Cancer screening is the process of looking for cancer before a person has any symptoms. It involves testing people who are at increased risk of developing cancer, as well as those who have no symptoms but may be at risk due to their age, family history, or lifestyle choices. The goal of cancer screening is to detect cancer early when it is most treatable. There are several types of cancer screening tests, including imaging tests like mammograms and CT scans, blood tests, and genetic tests. While these tests can be helpful in detecting cancer, they are not perfect and can sometimes give false-positive or false-negative results. Your doctor will work with you to determine which screening tests are appropriate for your individual situation.

1. 23.1 Cancer Is a Group of Diseases
Characterized by Cell Proliferation

2. Tumor Formation: A Distinct Mass of
Abnormal Cells
• Benign tumor: the tumor remains localized.
• Malignant tumor: tumor cells invade other
tissues.
• Metastasis: the tumor cells induce secondary
tumors.

3. Cancer as a Genetic Disease
• The clonal evolution of tumors
• The tumor cells acquire more mutations that
allow them to become increasingly more
aggressive in their proliferate properties.

5. Role of Environmental Factors in Cancer

7. 23.2 Mutations in a Number of Different
Types of Genes Contribute to Cancer

8. Oncogenes and Tumor-Suppressor
Genes
• Oncogene: dominant-acting stimulatory genes
that cause cancer
• Proto-oncogenes: responsible for basic cellular
functions in normal cells; when mutated, they
become oncogenes.

9. Tumor-Suppressor Genes
Inhibit cancer and recessive acting; when mutated,
normal cells become cancerous.

15. Genes That Control the Cycle of Cell
Division
•Checkpoints that halt cell division
•Initiators that act as signals to begin
cell divsion

17. • Signal-transduction pathways
• A cascade of intracellular reactions
• DNA repair genes
• Genes that regulate telomerase
• Inappropriate activation of telomerase may
lead to cancer.
• Genes that promote vascularization and the
spread of tumors

18. 23.3 Changes in Chromosome Number and
Structure Are Often Associated with Cancer
• Example:
A reciprocal translocation between
chromosome 9 and 22 causes chronic
myelogenous leukemia.

20. 23.4 Viruses Are Associated with Some
Cancers
• Retroviruses cause cancer by
• mutating and rearranging proto-oncogenes
• inserting strong promoters near proto-
oncogenes

23. 23.5 Changes in DNA Methylation Are
Often Associated with Cancer
• Epigenetic process:
• Reversible genetic alterations

24. 23.6 Colorectal Cancer Arises Through the
Sequential Mutation of a Number of Genes