Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC), squamous-cell skin cancer (SCC) and melanoma. The first two, along with a number of less common skin cancers, are known as nonmelanoma skin cancer (NMSC). Basal-cell cancer grows slowly and can damage the tissue around it but is unlikely to spread to distant areas or result in death. It often appears as a painless raised area of skin, that may be shiny with small blood vessels running over it or may present as a raised area with an ulcer. Squamous-cell skin cancer is more likely to spread. It usually presents as a hard lump with a scaly top but may also form an ulcer. Melanomas are the most aggressive. Signs include a mole that has changed in size, shape, color, has irregular edges, has more than one color, is itchy or bleeds.
Greater than 90% of cases are caused by exposure to ultraviolet radiation from the Sun. This exposure increases the risk of all three main types of skin cancer. Exposure has increased partly due to a thinner ozone layer. Tanning beds are becoming another common source of ultraviolet radiation.For melanomas and basal-cell cancers exposure during childhood is particularly harmful. For squamous-cell skin cancers total exposure, irrespective of when it occurs, is more important. Between 20% and 30% of melanomas develop from moles People with light skin are at higher risk as are those with poor immune function such as from medications or HIV/AIDS. Diagnosis is by biopsy.
Decreasing exposure to ultraviolet radiation and the use of sunscreen appear to be effective methods of preventing melanoma and squamous-cell skin cancer. It is not clear if sunscreen affects the risk of basal-cell cancer. Nonmelanoma skin cancer is usually curable. Treatment is generally by surgical removal but may less commonly involve radiation therapy or topical medications such as fluorouracil. Treatment of melanoma may involve some combination of surgery, chemotherapy, radiation therapy, and targeted therapy. In those people whose disease has spread to other areas of their bodies, palliative care may be used to improve quality of life. Melanoma has one of the higher survival rates among cancers, with over 86% of people in the UK and more than 90% in the United States surviving more than 5 years.
Skin cancer is the most common form of cancer, globally accounting for at least 40% of cases. The most common type is nonmelanoma skin cancer, which occurs in at least 2-3 million people per year. This is a rough estimate, however, as good statistics are not kept. Of nonmelanoma skin cancers, about 80% are basal-cell cancers and 20% squamous-cell skin cancers. Basal-cell and squamous-cell skin cancers rarely result in death. In the United States they were the cause of less than 0.1% of all cancer deaths. Globally in 2012 melanoma occurred in 232,000 people, and resulted in 55,000 deaths. White people in Australia, New Zealand and South Africa have the highest rates of melanoma in the world. The three main types of skin cancer have become more common in the last 20 to 40 years, especially in those areas which are mostly Caucasian.
There are three main types of skin cancer: basal-cell skin cancer (basal-cell carcinoma) (BCC), squamous-cell skin cancer (squamous-cell carcinoma) (SCC) and malignant melanoma.
|Basal-cell carcinoma||Note the pearly translucency to fleshy color, tiny blood vessels on the surface, and sometime ulceration which can be characteristics. The key term is translucency.|
|Squamous-cell skin carcinoma||Commonly presents as a red, crusted, or scaly patch or bump. Often a very rapid growing tumor.|
|Malignant melanoma||The common appearance is an asymmetrical area, with an irregular border, color variation, and often greater than 6 mm diameter.|
Basal-cell carcinomas are present on sun-exposed areas of the skin, especially the face. They rarely metastasize and rarely cause death. They are easily treated with surgery or radiation. Squamous-cell skin cancer are common, but much less common than basal-cell cancers. They metastasize more frequently than BCCs. Even then, the metastasis rate is quite low, with the exception of SCC of the lip, ear, and in people who are immunosuppressed. Melanoma are the least frequent of the 3 common skin cancers. They frequently metastasize, and could potentially cause death once they spread.
Less common skin cancers include: dermatofibrosarcoma protuberans, Merkel cell carcinoma, Kaposi's sarcoma, keratoacanthoma, spindle cell tumors, sebaceous carcinomas, microcystic adnexal carcinoma, Paget's disease of the breast, atypical fibroxanthoma, leiomyosarcoma, and angiosarcoma.
