Two types of Skin Cancer:
Melanoma
* Cancer of pigment cells of skin melanocytes
Non - Melanoma
* Cancer of skin cells; keratinocytes
BCC (Basal Cell Carcinoma)
SCC (Squamous Cell Carcinoma)
Skin Cancer: Magnitude of the Problem (NON - MELANOMA)
* Non - Melanoma
1/3 of all cancers diagnosed in the US each year
BCC (Basal Cell Carcinoma)
12 million diagnosed each year
Skin Cancer: 1990
*60,000 Skin Cancers
| # Of Cancers |
Death per year |
| 500 K BCC |
<100 (.02%) |
| 100K SCC |
2500 (2.5%) |
| 27 K MM |
6300 (23%) |
| HIV |
15,000 |
Basal Cell Carcinoma
- The most common diagnosed cancer in the US
- 99% of people developing BCC are White
- 95% of BCC occur between 40-70 years old
- 85% of BCC occur on the head & neck
- Etiology of BCC: Sun exposure
- Biology of BCC:
- locally aggressive and destructive
- does not metastasize (<.02%)
BCC Types:
- Nodular BCC (50%) "rodent ulcer"
- Pigmented BCC (6%) pearly pigmented
- Superficial BCC (10%) red scaling rash
- Morpheaform BCC (2%) scar like
- *Never let BCC go without treatment
- *BCC may reoccur
Squamous Cell Carcinoma
- Etiology of SCC: Sun exposure
- Precursor lesion: Actinic keratosis
- Biology of SCC:
- locally aggressive and destructive
- does metastasize: 0.5-3% of SCC of skin
*SCC in situ - Bowen's Disease
Melanoma:
- Etiology: Acute and chronic sun exposure
- Cell of origin: Melanocyte
- Precursor of melanoma: none most often
- Biology of melanoma:
- metastasizes often unless removed early
- starts in skin at dermo-epidermal junction as an abnormal melanocyte
Characteristics of Melanoma Patients
Race
White skin 98%
Black skin 1%
Other (Hispanic, Asian) 1%
Presenting Stage
Stage I or II (localized disease) 87%
Stage III (regional metastases) 10%
Stage IV (distant metastases) 3%
- Sun damaged skin - uniform melanocytes
- Melanoma in situ - melanoma in epidermis
- Melanoma-thin invasive type - early invasion into dermis
Stages in the Evolution of Melanoma:
| MM in situ |
very rare |
metastases - <1% |
| Thin MM 1-2 mm Breslow |
rare |
metastases - 5% |
| Thick MM 2-3 mm Breslow |
more frequent |
metastases -18% |
ABCD's of Melanoma:
A - Asymmetry (not round or oval)
B - Border (irregular, notched)
C - Color (black, dark brown, FLAG)
D - Diameter (>6mm, 1/4 inch)
*Any change in an existing mole is not a good sign
Effects of Chronic Sun Exposure
Atrophy of skin & telangiectasia
Actinic ("senile") purpura - (bruising)
Fragility (easy tearing of skin)
Wrinkles (fine wrinkles, "crows fee")
Solar Elastosis (yellow 'bumps' on skin)
Solar Lentigos ("liver spots")
Actinic Keratosis / Skin Cancers
Photocarcinogenesis:
****How does light cause skin cancer?
Skin cancers are associated with chronic ultraviolet light (UV) exposure
The most effective wavelengths that cause cancer are in the UV wavelengths
290-320 nm = UVB
Dose Response:
Repeated exposure over the animals life is cumulative (total lifetime
dose of light)
Increasing the amount of UVL exposure
decreases the time to produce skin cancers
increases the numbers of skin cancers
Common Myths About Sun Exposure:
"I don't get sun exposure except weekends and vacations"
Everyone gets some sun exposure everyday
This exposure represents 10-40min/day
You get this 365 days a year
A component of this exposure leaves permanent changes in the DNA in the
skin and is irreversible
A tan protects you from the damaging effects of the sun
A tan marks those who have had large amounts of sun exposure on a regular
basis
This sun exposure leaves permanent changes in the skin
A tan does increase the MED of the skin; and does protect against burns;
but leaves damage
A tan is healthy
A small amount of sun is required to make Vitamin D
A tan marks a person who has had intermittent sun (UVB) exposure. This
person has developed permanent damage in the skin that takes 10-20 years to
manifest itself. This leads to atrophy of the skin and skin cancer,
"I don't see any damage"
the damage is cumulative even if you don't see it
the consequences of the damage takes 10-20 years to become evident
most commonly, thin wrinkled skin, fragility
what most think of as aging of the skin is for the most part chronic sun
damage
skin cancer BCC, SCC usually occurs after 40 years old
Melanoma: most often starts to occur in the 20-30's
Tanning with long wave UVL (UVA) in a tanning booths
UVA (320-400 nm) does not induce the same type of tan as does UVB (200-320
nm)
UVA does not directly damage the DNA like UVB
UVA may account for deep damage to skin
There is UVB produced by UVA bulbs
Skin types and Responses to Sun
Minimal Erythematous Dose (MED)
The dose of light that causes marginated erythema (redness) after 24 hours.
Sun protective factor = SPF
Time to MED with sunscreen
Time to MED without sunscreen
EX: 80 min with sunscreen
10 min without sunscreen = 8 SPF
How to minimize the effect of Sun Exposure:
Avoid sun exposure in the middle of the day
Wear as much protective clothing as possible
Sunscreens - SPF > 20
Response to 3 MED Noon Sun:
| Skin Type |
Burn |
Tan |
| I |
always |
never |
| II |
usually |
with difficulty |
| III |
sometimes mild |
average |
| IV |
almost never |
easily |
| V |
very rare |
profusely |
| VI |
never |
darkens |
Sunscreen Photoprotection
Industry has said that an adequate application requires 2mg/cm of cream
In real life only 1/4 the optimal amount is applied to skin
Sunscreen with a SPF 40=10
Sunscreen with a SPF 20=5