Skin cancer is a malignant growth on the skin which can have many causes. The most common skin cancers are basal cell cancer, squamous cell cancer, and melanoma. 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 is named after the type of skin cell from which it arises. Unlike many other cancers, including those originating in the lung, pancreas, and stomach, only a small minority of those afflicted will actually die of the disease. Skin cancer represents the most commonly diagnosed cancer, surpassing lung, breast, colorectal and prostate cancer. Melanoma is less common than basal cell carcinoma and squamous cell carcinoma, but it is the most serious - for example, in the UK there are 9,500 new cases of melanoma each year, and 2,300 deaths. More people now die of Melanoma in the UK than in Australia. It is the most common cancer in the young population (20 – 39 age group). It is estimated that approximately 85% of cases are caused by too much sun Non-melanoma skin cancers are the most common skin cancers. The majority of these are called Basal Cell Carcinomas. These are usually localised growths caused by excessive cumulative exposure to the sun and do not tend to spread.
Skin cancer is most closely associated with chronic inflammation of the skin. This includes:
Many believe that skin cancer can be prevented altogether by avoiding sunlight entirely, or wearing protective clothing while outdoors. However, studies show that Melanoma Skin Cancer is more common in those who work indoors. Skin Cancer is most common on areas of the body that are not normally exposed to the sun, and then exposing the skin to UV rays excessively.
Skin cancer generally has a 20- to 30-year latency period. Many instances of skin cancer in older individuals today can be traced to behaviours as young adults in the 1970s and early 1980s. Deep tans at that time were routinely spoken of as "healthy." Sunburns represented an inconvenient rite of spring or an awkward preliminary stage in the process of acquiring a "healthy" tan. Severe burns were commonplace. Today we know the approach to be reckless. The incidence rates of skin cancer today in persons over 50 years of age reflect that day's popular ignorance.Top ^
The most common types of skin cancers are:
Basal cell carcinomas (BCC) are the most common. They 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 carcinomas(SCC) 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 SCCs of the lip, ear, and in immunosuppressed patients. Melanomas are the least frequent of the 3 common skin cancers. They frequently metastasize, and are deadly once spread.
Less common skin cancers include: Dermatofibrosarcoma protuberans,Merkel cell carcinoma,Kaposi's sarcoma, keratoacanthoma, spindle cell tumors, sebaceous carcinomas, microcystic adnexal carcinoma, merkel cell carcinoma, Pagets's disease of the breast, atypical fibroxanthoma, leimyosarcoma, and angiosarcoma
The BCC and the SCC often carry a UV-signature mutation indicating that these cancers are caused by UV-B radiation via the direct DNA damage. However the malignant melanoma is predominantly caused by UV-A radiation via the 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.
Many laymen and even professionals consider the basal cell carcinoma (BCC), the squamous cell carcinoma (SCC) and the malignant melanoma as one group - namely skin cancer. This grouping is problematic for two reasons:
Even though it is much less common than BCCs and SCCs, malignant melanoma is responsible for 75% of all skin cancer-related deaths.
While sunscreen has been shown to protect against BCC and SCC it may not protect against malignant melanoma. When sunscreen penetrates into the skin it generates reactive chemicals. It has been found that sunscreen use is correlated with malignant melanoma. The lab-experiments and the epidemiological studies suggests that sunscreen use correlates with melanoma incidence. The question that has to be asked is: "Are sunscreen users also the ones with the highest lifetime exposure to ultraviolet lights?" or are sun screens tumor promoters or carcinogens themselves. Logics might suggest that sunscreen users also are the ones most likely to be burned or have been burned by sun light. If it is true that some suncreen induces the formation of skin cancers, the physical sunscreen which are metallic in nature (zinc and titanium) are likely safer and likely to be inert. In the past, most sunscreens were chemical blockers (benzones, etc.).
There are a variety of different skin cancer symptoms. These include changes in the skin that do not heal, ulcering in the skin, discolored skin, and changes in existing moles. Such as jagged edges to the mole, and enlargement of the mole.
|A modern polarized dermatoscope.|
Clinical diagnosis is made with visual appearance or with the aid of a dermatoscope. The ABCD guideline is helpful for identifying dysplastic nevus and melanoma. Clinical diagnosis can only be confirmed with a skin biopsy. Most skin biopsies are done under local anesthetic with an injection. A shave biopsy is good for diagnosing basal cell carcinoma, while not as well for squamous cell carcinoma. A punch biopsy is preferred for diagnosing squamous cell carcinoma and melanoma over the shave biopsy technique. Excisional biopsy (where the entire lesion is removed down to the deep dermis and subcutanous fat) is the method of choice for diagnosing melanomas. However, for cosmetic reason and practical reasons, a punch biopsy is often used to initially diagnose many large melanomas or melanomas of cosmetically important anatomic locations (nose, face, eyelids, nails, fingers and toes).
Treatment is dependent on type of cancer, location of the cancer, age of the patient, and if the cancer is primary or recurrence. One should look at the specific type of skin cancer (basal cell carcinoma, squamous cell carcinoma, or melanoma) of concern in order to determine the correct treatment required. An example would be a small basal cell cancer on the cheek of a young man, where the treatment with the best cure rate (Mohs surgery) might be indicated. In the case of an elderly frail man with multiple complicating medical problems, a difficult to excise basal cell cancer of the nose might warrant radiation therapy (slightly lower cure rate) or no treatment at all. Topical chemotherapy might be indicated for large superficial basal cell carcinoma for good cosmetic outcome, whereas it might be inadequate for invasive nodular basal cell carcinoma or invasive squamous cell carcinoma.
For low-risk disease, radiation therapy, topical chemotherapy (imiquimod or 5-fluorouracil) and cryotherapy (freezing the cancer off) can provide adequate control of the disease; both, however, may have lower overall cure rates than certain type of surgery. Other modalities of treatment such as photodynamic therapy, topical chemotherapy, electrodessication and curettage can be found in the discussions of basal cell carcinoma and squamous cell carcinoma.
Mohs' micrographic surgery (mohs surgery) is a technique used to remove the cancer with the least amount of surrounding tissue and the edges are checked immediately to see if tumor is found. This provides the opportunity to remove the least amount of tissue and provide the best cosmetically favorable results. This is especially important for areas where excess skin is limited, such as the face. Cure rates are equivalent to wide excision. Special training is required to perform this technique.
In the case of disease that has spread (metastasized), further surgical procedures or chemotherapy may be required.
Scientists have recently been conducting experiments on what they have termed "immune-priming". This therapy is still in its infancy but has been shown to effectively attack foreign threats like viruses and also latch onto and attack skin cancers. More recently researchers have focused their efforts on strengthening the body's own naturally produced "helper T cells" that identify and lock onto cancer cells and help guide the killer cells to the cancer. Researchers infused patients with roughly 5 billion of the helper T cells without any harsh drugs or chemotherapy. This type of treatment if shown to be effective has no side effects and could change the way cancer patients are treated.Top ^
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 via simple repair whereby 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 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.
Although it is impossible to completely eliminate the possibility of skin cancer, the risk of developing such a cancer can be reduced significantly with the following steps:
Although it is generally accepted that UV exposure is the greatest risk factor in melanoma development, some sceptics say no data conclusively proves a link between moderate sun exposure and the likelihood of melanoma.
Australian scientist Ian Frazer who developed a vaccine for cervical cancer, says that a vaccine effective in preventing for certain types of skin cancer has proven effective on animals and could be available within a decade. The vaccine would only be effective against Squamous Cell Carcinoma.
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.