BCC and SCC often carry a UV-signature mutation indicating that these cancers are caused by UVB radiation via direct DNA damage. However malignant melanoma is predominantly caused by UVA radiation via indirect DNA damage. The indirect DNA damage is caused by free radicals and reactive oxygen species. Research indicates that the absorption of three sunscreen ingredients into the skin, combined with a 60-minute exposure to UV, leads to an increase of free radicals in the skin, if applied in too little quantities and too infrequently. However, the researchers add that newer creams often do not contain these specific compounds, and that the combination of other ingredients tends to retain the compounds on the surface of the skin. They also add the frequent re-application reduces the risk of radical formation.
In the beginning, skin cell cancer can be painful, and they may appear as a pain that bleeds and oozes or otherwise something that does not heals. Even a minor trauma may result in bleeding of that bump. The skin bump has a central ulceration along with raised edges. The skin cancer symptoms include:
We often see that moles develop on the skin, but they are mostly harmless. Rarely a mole turns into skin cancer. If a mole does turn cancerous then it is melanoma. Individuals should take care and look out for any signs of differences in the mole’s color, symmetry or any other evolving changes. Therefore, it is obligatory to visit a physician or a dermatologist and get the abnormality examined.
Ultraviolet radiation from sun exposure is the primary environmental cause of skin cancer. Other risk factors that play a role include:
Many productive measures are present for treating skin cancer, but the choice of treatment chiefly depends on the size and location of the tumor. Treatment options can be broadly divided into medications and procedures. Medication includes several topical therapies and drugs which are injected or taken orally. Procedures comprise surgeries, radiation therapy, and laser and light-based treatments.
Few gels and creams are now used in superficial basal cell carcinomas which include imiquimod that works by invigorating the immune system through the production of interferon which eventually attacks the cancerous cells. Drugs are also used in combination of topical solutions.
Targeted therapies are a kind of novel drug combination where drugs such as cobimetinib and vemurafenib are taken orally along with advanced immunotherapies. Such therapies are currently gaining much attention in the treatment of advanced melanoma.
Chemical peel: Trichloroacetic acid is applied to repair superficial skin damage which peels the top skin layer. In general, normal skin regrows in a few weeks.
Cryosurgery: Liquid nitrogen is topically applied to the tumor growth causing the lesions to freeze. Later the lesion falls off naturally causing a temporary swelling and redness.
Curettage and Electrodesiccation: Curette, a small sharp ring-shaped instrument is used to scrape off the lesion and then cauterized using electrodesiccation. The applied heat destroys any residual lesion.
Excisional surgery: In this surgery, the physician removes the entire tumor along with some surrounding healthy tissue. Only after the lab confirms whether the tumor is present or not in the tissue beyond the safety margin, the physician declares the patient fit.
Laser surgery: Ablative lasers are used to remove the tissue without causing it to bleed. The laser gives the physician a better control in tissue removal.
Mohs Micrographic surgery: This technique is chiefly employed when preservation of unaffected tissue is vital. It is also employed when the tumor is poorly defined or after a recurrence of previously treated lesions. The very first layer of the tumor is removed and immediately assessed. The region demonstrating any residual microscopic tumor is then re-excised and re-evaluated. This procedure is further repeated till no tumor is seen.
Photodynamic therapy: A light-sensitizing agent is applied to the tumor and allowed to get absorbed in the skin. Then the physician uses a strong red or blue laser which selectively destroys the lesions by activating the medicated region.
Radiation therapy: Tumors are directly subjected to X-ray beams to treat cancerous lesions. It is employed when the tumors are hard to be removed or with immunosuppressed patients.
A malignant epithelial tumor that primarily originates in the epidermis, in squamous mucosa or in areas of squamous metaplasia is referred to as a squamous-cell carcinoma.
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.
A molecular factor involved in the disease process is mutation in gene PTCH1 that plays an important role in the Sonic hedgehog signaling pathway.
Non-invasive skin cancer detection methods include photography, dermoscopy, sonography, confocal microscopy, Raman spectroscopy, fluorescence spectroscopy, terahertz spectroscopy, optical coherence tomography, the multispectral imaging technique, thermography, electrical bio-impedance, tape stripping and computer-aided analysis.
Sunscreen is effective and thus recommended to prevent melanoma and squamous-cell carcinoma. There is little evidence that it is effective in preventing basal-cell carcinoma. Other advice to reduce rates of skin cancer includes avoiding sunburning, wearing protective clothing, sunglasses and hats, and attempting to avoid sun exposure or periods of peak exposure. The U.S. Preventive Services Task Force recommends that people between 9 and 25 years of age be advised to avoid ultraviolet light.
