1. Skin Cancer and Burns

2. Skin Cancer
One in five Americans develop skin cancer at some point. Most tumors that arise in the skin are benign and do not spread (metastasize) to other body areas. (A wart, a neoplasm caused by a virus, is one example.)
However, some skin tumors are malignant, or cancerous, and invade other body areas. A crucial risk factor for skin cancer is overexposure to the UV radiation in sunlight, which damages DNA bases. Adjacent pyrimidine bases often respond by fusing, forming lesions called dimers.
UV radiation also appears to disable a tumor suppressor gene [p53 or the patched (ptc) gene].
In limited numbers of cases, however, frequent irritation of the skin by infections, chemicals, or physical trauma seems to be a predisposing factor.

3. Basal Cell Carcinoma
Basal cell carcinoma (kar″sĭ-no′mah) is the least malignant and most common skin cancer; over 30% of all white people get it in their lifetime.
Stratum basale cells proliferate, invading the dermis and hypodermis. The cancer lesions occur most often on sun-exposed areas of the face and appear as shiny, dome-shaped nodules that later develop a central ulcer with a pearly, beaded edge.
Basal cell carcinoma is relatively slow-growing, and metastasis seldom occurs before it is noticed. Full cure by surgical excision is the rule in 99% of cases.

4. (a) Basal cell carcinoma.

5. Squamous Cell Carcinoma
Squamous cell carcinoma arises from the kerat-inocytes of the stratum spinosum.
The lesion appears as a scaly reddened papule (small, rounded elevation) that arises most often on the head (scalp, ears, and lower lip), and hands.
It tends to grow rapidly and metastasize if not removed. If it is caught early and removed surgically or by radiation therapy, chance of complete cure is good.

6. (b) Squamous cell carcinoma.

7. Melanoma
Melanoma (mel″ah-no′mah), cancer of melanocytes, is the most dangerous skin cancer because it is highly metastatic and resistant to chemotherapy.
It accounts for only about 5% of skin cancers, but its incidence is increasing rapidly (by 3–8% per year in the United States).
Melanoma can begin wherever there is pigment. Most such cancers appear spontaneously; about one-third develop from preexisting moles.
It usually appears as a spreading brown to black patch that metastasizes rapidly to surrounding lymph and blood vessels.
The key to surviving melanoma is early detection. The chance of survival is poor if the lesion is over 4 mm thick.
The usual therapy for melanoma is wide surgical excision accompanied by immunotherapy (immunizing the body against its cancer cells).

8. (c) Melanoma.

9. Burns
Burns are a devastating threat to the body primarily because of their effects on the skin.
burn is tissue damage inflicted by intense heat, electricity, radiation, or certain chemicals, all of which denature cell proteins and cause cell death in the affected areas.

10. Burns
The immediate threat to life resulting from severe burns is a catastrophic loss of body fluids containing proteins and electrolytes, resulting in dehydration and electrolyte imbalance.
These, in turn, lead to renal shutdown and circulatory shock (inadequate blood circulation due to reduced blood volume).
To save the patient, the lost fluids must be replaced immediately via the intravenous (IV) route.
In adults, the volume of fluid lost can be estimated by computing the percentage of body surface burned (extent of the burns) using the rule of nines.
This method divides the body into 11 areas, each accounting for 9% of total body area, plus an additional area surrounding the genitals accounting for 1% of body surface area. This method is only approximate, so special tables are used when greater accuracy is desired.

11. Estimating the extent and severity of burns.  
The extent of burns is estimated by using the rule of nines. Surface area values for the anterior body surface are indicated on the human figure. Total surface area (anterior and posterior body surfaces) for each body region is indicated to the right of the figure. Severity of burns depends on the depth of tissue damage.
In first-degree burns only the epidermis is destroyed.
In second-degree burns, the epidermis and part of the dermis are involved and blistering occurs.
In third-degree burns the epidermis and dermis (and often part of the hypodermis) are destroyed.

14. Sub-Chapter Test