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Understanding the Types of Skin Cancer

Skin cancer is a disease that begins in the cells of the skin. The area of skin with the cancer is called a lesion. There are several types of skin cancer (carcinoma). Melanoma is the most serious. But there are others that are known as nonmelanoma skin cancer. These include:

  • Basal cell carcinoma

  • Squamous cell carcinoma

  • Merkel cell carcinoma

  • Cutaneous T-cell lymphoma

  • Kaposi sarcoma

Basal cell carcinoma and squamous cell carcinoma are more common. The others are not as common.

About your skin

The skin is the largest organ of the body. Skin protects us from heat, sunlight, injury, and infection. It also stores water and fat, and produces vitamin D. The skin has 3layers:

  • The outer layer called the epidermis

  • The middle layer called the dermis

  • The inner layer called the subcutis (subcutaneous)

The epidermis is made of flat cells called squamous cells. Round basal cells are under the squamous cells. The lower part of the epidermis also has pigment-producing cells called melanocytes. These cells darken the skin when exposed to the sun.

The dermis has blood vessels, lymphatic vessels, hair follicles, and glands. Some of these glands make sweat, which helps keep the body cool. Other glands make sebum. Sebum helps keep the skin from getting dry. Sweat and sebum reach the skin's surface through tiny openings called pores.

The subcutis and the lowest part of the dermis form a network of collagen and fat cells. This layer conserves heat and helps protect the body's organs from injury.

Basal cell carcinoma

Basal cell carcinoma, also known as basal cell cancer, is the most common type of skin cancer. It begins in basal cells in the deepest part of the epidermis. It often starts in areas of skin exposed to the sun, such as the face, head, neck, arms, and hands. The cancer lesion often appears as small, raised, shiny, or pearly bumps, but it can have various kinds of appearance. They tend to grow slowly and rarely spread to other parts of the body.

Nearly all basal cell cancers can be treated and cured. In some cases they may come back after treatment. Although this type of cancer rarely spreads to other parts of the body, if not treated it can extend below the skin to the bone. This can cause serious damage to the bone. Having a basal cell carcinoma also puts you at higher risk for other types of skin cancer.

Squamous cell carcinoma

Squamous cell carcinoma, also known as squamous cell cancer, is the second most common type of skin cancer. It begins in flat cells called squamous cells in the upper part of the epidermis. Like basal cell cancer, it often starts in areas of skin exposed to the sun, such as the face, head, neck, arms, and hands. But it can also start in other parts of the body, such as skin in the genital area. Squamous cell carcinoma lesions often appear as a rough or scaly reddish patch on the skin that tends to grow quickly. But it can also have various kinds of appearance.

Squamous cell carcinoma is more likely to grow and spread to other parts of the body than basal cell carcinoma, although it’s still uncommon. Most squamous cell carcinoma is found early enough to be treated and cured.

Merkel cell carcinoma

Merkel cell cancer is a rare type of skin cancer. Merkel cells are types of cells in the upper layer of the skin. The cells are very close to nerve endings, and help the skin sense light touch. Merkel cell cancer occurs when these cells grow out of control. Merkel cell cancer can be dangerous because it tends to grow quickly. It can be hard to treat if it spreads beyond the skin.

Merkel cell cancer tumors are most often found on sun-exposed areas of skin, such as the face, neck, and arms. But they can start anywhere on the body. They usually appear as firm, shiny skin lumps that do not hurt. The lumps may be red, pink, or blue. They tend to grow very quickly.

Cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma is a type of cancer that starts in blood cells called T-lymphocytes. These are white blood cells that are part of your immune system. They normally fight infection in the body. The cancer then affects the skin (cutaneous). It causes scaly patches or bumps called lesions or tumors. The cancer is also known as lymphoma of the skin. It is a type of non-Hodgkin lymphoma.

It is usually a slow-growing cancer. It develops over many years. The two most common types of this cancer are mycosis fungoides and the Sezary syndrome.

Melanoma Introduction

Melanoma is a serious type of skin cancer. It starts in skin cells called melanocytes. Melanocytes are what give skin its color.

There are 3 main types of skin cancer. Basal cell carcinoma and squamous cell carcinoma are more common. Melanoma is a much less common. But melanoma is more likely to spread to other parts of the body. 