The risk of developing skin cancer can be reduced through a number of measures including decreasing indoor tanning and mid day sun exposure, increasing the use of sunscreen, and avoiding the use of tobacco products.
There is insufficient evidence either for or against screening for skin cancers. Vitamin supplements and antioxidant supplements have not been found to have an effect in prevention. Evidence for reducing melanoma risk from dietary measures is tentative, with some supportive epidemiological evidence, but no clinical trials.
Zinc oxide and titanium oxide are often used in sun screen to provide broad protection from UVA and UVB ranges.
Eating certain foods may decrease the risk of sunburns but this is much less than the protection provided by sunscreen.
A meta-analysis of skin cancer prevention in high risk individuals found evidence that topical application of T4N5 liposome lotion reduced the rate of appearance of basal cell carcinomas in people with xeroderma pigmentosum, and that acitretin taken by mouth may have a skin protective benefit in people following kidney transplant.
Currently, surgical excision is the most common form of treatment for skin cancers. The goal of reconstructive surgery is restoration of normal appearance and function. The choice of technique in reconstruction is dictated by the size and location of the defect. Excision and reconstruction of facial skin cancers is generally more challenging due to presence of highly visible and functional anatomic structures in the face.
When skin defects are small in size, most can be repaired with simple repair where skin edges are approximated and closed with sutures. This will result in a linear scar. If the repair is made along a natural skin fold or wrinkle line, the scar will be hardly visible. Larger defects may require repair with a skin graft, local skin flap, pedicled skin flap, or a microvascular free flap. Skin grafts and local skin flaps are by far more common than the other listed choices.
Skin grafting is patching of a defect with skin that is removed from another site in the body. The skin graft is sutured to the edges of the defect, and a bolster dressing is placed atop the graft for seven to ten days, to immobilize the graft as it heals in place. There are two forms of skin grafting: split thickness and full thickness. In a split thickness skin graft, a shaver is used to shave a layer of skin from the abdomen or thigh. The donor site regenerates skin and heals over a period of two weeks. In a full thickness skin graft, a segment of skin is totally removed and the donor site needs to be sutured closed.
Split thickness grafts can be used to repair larger defects, but the grafts are inferior in their cosmetic appearance. Full thickness skin grafts are more acceptable cosmetically. However, full thickness grafts can only be used for small or moderate sized defects.
Local skin flaps are a method of closing defects with tissue that closely matches the defect in color and quality. Skin from the periphery of the defect site is mobilized and repositioned to fill the deficit. Various forms of local flaps can be designed to minimize disruption to surrounding tissues and maximize cosmetic outcome of the reconstruction. Pedicled skin flaps are a method of transferring skin with an intact blood supply from a nearby region of the body. An example of such reconstruction is a pedicled forehead flap for repair of a large nasal skin defect. Once the flap develops a source of blood supply form its new bed, the vascular pedicle can be detached.
The mortality rate of basal-cell and squamous-cell carcinoma is around 0.3%, causing 2000 deaths per year in the US. In comparison, the mortality rate of melanoma is 15–20% and it causes 6500 deaths per year. Even though it is much less common, malignant melanoma is responsible for 75% of all skin cancer-related deaths.
The survival rate for people with melanoma depends upon when they start treatment. The cure rate is very high when melanoma is detected in early stages, when it can easily be removed surgically. The prognosis is less favorable if the melanoma has spread to other parts of the body. As of 2003 the overall five year cure rate with Mohs' micrographic surgery was around 95 percent for recurrent basal cell carcinoma.
Australia and New Zealand exhibit one of the highest rates of skin cancer incidence in the world, almost four times the rates registered in the United States, the UK and Canada. Around 434,000 people receive treatment for non-melanoma skin cancers and 10,300 are treated for melanoma. Melanoma is the most common type of cancer in people between 15–44 years in both countries. The incidence of skin cancer has been increasing. The incidence of melanoma among Auckland residents of European descent in 1995 was 77.7 cases per 100,000 people per year, and was predicted to increase in the 21st century because of "the effect of local stratospheric ozone depletion and the time lag from sun exposure to melanoma development.