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Washington and Leaver Chapter 36 Radiation Therapy Notes
- Course
- RADT (RAD242)
- Institution
- Wallace State Community College Hanceville
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Principles and Practice IIChapter 36:
Cancer of the skin is the most common form of malignancy in humans
Nonmelanoma skin cancers (NMSC) represent 1/3rd of all cancers
- Cutaneous squamous cell carcinoma (cSCC) represents 20% of all NMSC
- The total number and incidence rate of NMSCs cannot be accurately recorded because
reporting to cancer registries is not required
Melanoma incidence rate has increased faster than that of any other cancer
Malignant melanoma is the deadliest form of skin cancer
Melanoma is 20 times more common in whites than African Americans
Tendencies for people to develop skin cancer and melanomas categories:
1) Geographic location (equator)
2) Skin type (fairer skin)
3) Multiplicity (prior skin cancer occurrence; previous melanoma of the skin increases the
risk of another primary melanoma)
4) Gender (women get melanoma younger, men triple women’s rates by age 80)
American Cancer Society expects that 90% of all skin cancers would be prevented if people
protected their skin from the sun
People who spend most time in the sun such as farmers and construction workers develop basal
cell carcinoma (BCC) and squamous cell carcinoma (SCC)
UVA and UVB are thought to be two types of UV rays harmful to the skin
- UVB damages DNA and its repair systems
Most skin cancers appear after age 50, but the damaging effects of the sun's rays are accumulated
over a lifetime
Arsenic and radiation exposure are also carcinogens
Xeroderma pigmentosum and basal cell nevus syndrome are genetic disorders associated with
the formation of BCC
Basal cell nevus syndrome:
- Cysts of the jaw bones
- Pitting of the palms and soles
- Skeletal abnormalities (especially ribs)
SCCs have been associated with:
- HPV
- Weakened immune system
- Rare genetic disorders
- Scars or chronic inflammatory conditions
, - Hydrocarbons from coal and petroleum
- Areas of chronic drainage (sinuses, fistulas, etc.)
Smoking is proven to cause SCC of the lip
Melanomas develop from melanocytes which grow in clusters to form moles or nevus’
- Congenital melanocytic nevi: mole present at birth
o Small, medium, large
- Common acquired nevi: mole that develops later in life
Melanocytic nevi grouped into 3 categories:
1) Junctional
2) Compound
3) Intradermal
The propensity of a mole to develop into melanoma is related to the location of the melanocytic
clusters found in the moles
Intradermal nevi rarely turn into melanoma, junctional is far more common
Melanocytes in junctional and compound nevi are closer to the skins surface and receive higher
amounts of melanoma-inducing UV radiation
Dysplastic nevi (aka atypical moles) are acquired pigmented lesions of the skin that have 1 or
more clinical feature of melanoma, which are
1) Asymmetry
2) Border irregularity
3) Color variation
4) Diameter greater than 6mm
People with a family history of melanoma have an eightfold increased risk of development
Dysplastic nevus syndrome:
1) Occurrence of melanoma in first-degree or second-degree relative
2) Large number of moles
3) Moles that have certain histologic features
The skin is the largest organ in the body, its functions being body temperature regulation, natural
barrier (epithelial membrane), produces vitamin D, provides receptors for external stimuli
Epidermis: most superficial, epithelial layer, extremely thin, composed of layers
- Stratum Basale (produces keratinocytes)
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