According to the World Health Organization, WHO, skin cancer ranks as the fifth most commonly occurring cancer in the world. In fact, in the United States alone, more than 9,500 people are diagnosed with skin cancer daily; Making it the most common form of cancer in the United States (even more common than breast cancer). This cancer which develops simply by uncontrolled proliferation of skin cells can become so dangerous that about 2 patients die of the disease every hour; However, skin cancer is far from a death sentence. Research shows that when detected early, a melanoma (the deadliest form of skin cancer) actually has a 99% five-year survival rate for patients. It is therefore crucial that you understand what skin cancer is, how to identify skin cancer, treatment options available for patients with skin cancer, and what you should do to make yourself less likely to get skin cancer. But first, it is advisable that you understand what the skin is and how it works.
Melanoma
Anatomy of the skin
Table of Contents
The skin is the largest organ found in the body. This organ forms a lining over the entire body. It serves as a protective shield, helps inform the brain of the nature of the body’s environment through signals picked up by receptors it houses, and regulates various functions like temperature and water loss. Due to the level of exposure of the skin to the external environment, this organ is usually the first to receive any assault. These assaults could be microbial, chemical, or electromagnetic.
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The skin is arranged in layers and is made up of several types of cells. These cells include:
- The melanocytes (cells involved in melanin production)
- Squamous or flat cells (found in the middle and outer layers of the skin). Due to their location, the squamous cells are continually shed and are replaced by continuously dividing basal cells.
- Basal cells (cells situated in the deepest layers of the skin), and
- Non-melanocytes (generally, cells that do not produce melanin are tagged as non-melanocytes). These cells may be located in the outer or inner layers of the skin. These cells include Langerhans cells, keratinocytes, and Merkel’s cells.
Usually, skin cancers are named based on their cellular origin.
Epidemiology of skin cancers
Skin cancers are the most common form of cancer in light-skinned individuals. According to the American Cancer Society ACS, in 2020, about 19.3 million new skin cancer cases were recorded worldwide. This number continues to grow every year.
In fact, approximately 1 in 5 Americans develop skin cancer before they die, and about 48 Americans die of skin cancer every day. Due to reasons such as the increased exposure to sunlight, reduced protection against sunlight, and lower estrogen levels, the American Academy of Dermatology theorizes that men are at a higher risk of developing skin cancers than women.
Causes of skin cancer
Skin cancers develop as a result of damage to the DNA which causes the skin cells to rapidly divide and resist every growth-inhibiting signal. Various factors may cause damage to the DNA; however, the most common factor which damages the skin cells’ DNA is exposure to Ultraviolet light.
Usually, the body has an intrinsic mechanism involving genes such as the p53 gene that repairs damaged DNA or destroys cells with damaged DNA; however, due to continuous exposure, the mutations caused by the Ultraviolet rays accumulate. When this happens, the mutations overwhelm the repair mechanisms and even favor the development of features also known as hallmarks that allow the cancerous cells to thrive.
When cancer cells thrive, they form disorganized masses and continue to divide uncontrollably.
Types of skin cancer
The type of skin cancer a person gets is determined by the initial skin cells affected by the mutation. For instance, a skin cancer that begins from basal skin cells is called a basal cell carcinoma while cancer that begins in squamous skin cells is known as squamous cell carcinoma.
Majorly, there are 3 types of skin cancer They are:
Basal cell carcinoma (BCC): This is the most common form of skin cancer. It develops from the basal cells of the skin.
Squamous cell carcinoma (SCC): This is the second most common form of skin cancer. As the name implies, the SCC is cancer that develops from the squamous cells found in the outer layers of the skin.
Melanoma: Melanoma is a relatively rare form of skin cancer that develops from the melanocytes. Because of its high propensity to spread, this cancer is often referred to as the most serious form of skin cancer.
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Other types of skin cancer include
Cutaneous T-cell lymphoma: This is a very rare form of blood cancer. It begins in a type of white blood cells found in the skin known as the T cells. These cells are very abundant in the skin. In fact, about 20 billion T-cells are found in the skin (this is about twice the total number of T cells found in the entire body). Mycosis fungoides and Sézary syndrome are the two types of cutaneous T-cell lymphoma.
