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Biology 207
1/23/02
Biology of Cancer
Lecture 3 "Cancer types and stages"
Reading: Chapter 2, Cooper
Lecture Outline:
1. Tumor initiation and progression
2. Classification of cancers
3. Clinical staging
Lecture notes:
1. Tumor initiation and progression: Fig. 2-2 Cooper
"Multistep model of carcinogenesis"
Key changes that occur in cancer cells

Mutation--alter DNA sequence of key cancer genes. Usually around 6
genes are changed.

Selection--survival of most rapidly reproducing cells.
Major changes that take place in conversion of benign tumor to metastatic
tumor.
Neoplasm=tumor=abnormal growth of cells

Benign tumor--confined to its original location.

Metastatic tumor--frequently also malignant (leads to death); spreads to
other tissues and organs of the body.
Example: Colon cancer, Fig. 2-3 Cooper depicts stepwise progression of
epithelial cancer from single cell to metastasis (cancer spread).
2. Cancer classification

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There are >100 different types of cancers.
Arise from abnormalities in cell growth and division.
Originate from different types of normal cells.
Vary in rates of growth and ability to spread.
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Classification of cancers based on cell/tissue origin
Carcinomas: cancers of epithelial cells.

Epithelia: cell that cover surfaces, for example skin, lining of digestive
tract. Glands also are epithelia.

Make up 90% of human cancers.
Sarcomas: tumors of connective tissues.

Connective tissues lie below epithelia and hold things together or support
the body. Some examples are muscle and bone.

Cancers are rare, because these cells do not reproduce very often.
Leukemias and Lymphomas: Cancers of blood cells.
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Leukemias are cancers of circulating blood cells or stem cells of the bone
marrow.
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Lymphomas are usually solid tumors in lymphatic organs (system that
cleanses the blood).
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Comprise 8% of all human cancers.
Further classification of cancers
(1) site of origin: lung, breast carcinomas
(2) cell type: squamous cell carcinoma: cancer of flat epithelial cell

Skin cancer: 3 types
o Basal cell carcinoma
o Squamous cell carcinoma

Account for 90% of skin cancers; cure rates 99%; rarely
metastasize.
o Melanoma--Cancer of pigment forming cells. Can metastasize
rapidly. Fatal to 20% of patients.
Cancers of glands: prefix adenoExample adenocarcinoma
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Cancers of embryonic tissues: suffix -blastoma
Neuroblastoma: Childhood cancer of neurons.
Retinoblastoma: Childhood eye cancer.
Historical names: Named after discoverer
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Wilm's Tumor (a childhood kidney cancer)
Hodgkin's disease (a type of lymphoma)
Kaposi's sarcoma (cancer of blood vessels, rare except associated with
immunodeficiency and HIV infection)
3. Clinical staging of cancer
a. Staging specific to particular types of cancer, e. g. prostate cancer
b. Universal system: "TNM system"

Developed by US and International committees

Based on 3 considerations
o T = condition of primary tumor (values usually T1-T4)
o N = extent of lymph node involvement (values N0-N2)
o M = extent of distant metastasis (values M0 or M1)
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Correlation between tumor staging and prognosis/treatment
o T low stage, no lymph node involvement, good cure rate
o T high stage, lymph nodes involved, metastasis, poor survival rate
Example: TNM staging of colon cancer, Table 2.2 Cooper
Stage
T1N0M0
T2N0M0
T3N0M0
T4N0M0
T3N1M0
T4N1M0
Five year survival rate for colon cancer
Survival rate (5 yr)
~90%
~80%
~60-70%
~50%
~40%
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For early stage:
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For T3, T4, N1 or N2: radiation and/or chemotherapy useful in addition to
surgery
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M1 stage:
surgery usually leads to cure
No longer curable; treatments can prolong life
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