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Introduction to cancer
Cancer (medical term: malignant neoplasm) is a class
of diseases in which a group of cells display uncontrolled
growth (division beyond the normal limits), invasion (intrusion
on and destruction of adjacent tissues), and
sometimes metastasis (spread to other locations in the body via
lymph or blood).
Important terms associated with cancer:
Tumor : Also called neoplasm describes an abnormal proliferation of
genetically altered cells.
Cancer causing agents are called carcinogens.
The branch of medicine concerned with the study, diagnosis, treatment, and
prevention of cancer is oncology.
Metastasis: new tumors that appear far from the original tumor.
Normal cell cycle
divides
grows
functions
apoptosis
death
Apoptosis : programmed cell death that happens in all normal cells, but not in cancer cells
Cancer cell cycle
divides
grows
immortal
tumor
Cancer tumors
Benign
self-limited,
do not invade or metastasize
Malignant
Invasive
metastasize
Cancer causes
Environmental:
Chemicals
Radiations
Pollutants
Genetic factors
Genetics of cancer
Oncogenes
Tumor suppressor genes
Protooncogenes present in all
humans, get switched on in some
people causing cancer
Present in all humans, prevent
tumor, but are silenced in some
people causing cancer
Classification of cancer
Cancers are classified by the type of cell that resembles the tumor and,
therefore, the tissue presumed to be the origin of the tumor. These are the
histology and the location, respectively.
Examples of general categories include:
Carcinoma: Malignant tumors derived from epithelial cells. This group
represents the most common cancers, including the common forms
of breast, prostate, lung and colon cancer.
Sarcoma: Malignant tumors derived from connective tissue,
or mesenchymal cells.
Lymphoma and leukemia: Malignancies derived from
hematopoietic (blood-forming) cells.
Germ cell tumor: Tumors derived from totipotent cells. In
adults most often found in the testicle and ovary; in fetuses,
babies, and young children most often found on the body
midline.
Blastic tumor or blastoma: A tumor (usually malignant)
which resembles an immature or embryonic tissue. Many of
these tumors are most common in children.