What is skin cancer?

Skin is the largest and heaviest organ in human body. It is responsible for essential functions including protection against environmental hazard, metabolism, electrolyte balance, body temperature and even body circulation control. While it is amazingly efficient it is also quite vulnerable as well.

Same as all other organs and tissues, skin cells can turn malignant during the life time. This marvellous organ is composed of different cells with different roles and function. Consequently we should expect various and different types of cancer based on the cells involved. Prevalence of each cancer varies from very common such as Basal Cell Carcinoma, to those that are less prevalent such as Merkel carcinoma. Common forms of skin cancers are divided into Melanoma skin cancer and Non-Melanoma skin cancers that are discussed further below.

Skin cancers are unique among other cancers with two special features. Firstly some skin cancers like Melanoma and Merkel cell tumour can invade and spread through blood vessels or to other remote organs while they are still very small in size and in proportion to normal cells. For example colorectal cancers generally must reaches to a size of few centimetres to be capable of metastasize to other organs. Melanoma however can metastasize even when as small as 0.5mm, making them extremely aggressive and fatal.

Secondly, against all other organs they are exposed and visible giving us greater opportunity of early detection. Despite a greater increase in skin cancer incidence in the past 30 years, improvements in early detection has deceased the mortality rate of skin cancers.

Types of skin cancer

Three types of skin cancer compromising the majority of patients with skin malignancies:
1- Basal Cell Carcinoma (BCC)
2- Squamous Cell Carcinoma (SCC)
3- Malignant Melanoma

Basal Cell Carcinoma (BCC):
Also called rodent ulcer is the most common type of skin cancers. These cancers rarely spread to other distant organs, they can however involve and destroy the surrounding tissues ending up to disfiguration, severe pain secondary to nerves invaded by the tumour, and if close to bones or muscles e.g. face ,nose, ears, around the eyes, can cause disabilities.
There are few subtypes of BCC:
- Superficial Multifocal BCC
They present as a red, well-circumscribed patch or plaque, often with a whitish scale. They easily mimic dermatitis or other skin conditions like psoriasis.

Superficial BCC (image from Medscape)

- Infiltrative
This type may look like superficial but has invaded the deep structures of skin.

Infiltrative BCC-back of one of clinic patients and a closer view. This lesion incidentally noticed when patient was being checked for chest infection.

Same lesion under dermatoscope

- Nodular BCC
Nodular basal cell carcinoma is the most common type of basal cell carcinoma and usually presents as a round, pearly, flesh-colored papule. They bleed easily and may look ulcerated. The most common area is the face.

Nodular BCC

Another case of nodular BCC. The white area around the cancer is due to inappropriate cryotherapy (Freezing) done somewhere else and is not a feature of cancer.

-Morphaeic BCC
Such lesions appear as flat or slightly depressed, scar-like, and firm. The tumor appears as a white or yellow, waxy, sclerotic plaque that rarely ulcerates. The morpheaform (sclerosing) type of basal cell carcinoma is often the most difficult type to diagnose, as it bears little resemblance to the typical nodular BCC.

Morphaeic BCC-image from Medscape

Squamous Cell Carcinoma (SCC):
This cancer is due to malignant growth of the cells called Squamous cells ( i.e. resembling a scale or scales). These cells are responsible for physical protection of body surfaces that are in direct contact with environmental hazards. Chronic exposure to physical or chemical irritants causes rapid replication of these cells ending up in malignant cells to grow. The most famous cancers originating from squamous cells are lung cancer ( due to chemicals in tobacco ), Oesophagus cancer ( chronic acid exposure ), genital and cervical cancer ( mainly due to a virus called HPV) and skin ( mostly as a consequence of UV exposure). These malignant cells are highly invasive if grow enough to reach the blood or lymphatic vessels facilitating them spread to other organs like brain, lungs and liver.
On the skin they can present as a red slightly scaly patch flat or raised, firm and sometimes tender papules. This cancer can spread and metastasize to distant organs e.g. Brain, liver…etc. Metastasis is especially more common in high risk areas like ears, lips, scalp and to a lesser extent other areas of head and neck.