About your skin

The skin is the largest organ of the body. Skin protects us from heat, sunlight, injury, and infection. It also stores water and fat, and produces vitamin D. The skin has 3 layers:

  • The outer layer called the epidermis

  • The middle layer called the dermis

  • The inner layer called the subcutis (subcutaneous)

The epidermis is made of flat cells called squamous cells. Round basal cells are under the squamous cells. The lower part of the epidermis also has pigment-producing cells called melanocytes. These cells darken the skin when exposed to the sun.

The dermis has blood vessels, lymphatic vessels, hair follicles, and glands. Some of these glands make sweat, which helps keep the body cool. Other glands make sebum. Sebum helps keep the skin from getting dry. Sweat and sebum reach the skin's surface through tiny openings called pores.

The subcutis and the lowest part of the dermis form a network of collagen and fat cells. This layer conserves heat and helps protect the body's organs from injury.

Where melanoma occurs

Melanoma can occur anywhere on the skin. Men usually get it on the part of the body between the shoulders and the hips called the trunk. They may also get it on their head or neck. Women usually get it on their arms and lower legs. Sometimes, melanoma may occur even on areas of the skin that are never exposed to sunlight. It may even occur in the eye, under a fingernail or toenail, or in the nose and sinuses, or in other parts of the body.

Types of melanoma

Melanoma starts when normal melanocytes become cancerous. When cancer cells are on the skin, the cancer is called cutaneous melanoma. Most of what we know about melanoma (its behavior, staging, and treatment) refers to cutaneous melanoma.

Cutaneous melanomas come in these types:

  • Superficial spreading. This is the most common form, making up about 70% of all cutaneous melanomas. These often grow along the skin for a long time before invading the skin more deeply. They often have irregular shapes and are several shades of brown or other colors, such as black, blue, or red.

  • Nodular. These are often black, dome-shaped lesions. They tend to grow vertically (into deeper skin layers - see below).

  • Acral lentiginous. These are found on the palms of your hands, soles of your feet, under a nail (subungual), or on mucous membranes, such as the mouth, rectum, or vagina (mucosal). This type makes up a larger portion of melanomas in people with naturally darker skin.

  • Lentigo maligna. Common in older people, these lesions are typically flat and large, spreading widely along the surface of the skin. They often begin as benign lesions on the face or other sun-exposed area.

  • Desmoplastic or neurotropic. These melanomas show up as small nodules on the skin, which are nonpigmented (light in color). They can travel and grow along nerves in the skin and can cause the development of fibrous tissue.

  • Amelanotic melanoma. These melanomas are often pink or flesh-colored. They are variants of the more common melanomas because they don’t make pigment. As a result, they can be mistaken for a pimple or other noncancerous growth.

Keeping an eye on moles

Sometimes groups of melanocytes make moles, also called nevi. Most people have some moles on their bodies. These moles are usually pink, tan, or brown. They can be flat or raised, and are usually round or oval. Most moles are on the chest or the upper part of the body.

Moles don't usually grow or change very much. Moles can fade in older adults. Most moles are not cancer (benign), and do not lead to cancer. Some abnormal moles, called dysplastic nevi, are an increased risk of melanoma. These should be checked regularly by a doctor.

How melanoma spreads

If melanoma grows at the site of the original tumor, it tends to grow in 1 of 2 ways:

  • Radial growth. This means the melanoma spreads horizontally along the top layers of your skin. Most melanomas start growing this way, but some may eventually grow into deeper layers of your skin.

  • Vertical growth. This means melanoma grows into deeper layers of skin. This kind of growth is more serious and may spread to other parts of the body. Nodular melanoma grows this way fairly quickly, but most others grow along the top layers of skin first for some time.

If left untreated, melanoma tends to spread to other parts of the body more quickly than most other types of skin cancer, which can make it more dangerous. This spread can be somewhat unpredictable. Melanoma tends to spread first to lymph nodes in the area of your original tumor. For example, if the tumor was on your leg, it may spread to lymph nodes in your groin area. But, sometimes, melanoma may spread to distant areas of your body, such as the liver, lungs, or brain, even if your lymph nodes have not been involved.



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