The term “cancer” refers to a malignant growth of some tissue. Cancers can occur in many types of tissues in the body. Skin cancers are typically a result of malignant growth of the epidermal layer of the skin. These malignant growths in the skin can occur in any region of the body, including areas such as the lips, scalp or skin under the nails. Skin cancers can affect individuals in any age group but are more common in people above the age of 50 years.
Skin cancers can spread rapidly and become lethal. Therefore, any changes in the skin color or presence of a growth on the skin should be taken seriously and examined medically. Some non-cancerous skin conditions such as fungal infections, solar purpura, and warts may also present with skin lesions that are similar to the skin lesions found in case of skin cancers. Therefore, all kinds of skin lesions should be tested by a doctor.
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Causes of Skin Cancer
Skin cancer can occur due to a variety of causes. The following are the main risk factors that increase the likelihood of developing skin cancer:
- Excessive and chronic exposure to ultraviolet radiation from sources such as the sun or UV lamps.
- Repeated exposure to high intensity X-rays.
- A weak immune system (caused by radiotherapy, chemotherapy, or immunosuppression due to drugs or disease such as AIDS).
- Exposure to radium, arsenic, and creosote.
- Having blood relatives with skin cancer.
- Actinic keratosis
- Disorders of skin pigmentation (such as xeroderma pigmentosum, albinism).
- Red or blonde hair, fair skin, freckles, green or blue eyes.
- Presence of unusual moles on the skin.
- Presence of scars on the skin.
Common Types of Skin Cancers
Some types of skin cancers are more common than others in the human population. Melanoma, squamous cell carcinoma, and basal cell carcinoma are the three most common types of skin cancers.
Melanoma is a type of skin cancer that originates in the melanin pigment producing cells of the skin. These cells, known as melanocytes, are located in the outer epidermal layer of the skin. Melanoma can arise either from intact skin or a mole in the skin. The cancerous growth in melanoma can be a flat or raised growth that is brown or black in color. Some parts of this outgrowth can be white, red or blue in color.
The outgrowth in melanoma can appear anywhere on the skin. In women, they commonly occur on the legs and back. In men, they commonly arise on the trunk. The growth of the skin lesions in melanoma can either be slow or rapid. For example, lentigo maligna melanoma and superficially spreading melanoma grow very slowly. In contrast, nodular melanoma grows very fast, and frequently leads to ulceration and bleeding.
The cancerous cells may also spread to other parts of the body through blood or lymph. Surgical removal of the skin lesions is the usual treatment for melanoma.
Squamous cell carcinoma
Stratum corneum is the uppermost layer of the epidermis. Abnormal growth of squamous cells present in the stratum corneum causes squamous cell carcinoma. The skin lesions in squamous cell carcinoma appear as fleshy nodules that are dome-shaped, scaly, and red in color.
The central regions of these nodules may contain ulcers. These nodules typically appear in skin areas that are exposed to the sun. Squamous cell carcinoma is a slow growing skin cancer. However, it can spread to other organs of the body. Treatment of squamous cell carcinoma also includes surgical removal of the skin lesions.
Basal cell carcinoma
Basal cell carcinoma is a slow growing skin cancer that arises from the basal cells in the lowermost layer of the epidermis (also known as stratum basale). This type of skin cancer is typically localized to the skin, and rarely spreads to other tissues. The skin lesions in basal cell carcinoma are in the form of pearl-shaped greyish nodules. These nodules typically occur on skin areas that are exposed to sunlight, such as neck, scalp, lips, face, upper back and upper chest.
These nodules may also have ulcers that ooze out fluid. Due to its localized nature, basal cell carcinoma is rarely lethal. Treatment options for basal cell carcinoma include chemotherapy, radiotherapy, and surgery. Small lesions may also be removed via laser, electrocautery, or freezing.
Rare Types of Skin Cancers
There are many kinds of skin cancers that are relatively rare. Some of these are mentioned below.
Kaposi’s sarcoma is a rare type of skin cancer that is characterized by the appearance of brown, purple or red nodules on the skin. These skin lesions arise from cells present in the lymphatic vessels or blood vessels. Kaposi’s sarcoma is caused by HHV-8 virus. This condition is frequently associated with AIDS, organ transplants, and heritage from equatorial Africa and Mediterranean regions.
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Angiosarcoma is a type of aggressive tumor that arises from blood vessels in the skin (usually on the scalp region).
Merkel cell carcinoma
This type of skin cancer arises from the Merkel cells present in the skin. The Merkel cells are neuroendocrine cells. The skin lesions in Merkel cell carcinoma arise as violet or red bumps in areas of the skin that are exposed to the sun.
Sebaceous gland carcinoma
Sebaceous gland carcinoma is a rapidly spreading type of skin cancer that usually appears on the eyelids. This type of skin cancer is usually seen in the elderly.
Paget’s disease of the breast
This type of skin cancer usually occurs in conjunction with breast cancer in women. The area of the skin around the nipples becomes red and scaly.
Anogenital carcinoma is characterized by the appearance of wart-like lesions on the scrotum, penis, anus, vulva, and perianal regions.
Precancerous and Non-Cancerous Growths on the Skin
Precancerous lesions are changes that may develop into cancer after some time. Actinic cheilitis and actinic keratosis are two types of precancerous growths that affect the skin.
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Not all abnormal growths on the skin are cancerous or precancerous lesions. Examples of non-cancerous growths on the skin include birthmarks, moles, skin tags, genital or anal warts, and molluscum contagiosum.