SCC on the lower lips on both right and left side

A very common form of early SCC called Bowen's and represents just as a red patch

Another Bowen's skin cancer (SCC in-situ)

Raised SCC - image from Webmed

SCC may just look like a dry skin lesion. When red and tender it’s a sign of malignancy
however it’s not always present causing patient ignoring them.
(image from skincancerphysician.blogspot)

SCC may just look like a dry spot and easily missed. Ears are one the high risk areas that SCC can metastasize quickly.

Melanoma is highly invasive being capable of spreading in body even when as small as 1-2mm. The origin of this cancer are the cells producing skin’s pigment and are called Melanocytes. It is interesting to know that the number of these cells in different races with various skin colours are the same and a darker skin is just due to more pigment (Melanin) production by these cells. Moles are formed by increased number of these cells in parts of skin.Melanoma is the name given when the melanocytes within a mole turn malignant.
Melanoma is rare in children but is the first cause of cancer related death in youngsters 16-30 years of age. It is considered the third most common cancer in elderly after colorectal cancers ( in both sexes) , breast and prostate cancer in females and males respectively.
The general social conception a malignant mole/Melanoma is a very dark to black, ugly and large mole happening merely in those love to tan or are severely exposed to sun. This is however only partly true. Very similar to the benign moles, melanoma may have various colours and shapes. Therefore, melanoma is a big mascaraed and can mimic a small light or dark brown mole or a freckle. They can even look completely colourless and pink.Chronic sun exposure and history of other skin cancers increases the possibility of Melanoma. It is however important to notice that Melanoma can happen in everyone regardless of sun exposure history and in areas that can hardly been exposed e.g. buttocks ,genitalia, between the toes , soles , scalp and even inside of the eyes.The most common risk factors in developing Melanoma are:

1- Fair skin, blue eyes and red hairs
2- Family history of melanoma
3- Frequent moles. The more, the higher
4- Previous Melanoma (increases the risk by 10 fold)
5- Previous other types of skin cancers like BCC or SCC (x3 fold)
6- Dysplastic Nevus Syndrome (DNS). This is a very important risk factor and 20% to 50% of these will end up in Melanoma in their life time.

DNS is diagnosed if any 2 of these conditions exists:
A) Having above 100 moles ( 50 if younger than 20 or older than 50 years of age)
B) More than 2 atypical/Dysplastic moles. Diagnosis of atypical mole is generally made by physician based on the size, irregularity of border, various shades of colour mainly checked with dermatoscope. A mole above 5mm is also considered atypical.
C) One or more mole on buttocks
D) 2 or more moles on feet (excluding soles)

What is DYSPLASTIC mole?
Dysplastic (atypical moles) are unusual benign moles that may resemble melanoma. People who have them are at increased risk of developing single or multiple melanomas. The higher the number of these moles someone has, the higher the risk; those who have 10 or more have 12 times the risk of developing melanoma compared to the general population. Dysplastic nevi are found significantly more often in melanoma patients than in the general population.
Medical reports indicate that about 2 to 8 percent of the Caucasian population have these moles. Heredity appears to play a part in their formation. Those who have dysplastic nevi plus a family history of melanoma have an extremely high risk of developing melanoma. Individuals who have dysplastic nevi, but no family history of melanoma, still face a 7 to 27 times higher risk of developing melanoma compared to the general population-certainly a great enough risk to warrant monthly self-examination, regular professional skin exams and daily sun protection.

Dysplastic Nevus Syndrome

With regards to diagnosis of Melanoma see Mole check / Mole Scan
The most determining factor in prognosis is depth of of the tumor with the best when below 0.4 mm followed by thickness less than 1 mm.
There are 5 basic types of Melanoma that each one can begin in situ _meaning they occupy only the top layers of the skin _ and progress to invasive. Invasive melanomas are more serious as the have penetrated deeper into the skin and may spread to other areas of the body.
Superficial spreading melanoma is by far the most common type, accounting for about 70 percent of all cases. This is the one most often seen in young people. As the name suggests, this melanoma grows along the top layer of the skin for a fairly long time before penetrating more deeply.
The first sign is the appearance of a flat or slightly raised discolored patch that has irregular borders and is somewhat asymmetrical in form. The color varies, and you may see areas of tan, brown, black, red, blue or white. This type of melanoma can occur in a previously benign mole. The melanoma can be found almost anywhere on the body, but is most likely to occur on the trunk in men, the legs in women, and the upper back in both.
Albeit Irregular border or color variation is the main clinical signs of melanoma, most of early melanomas don't look outstanding and detection is only possible with skilled physician.

