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skin
cancer
Skin cancer is a malignant growth on the skin,
which can have many causes, including repeated severe sunburn or
long-term exposure to the sun. Skin cancer generally develops in the
epidermis, the outermost layer of skin, so a tumor is usually clearly
visible. This makes most skin cancers detectable in the early stages.
There are three common types of skin cancer each of which are named
after the type of skin cell. In the case of UV damage, sun screen is
one of the better forms of prevention.
Types
The most common types are basal cell carcinoma (BCC) and
squamous cell carcinoma (SCC) which may be locally disfiguring but
unlikely to spread to other parts of the body. The most dangerous type
is malignant melanoma, which can be fatal if not treated early, but
forms only a small proportion of all skin cancers.
Other types of skin cancer are:
Dermatofibrosarcoma protuberans
Merkel cell carcinoma
Kaposi's sarcoma
Prevalence
Skin cancer is an increasingly common condition, in part
attributed to increased exposure to ultraviolet radiation. The
increased exposure is mainly due to the recent popularity of sun
tanning (sun bathing). Lighter-skinned individuals are more
vulnerable. In the United States, about one out of every three new
cancers arises from skin. Skin cancers are often curable. Barriers
which reduce UV exposure are effective in preventing skin cancers
(clothes, hats, creams, lotions).
Prognosis
Minor surface skin cancers are readily treatable by simple
surgery, but if the cancer is allowed to grow then it will penetrate
through the layers of skin and affect the lymphatic system. It may
also metastasize and spread to other parts of the body.
Skin cancers which are aggressive, recurrent, or located upon 'high
risk sites' of the body (central face, scalp, ears, genitalia) may
require more advanced surgical approaches such as Mohs' micrographic
surgery to achieve high cure rates.
Signs and symptoms
There are a variety of different skin cancer symptoms.
These include sores or changes in the skin that do not heal, ulcers in
the skin, discoloring in parts of the skin, and changes in existing
moles.
Basal cell carcinoma usually looks like a raised, smooth, pearly bump
on the sun-exposed skin of the head, neck or shoulders. Sometimes
small blood vessels can be seen within the tumor. Crusting and
bleeding in the center of the tumor frequently develops. It is often
mistaken for a sore that does not heal.
Squamous cell carcinoma is commonly a red, scaling, thickened patch on
sun-exposed skin. Ulceration and bleeding may occur. When SCC is not
treated, it may develop into a large mass.
Most melanomas are brown to black looking lesions. Signs that might
indicate a malignant melanoma include change in size, shape, color or
elevation of a mole. The appearance of a new mole during adulthood, or
new pain, itching, ulceration or bleeding of an existing mole should
be checked.
Prevention
Non-melanoma skin cancer
Non-melanoma skin cancers include basal cell carcinoma and squamous
cell carcinoma.
reducing exposure to ultraviolet (UV) radiation
changing patterns of outdoor activities, sun exposure avoidance 11 am
- 3 pm
wearing protective clothing (long sleeves and hats) when outdoors
using efficient sunscreens is recommended. It is a simple step to
reduce your chance of cancer. You should wear some type of sunscreen
everyday.
Melanoma
avoiding sunburns, especially in childhood and adolescence
reducing exposure to ultraviolet (UV) radiation
changing patterns of outdoor activities, sun exposure avoidance 10 am
- 4 pm
wearing protective clothing (long sleeves and hats) when outdoors
using sunscreen
It is generally accepted that UV exposure is the greatest risk factor
in melanoma development but skeptics have noted that there is
absolutely no proven data that links moderate sun exposure with the
appearance of melanoma.
Controversy
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This article has been tagged since January 2007.
There is a lot of controversy in the medical community regarding the
role of sunlight to skin cancer. Michael F. Holick, MD, PhD, a
professor at Boston University, based on research, advocates moderate
sun light exposure, which would facilitate vitamin D production in
human body, as a mean to prevent skin cancer, as well as other forms
of cancer. However, he was asked to resign his post in 2004 by
Department chair Barbara Gilchrest, MD, for presenting a view that
conflicts with that from American Academy of Dermatology that any
sunlight exposure would increase the risk of skin cancer.[1]
Pathology
Squamous cell carcinoma is a malignant epithelial tumor
which originates in epidermis, squamous mucosa or areas of squamous
metaplasia.
Macroscopically, the tumor is often elevated, fungating, or may be
ulcerated with irregular borders. Microscopically, tumor cells destroy
the basement membrane and form sheets or compact masses which invade
the subjacent connective tissue (dermis). In well differentiated
carcinomas, tumor cells are pleomorphic/atypical, but resembling
normal keratinocytes from prickle layer (large, polygonal, with
abundant eosinophilic (pink) cytoplasm and central nucleus). Their
disposal tends to be similar to that of normal epidermis:
immature/basal cells at the periphery, becoming more mature to the
centre of the tumor masses. Tumor cells transform into keratinized
squamous cells and form round nodules with concentric, laminated
layers, called "cell nests" or "epithelial/keratinous pearls". The
surrounding stroma is reduced and contains inflammatory infiltrate
(lymphocytes). Poorly differentiated squamous carcinomas contain more
pleomorphic cells and no keratinization.
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