Dermatofibrosarcoma protuberans (DFSP): This is a rare skin cancer that begins in the middle layer of the skin, the dermis. This cancer tends to grow slowly. It rarely spreads to other parts of the body. It also has a high survival rate.
Usually, the first sign of this skin cancer is often a small bump on the skin. This bump is almost similar to a deep-seated pimple or rough patch of skin. DFSP may also look like a scar. In children, it may remind you of a birthmark
Merkel cell carcinoma: This is a rare skin cancer that begins in the Merkel cells found in the skin. The condition is often tagged “aggressive” because unlike DFDP, it often spreads to other parts of the body and has a very high likelihood of returning even after treatment.
Sebaceous carcinoma: This is a rare form of skin cancer that develops from the sebaceous glands. This condition however most commonly develops from sebaceous glands in and around the eyes due to the increased density of sebaceous glands in those areas.
Risk factors
A risk factor is anything that increases the odds of getting a disease such as cancer. These risk factors do not mean that once you have them, you will definitely develop skin cancer, however, it only means that these factors have been associated with skin cancers and it’s advisable that you avoid them. Risk factors help you watch out for diseases associated with these factors so that you can always detect them early. This early detection helps the prognosis of the disease.
There are several risk factors that predispose you to develop skin cancer. While some risk factors such as exposure to sunlight can be changed, others like your family history and genes can’t.
Here are some risk factors for skin cancer:
- Fair skin
The risk of getting skin cancer is much higher for whites and people with fair skin than for African Americans. This increased risk is due to the fewer number of melanin pigments (a pigment produced by melanocytes which protect the skin from ultraviolet light from the sun) in fair-skinned people than those with dark skins.
For this same reason, albinos are also at an increased risk of developing skin cancer.
- Light-colored eyes, red or blonde hair
Having light-colored eyes, such as blue, green, grey, or amber eyes is typically associated with having a low melanin pigment in the skin. Additionally, red and blonde hairs also denote a low concentration of melanin in your skin.
People with these features are more susceptible to damage from the ultraviolet rays of the skin and prone to developing skin cancers.
- Certain types and increased number of moles
A mole (also known as a nevus) is a benign (non-cancerous) pigmented tumor. Moles are not usually found in infants; they often begin to appear in children and young adults.
The common moles, also known as the common nevi, are usually not a problem. In fact, you can actually have about 10 to 40 moles by adulthood. However, some other types of moles have been associated with skin cancer patients. The risk of developing this cancer increases with the number of moles the individual possesses.
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There are different types of moles that increase the risk of getting skin cancer. These include:
Atypical moles (dysplastic nevi): These moles can be deceptive. In that they actually look a lot like the common moles, however, they also have some features of melanoma. Atypical moles are somewhat larger than moles (somewhat larger than a pencil eraser) and have abnormal shapes or colours. Atypical moles tend to have uneven colours with dark brown centres and lighter, uneven edges. Like the common moles, dysplastic nevi usually develop in parts of the skin exposed to sunlight, such as the face; However, unlike the common moles, these moles can also appear in places such as the breasts, waist, and buttocks which have a low degree of exposure to sunlight.
Dysplastic nevi are often inherited. Although most dysplastic nevi do not develop in melanoma, a small percentage of these moles may over time become cancerous.
Due to the probability of dysplastic nevi becoming cancerous, people with an increased number of atypical moles are at a higher risk of developing skin cancer. People with a higher number of dysplastic nevi are said to have dysplastic nevus syndrome or familial atypical multiple mole and melanoma syndromes, FAMMM.
Due to the increased risk of melanoma, people with this syndrome need very thorough and regular skin exams by a dermatologist (a doctor who specializes in the skin and its associated problems). Sometimes, your doctor may request full-body photos to help him/her identify any moles present and observe the progression of these moles. This allows early detection of skin cancer and allows the physician to take appropriate steps to treat the condition.
In addition, many doctors recommend that these patients be taught to do monthly skin self-exams.
