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Biology of Cancer
This is a brief overview from Chapter 11 in McCance and Huether Pathophysiology.
The chapter must be read in it’s entirety to get a grasp on the information contained
therein.
Cancer: Greek word for crab, Karkinoma
.
Tumor: originally referred to any swelling, now reserved for describing a new growth
or neoplasm.
 Benign tumors: usually incapsulated and well-differentiated
o Retain some normal tissue structure
o Do not invade the capsules surrounding them
o Do not spread to regional lymph nodes or distant locations
o Generally named according to the tissues from which they arise and
include the suffix “oma”.
 Malignant tumors: distinguished from benign tumors by:
o More rapid growth rates
o Specific microscopic alterations, including loss of differentiation and
absence of normal tissue organization.
o Lack a capsule
o Invade nearby blood vessels. Lymphatic and surrounding structures
o Spread to distant locations (metastasis).
o Most important characteristic is their ability to spread far beyond the
tissue of origin
o One of the hallmarks of cancer cells as seen under a microscope is
anaplasia (loss of cellular differentiation, irregularities of the size and
shape of the nucleus and loss of norm tissue structure.
In general, cancers are named according to the cell type from which they
originate:
o Carcinomas: arising in epithelial tissues
o Adenocarcinomas: arising from ductal or glandular structures
o Sarcomas: arising from connective tissue
o Lymphomas: cancer of lymph tissue
o Leukemias: cancers of blood-forming cells
See Table 11-2 on page 336 for Nomenclature and Classification list.
Cancer cells show:
o
o
o
o
o
o
Transformation
Autonomy
Anchorage-independent
Immortality
Anaplasia
Pleomorphic ability
Some causes of Cancer
o Viral (e.g.: HBV, HCV, EBV, KSHV, HPV)
o Bacterial (e.g.: Helicobacter pylori or H. pylori)
o Environmental risk factors: tobacco us, Ionizing Radiation, Ultraviolet Radiation,
Alcohol Consumption, Sexual and reproductive behavior, Air pollution,
electromagnetic fields
o Occupational hazards (asbestos)
o Diet
o Obesity
o Genetic factors
Tumor Invasion and Metastasis
Tumor spread through:
o Direct invasion of continuous organs (local spread)
o Metastases to distant organs by way of lymphatics and veins
o Metastases by way of implantation
Four phases of progression of malignant tumors:
o Transformation: malignant change in initiating cell
o Growth of transformed cell
o Local invasion
o Distant metastasis
Clinical manifestations of cancer
o Pain: early stages, little or no pain, 60-80% of those with terminal cancer
experience pain.
o Caused by: pressure, obstruction, invasion of a sensitive structure,
stretching of visceral surfaces, tissue destruction, and inflammation.
o Fatigue: most frequently reported symptom
o Cachexia: most severe form of malnutrition associated with cancer; syndrome
includes anorexia, early satiety, weight loss, anemia, asthenia, taste alterations,
and altered protein, lipid, and carbohydrate metabolism.
o Anemia: common disorder associated with malignancy.
o Leukopenia and thrombocytopenia: by direct tumor invasion to the bone marrow
o Infection: the most significant cause of complications and death in persons with
malignant disease.
Cancer treatment
o Chemotherapy: includes any medicinal agent having antitumor effect.
o Single agent chemotherapy: initial attempts to treat cancer centered on
this, agents known to have significant early response rates, but duration of
response was short lived.
o Combination chemotherapy: synergistic use of several agents, each of
which individually has an effect against a certain cancer.
o Principle of dose intensity: direct correlation between dose of a
chemotherapeutic agent and killing of tumor cells.
o Therapeutic index: relative effective dose needed to kill cancer cells as
compared to the dose that would be harmful to normal cells.
o Primary or neoadjuvant chemotherapy: the early use of agents before
definitive local control with surgery or irradiation to decrease the initial
tumor size.
o Radiation: goals of ionizing radiation:
o to eradicate cancer without producing excessive toxicity during treatment
o To avoid damage to normal structures
o Surgery: objectives:
o Biopsy of tumor with intraoperative staging and sentinel node localization
and biopsy.
o Curative resections (if distant metastasis not evident)
o Debulking surgery: majority of tumor removed, allowing for increased
success of adjuvant chemotherapy or irradiation.
o Hormonal therapy: mechanism of action to include receptor activation or
blockade, which interferes with intercellular growth and proliferation signaling
cascades.
o Immunotherapy: biologic response modifiers (BRMs):
o Direct cytotoxic effect on cancer cells
o Initiation or augmentation of host’s tumor-immune rejection response
o Modification of cancer cell susceptibility to the lytic or tumor-static
effects of the immune system.
o Immunomodulating agents
o Interferons
o Antigens
o Effector cells and lymphokines
o Monoclonal antibodies
Side Effects of Cancer Treatment
o Gastrointestinal Tract
o Oral ulcers (stomatitis), malabsorption, diarrhea, increased risk of
infection, especially by person’s own GI flora, nausea.
o Bone Marrow
o Suppression of all three cell lines
o Hair and Skin
o Alopecia, usually temporary (and not all agents cause)
o Decreased renewal rates of epidermal layers may lead to skin breakdown
and dryness, erythema (caused by radiation).
o Reproductive tract
o Affect gametes, lead to varying degrees of decreased fertility and
premature menopause.
There are an overwhelming abundance of cancer sites on the web (Millions!)
Here are a few if you feel the need to explore…..
www.cancer.org
www.asco.org
www.cancer.gov
www.komen.org
www.cancerhelp.org
For excellent cell pictures: http://www.rkm.com.au/imagelibrary/index.html
www.chemheritage.org/educationalservices
References
McCance, K., & Huether, S., (2006). Pathophysiology The Biologic Basis for Disease in
Adults and Children (5th ed.). St. Louis: Elsevier.
Magic Bullets: Chemistry vs. Cancer. Retrieved November 1, 2006, from
http://www.chemheritage.org/educationalservices/pharm/chemo/readings/timeline.htm