Superficial spreading melanoma on right arm. Asymmetry, irregular border and various shades of colors are typical

Superficial spreading melanoma on the left arm of another patient. This mole doesn't look typical. That was discovered in a routine skin check. The only way of diagnosis is dermoscopic examination which shows small peripheral dots in the top and regression in the middle.

This lesion on back of the ear detected in a routine skin check It is not only in an area that is note visible by the patient, also mimics an insignificant tiny freckle. Again only dermoscopic examination could show regression as a sign of melanoma in situ.

Lentigo maligna is similar to the superficial spreading type, as it also remains close to the skin surface for quite a while, and usually appears as a flat or mildly elevated mottled tan, brown or dark brown discoloration. Since they grow slowly and appear as a pigmented patch, they are mostly mistaken by patients and even their doctor as a simple freckle or a patch of sun damaged skin. This type of in situ melanoma is found most often in the elderly, arising on chronically sun-exposed, damaged skin on the face, ears, arms and upper trunk. When this cancer becomes invasive, it is referred to as lentigo maligna melanoma.

Lentigo Maligna on the nose. Courtesy of Dr Ian McColl, from skin cancer college of Australia

Lentigo Maligna on forearm. Courtesy of Dr Ian McColl, from skin cancer college of Australia

Acral lentiginous melanoma also spreads superficially before penetrating more deeply. It is quite different from the others, though, as it usually appears as a black or brown discoloration under the nails or on the soles of the feet or palms of the hands. This type of melanoma is sometimes found on dark-skinned people, and can often advance more quickly than superficial spreading melanoma and lentigo maligna. It is the most common melanoma in African-Americans and Asians, and the least common among Caucasians.

Nodular melanoma is usually invasive at the time it is first diagnosed. The malignancy is recognized when it becomes a bump. It is usually black, but occasionally is blue, gray, white, brown, tan, red or skin tone. The most frequent locations are the trunk, legs, and arms, mainly of elderly people, as well as the scalp in men. This is the most aggressive of the melanomas, and is found in 10 to 15 precents of cases.

Amelanotic Melanoma can be completely colourless looking pink or skin coloured. These mimic benign skin lesions like dermatitis or even insect bites!

Amelanotic Melanoma on back. The patient was unaware of the lesion that was confirmed as invasive melanoma

Less common Skin cancers:
There are other types of skin cancers that are not such common. These may originate from the various types of cells consisting skin like sweat glands, hair follicles, fibroblasts (Collagen producing cells) etc. Among all Merkel cell Tumour is the most invasive one with a very high risk of local recurrence or distant metastasis. It presents as a red papule mostly in head and neck of men.
Again early diagnosis is critical and treatment requires multi-speciality team.

Merkel cell tumor, courtesy of Dr Con Pappas from Skin Cancer College of Australia

Treatment for skin cancer

Almost all skin cancers can be treated successfully if diagnosed and treated early. However if not treated, skin cancer can be fatal.
No skin cancer should be neglected. The earlier any skin cancer is diagnosed, the less invasive and more successful any treatment is likely to be.
Given various types of skin cancer and different stages a cancer can be, there are different treatments available. Treatment can vary from simple local medication to extended surgeries and chemotherapy. Treatment should therefore be tailored individually.

In choosing the best treatment option, your doctor will consider:
The type of skin cancer
The size of skin cancer
Location of the skin cancer
Whether the skin cancer has spread to other organs within the body.

Cancer council knows the following options acceptable treatments for skin cancer:
Surgical removal (excision) of the tumour and surrounding tissue.
Curettage (scraping and burning).
Cryotherapy with liquid nitrogen (commonly referred to as "freezing").
Radiotherapy (use of high energy rays such as X-rays to destroy cancer cells within a specific area).
MOHS is highly specialised surgery in which the cancer (generally NMSC only) is removed little by little and checked under the microscope immediately.
Photodynamic therapy - uses a light source and special cream to destroy cancer cells.
Imiquimod - a cream that destroys skin cancer by stimulating the body's immune system to fight the cancer.
Chemotherapy is treatment with drugs, either pills or injections. It may be used to treat melanoma that has spread to other parts of the body.