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
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 (tumor-inducing genes).
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
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
Tumors can be classified according to anatomic site, histologic (grading), and extent of
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).
o In histologic grading of tumors, the appearance of cells and the degree of
differentiation are evaluated pathologically. For many tumor types, four grades
are used to evaluate abnormal cells based on the degree to which the cells
resemble the tissue of origin. o The staging classification system is based on a description of the extent of the
disease rather than on cell appearance.
The biopsy procedure is the only definitive means of diagnosing cancer.
The goal of cancer treatment is cure, control, or palliation.
o When cure is the goal, the treatment offered is expected to have the greatest
chance of disease eradication and may involve local therapy (i.e., surgery or
radiation) alone or in combination with or without periods of adjunctive systemic
therapy (i.e., chemotherapy).
o Control is the goal of the treatment plan for many cancers that cannot be
completely eradicated but are responsive to anticancer therapies and, as with other
chronic illnesses such as diabetes mellitus and heart failure, can be managed for
long periods of time with therapy.
o With palliation, relief or control of symptoms and the maintenance of a
satisfactory quality of life are the primary goals rather than cure or control of the
Modalities for cancer treatment with all three goals include surgery, chemotherapy,