Congenital melanocytic nevi: Moles present right from birth are called congenital melanocytic nevi. Depending on the size of the nevus, the lifetime risk of this type of mole developing into a melanoma is estimated to be between 0% and 5%.
Also, people with larger congenital nevi have a higher risk of developing melanoma than those with smaller nevi. For instance, congenital nevi smaller than the size of the palm of the hand is less likely to develop into a melanoma compared to nevi that cover large portions of the buttocks and back.
- Family history of skin cancer
Your risk of melanoma is higher if one or more of your first-degree relatives (parents, brothers, sisters, or children) has had melanoma. Around 10% of all people with melanoma have a family history of the disease.
The increased risk might be because of a shared family lifestyle of frequent sun exposure, a family tendency to have fair skin, certain gene changes (mutations) that run in a family, or a combination of these factors.
- Personal history of skin cancer
Generally, a person who has already had skin cancer has a higher risk of developing another. Also, people who have had other types of skin cancer such as squamous cell, or basal cell carcinomas are also at risk of developing a different form of skin cancer like melanoma.
- Having a weakened immune system
Generally, the immune system is involved in defending the normal body cells from damage including those from cancerous cells. People with a weakened immune system following disease or medical treatments are at a greater risk of developing skin cancers.
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For example, in a publication by Danish researchers in the Journal of the American Academy of Dermatologists, the scientists observed that the incidence of Basal cell carcinoma was 2.43 per 1000 person-years in people who are HIV positive compared to 1.43 per 1000 person-years among people who are HIV negative. We know that HIV greatly suppresses and destroys the immune system, leaving it weak to fight other diseases including skin cancers.
Also, a higher incidence of skin cancers has been observed in people who get organ transplants as these people are usually given medicine that helps weaken their immune system. This immunosuppressive therapy reduces the chances of their body rejecting the new organ but also increases the chances of them developing some other diseases including skin cancers.
- Old age
Older people are at a higher risk of developing skin cancer than those who are young. This increased risk is due to the reduced ability of the old skin to carry out the usual protective functions of the skin.
- Being male
Males are more prone to developing skin cancers.
- Xeroderma pigmentosum
Xeroderma pigmentosum is a rare inherited condition that increases the susceptibility of the DNA to damage from UV rays. People who have this condition are at a higher risk of developing skin cancer as even a small amount of exposure to sunlight may trigger skin cancer.
- Exposure to ultraviolet (UV) light
Increased exposure to UV light is actually the most important and general risk factor for developing skin cancers. Most skin cancers are precipitated after exposure to the damaging UV rays from the sun.
Symptoms of skin cancer
Generally, skin cancers are usually expressive with features such as the appearance of lumps or growths on the skin. The size, color, shape, and distribution of the lump vary based on the type of skin cancer. Also, the associated pain and discharge from the lump are variable.
Metastasis of skin cancer
Metastasis of skin cancer describes the path cancerous skin cells follow during spread.
Basal cell carcinoma and squamous cell carcinoma rarely metastasize however, the melanoma is often metastatic. It may spread to other sites including the bones, cartilages, and distant organs such as the liver and brain via routes such as lymph or blood.
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Diagnosis of skin cancer
A good diagnosis of skin cancer begins with a thorough history taking. Here your dermatologist will ask you about your health, past medications, and the symptoms you complain of.
Your dermatologist will then proceed to perform a careful physical examination and check for lumps and growths.
If your dermatologist finds a spot or lump on your skin that may be an indication of skin cancer, your dermatologist first anesthetizes that area and then removes all or part of it.
This process is called a skin biopsy. It is actually a simple and safe procedure.
Your dermatologist will then observe the tissue collected. The type of cell visualized determines the type of cancer that may be present.
Your dermatologist will proceed to make a report of the findings and then inform you.
Other tests such as sentinel lymph node biopsy and lymph node dissection may be required to get a proper diagnosis.
After your doctor has determined the type of cancer, he/she may need to stage cancer to get the most appropriate treatment option.
Staging of skin cancer
Staging cancer is the process of determining where cancer has spread and how far it has actually spread. The staging of skin cancers depends on the type of skin cancer. However, generally, skin cancers can be divided into 4 stages
Stage 0: At this stage, the cancer is still small and is localized to the epidermis of the skin. A basal cell carcinoma is less than 2cm large at this point.
