, Cellular Differentiation, Oncogene
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Chapter 16: Cancer
Cancer encompasses a broad range of diseases of multiple causes that can arise in any cell of
the body capable of evading regulatory controls over proliferation and differentiation.
Two major dysfunctions present in the process of cancer are (1) defective cellular proliferation
(growth) and (2) defective cellular differentiation.
Cancer cells usually proliferate at the same rate of the normal cells of the tissue from which they
arise. However, cancer cells divide indiscriminately and haphazardly and sometimes produce
more than two cells at the time of mitosis.
Protooncogenes are normal cellular genes that are important regulators of normal cellular
processes. When these genes become mutated, they can begin to function as oncogenes
Tumors can be classified as benign or malignant.
o Benign neoplasms are well-differentiated.
o Malignant neoplasms range from well-differentiated to undifferentiated.
The stages of cancer include initiation, promotion, and progression.
o The first stage, initiation, is the occurrence of a mutation in the cell’s genetic structure,
resulting from an inherited mutation, an error that occurs during DNA replication, or
following exposure to a chemical, radiation, or viral agent.
o Promotion, the second stage in the development of cancer, is characterized by the
reversible proliferation of the altered cells.
o Progression, the final stage, is characterized by increased growth rate of the tumor,
increased invasiveness, and spread of the cancer to a distant site (metastasis).
Since cancer cells arise from normal human cells, the immune response mounted against cancer
cells may be inadequate to effectively eradicate them.
The process by which cancer cells evade the immune system is termed immunologic escape.
Tumors can be classified according to anatomic site, histologic (grading), and extent of disease
o In the anatomic classification of tumors, the tumor is identified by the tissue of origin,
the anatomic site, and the behavior of the tumor (i.e., benign or malignant).
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