Stage 1: At this stage, cancer may have invaded the dermis; however, it has not invaded the muscle, cartilage, bone, lymph nodes, or other organs.
Stage 2: Like the stage 1 skin cancer, cancerous cells in stage 2 may have also invaded the dermis but have not invaded the muscle, cartilage, etc. However, the cancer is relatively larger.
Stage 3: Cancer has spread to areas beneath the skin, such as into muscle, bone, cartilage, or lymph nodes, however, these sites are actually close to the original tumor.
Stage 4: Cancer can be any size and may have spread to nearby lymph nodes. It has also spread to areas outside the skin, such as to distant organs like the brain or lungs, or has invaded the skeleton (axial or appendicular).
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Prognosis of skin cancer
The prognosis of skin cancer depends on the stage and the type of skin cancer.
- Basal cell carcinoma
When detected early, BCC has an excellent prognosis, with a 100% survival rate for cases that have not spread to other sites. Typically, BCCs tend to grow slowly and are locally destructive. When treatment is delayed, BCC can become difficult to manage, even resulting in loss of nerve function and visual impairments for tumors around the orbits.
- Squamous cell carcinoma
When detected early, an SCC has a relatively good survival rate. The overall 5-year survival rate for patients who present early with the condition is greater than 90%. This high survival rate decreases to about 25%-45% if this cancer is left untreated and allowed to metastasize to surrounding lymph nodes.
- Melanomas
According to SEER data from 2011-2017, these are the 5-year relative survival rates of melanomas:
Those localized to primary sites have a 99.4% survival rate; Those characterized by regional spread to regional lymph nodes have a 68.0% survival rate while melanoma with distant metastasis has a 29.8% survival rate. This reiterates the importance of early detection of skin cancer.
The prognosis of skin cancer largely influences the nature of the treatment given.
Treatment of skin cancer
Due to advancing technology, skin cancers can be treated effectively with several precise methods most of which guarantee maximum success. These include:
1. Surgery: This is the definitive treatment for early-stage cancers. Some surgeries such as the Curettage and Electrosurgery, Mohs surgery, and cryosurgery are minimally invasive while others like the wide local excision and skin grafting are quite invasive surgical options.
2. Adjuvant therapy: This is an additional therapy given to support and increase the effectiveness of the primary therapy. This therapy may be chemical or radiation. For instance, radiation therapy is used as adjuvant therapy in SCC while imiquimod and fluorouracil have been observed to yield good results when used in BCC < 2cm large.
3. Radiation therapy: It may also be used as a primary treatment. This is often seen in patients who are not surgical candidates. However, this sort of treatment is contraindicated in patients who have genetic conditions that predispose their cells to skin cancer if treated with radiation.
4. Chemotherapy: Certain deadly skin cancers such as stage 4 melanomas have been treated with certain chemicals and have yielded good results. Dacarbazine for instance was the first drug approved by the FDA after it had a 22% success rate in stage 4 treating melanomas. Other newer drugs include carboplatin and paclitaxel and Interleukin 2.
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Prevention
Here are a few tips that could help you reduce your chances of getting skin cancer.
- Seek shade from intense sunlight.
- Avoid getting sunburned.
- Do not use UV tanning beds.
- Ensure you cover yourself with densely woven clothes. These clothes offer greater protection against the sun’s UV light compared to lighter ones. You can check the level of protection of cloth from sunlight by holding it up to the light and checking if you can see through. A good fabric should not allow you to see through.
- Examine your skin regularly
- See a dermatologist at least once a year.
Conclusion
The incidence of skin cancer continues to rise every year, however, this cancer, though seemingly deadly, may simply be avoided and effectively treated when we are armed with the knowledge of what it is and how to detect and easily manage it.
References
HIV may increase the risk of skin cancer | aidsmap
Skin cancer types: Sebaceous carcinoma overview (aad.org)
The Sun Keeps Rising: Why Seniors Can’t Skip UV Protection – The Skin Cancer Foundation
Skin cancer – Symptoms and causes – Mayo Clinic
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