Skin Cancer – Causes, Treatment and Overview

Skin Cancer

‘Skin Cancer’, one of the most common types of cancer, is caused by uncontrolled growth of epidermal (external layer of the skin) cells, mostly due to the sun exposure. The unrepaired damage to the DNA (Deoxyribonucleic Acid) induces mutations resulting into rapid and abnormal multiplication of the skin cells to form either Benign (non-cancerous) or Malignant (cancerous) tumours. Benign tumours do not spread, while Malignant tumours pervade and damage the growth of normal tissues. Cancerous cells have a tendency to get detached from the tumour and spread though the bloodstream or lymphatic vessels to form additional tumours in other body parts. Skin cancer can affect individuals of all races and colours, though it is more prevalent in fainter skins, that tends to get sun-damaged easily.

The skin is made of different cells, most of which are continually motile. The rounded ‘Basal cells’ beneath the skin surface tend to flatten as they produce new cells and replace the dead flaky ‘Squamous cells’ on the skin surface. ‘Melanocytes’, the melanin-producing cells, the pigment that helps to guard the skin from harmful Ultra-violet (UV) radiations of the sun. ‘Merkel cells’ (Merkel-Ranvier cells/Tactile Epithelial cells) are oval-shaped cells, that act as mechano-receptors giving the skin its ability for sensation to touch. When any of these cells get damaged, they may progress into Skin Cancer.

All types of Skin cancers are serious and require prompt attention. However, types of skin cancer, diagnosis and treatment methods vary depending upon the type of skin cells affected.

The various Skin cancer types are elaborated below:

Basal Cell Carcinoma (BCC):

BCC is one of the commonly occurring skin cancers and can affect any part of the body. Though, it tends to be more prevalent on the sun-exposed body areas such as head, neck, face and ears. It occurs when one of the basal cells develops a mutated DNA. The basal cell DNA controls the generation of new cells, and it signals the instructions accordingly to the cell. However, the mutated DNA sends unusual signals that results into rapid multiplication and abnormal growth of basal cells.

BCC tends to grows gradually and it is rare for them to spread or metastasize from the actual site of tumour. But, if untreated for long can grow wide and skin deep, damaging the tissues, skin and bone. In many severe and aggressive cases of BCC, it can spread to the distant areas of the body. BCC also tends to re-occur at the original cancer site and patients who suffered from BCC once are at a potential risk of acquiring a new one gain. Almost, fifty percent of BCC sufferers may develop a new cancer again within 5 years of their first prognosis.

Squamous Cell Carcinoma (SCC):

SCC is the second most common form of cancer that results into uncontrolled and abnormal growth of squamous cells. SCC develops in the squamous cells that make up the middle and external layers of the skin. These cells are present in many areas of the body and the cancer can develop in any of those places where the squamous cells are present. More specifically, SCC of the skin refers to the cancer that occurs in the squamous cells of the epidermis. It is caused as a result of abnormal modification in the squamous cell DNA.

The damage and modification in the DNA can occur due to exposure to harmful UV rays of the sun or other external agents, that could induce abnormalities to the squamous cells by damaging them. Like BCC, SCC also tends to develop on the areas that are open to sun exposure, however can develop on other body areas too. If undiagnosed and untreated for prolonged period, can get enlarged and travel to other body parts causing severe complications.

Melanoma:

This type of skin cancer develops when the pigment producing cells (Melanocytes) mutate and grow uncontrollably. Melanocytes produce the pigment that gives colour to the skin known as ‘Melanin’. The pigment Melanin is classified into 2 types: Eumelanin and Pheomelanin. As the skin gets exposed to the UV radiations, the Melanocytes are triggered to produce more melanin. However, only the Eumelanin pigment is able to safeguard the skin by tanning or darkening it.

Melanoma cancer develops when the DNA in the melanocytes gets damaged due to excessive tanning/burning caused by UV exposure. Thus, the mutated DNA causes rapid, abnormal cell growth. This cancer tends to develop on the sun-exposed body parts; however, it can spread to other regions of the body. Melanoma is quite a rare phenomenon in darker skins. As dark-skinned individuals naturally have more Eumelanin and fair-skins have more Pheomelanin. Eumelanin has the ability to safeguard the skin from harmful UV damage, while, Pheomelanin lacks it. Thus, fair-skins are more susceptible to Melanoma, than dark-skinned individuals.

Melanoma is a more severe type of skin cancer, than BCC and SCC, due its ability to spread and affect other organs if not taken care of at an initial stage. If the cancer has spread skin deep or to the other organs, it can be incurable and deadly.

Merkel Cell Carcinoma (MCC):

MCC, also called as ‘Neuroendocrine Carcinoma of the skin’ is a rare skin cancer type, with a high potential of metastasising and having chances of recurring within 3 years of initial prognosis. Research suggests that, ‘Merkel cells’ that are attached to the nerves do not have a direct role in the development of MCC. As causes of cancer are linked to damaged DNA’s, in cases of MCC, the phenomenon of inheritance seems to be less likely. Instead, research points out that several other factors such as prolonged UV exposure and fragile immune system can result in the development of MCC.

As per recent research findings, the common virus (Merkel cell Polyomavirus) that dwells on the human skin also has been linked as the causative agent of MCC. However, there is no enough evidence to claim, how the virus causes MCC. This cancer is fast-growing and can develop as painless bump on UV-exposed skin, however it can also spread to other areas of the body.

Causes

• The primary reasons for both, Non-Melanoma cancers (BCC, SCC and MCC) and Melanoma skin cancers is due to exposure to harmful UV radiations of the sun. Prolonged and intense exposure to the sun can damage the DNA in the skin cells, making them cancerous.
• Use of solariums or tanning beds that give artificial tan to the skin using UV radiations also increase the risk of developing skin cancer. There is nothing as ‘safe tan’ and these tanning units emit up to six times more UV rays than the midday sun of the summers. And thus, can facilitate growth of cancerous skin cells.
• Race and Colour too act as potential causative agents of skin cancer. As individuals with white-skin are at an increased risk of developing skin cancer, due to lack of Eumelanin pigment that acts as a protective guard of the skin against the harmful UV radiations.
• Weakened immune system due to any medical conditions, viral infections, suppression of the immune system due to organ transplantation can be potential causes of Non-Melanoma skin cancers.

As the cancer cells generally tend to rise in the body, the immune system destroys them before a new tumour is established. Thus, as the immune system become fragile, the cancerous cells have a chance to grow.

• IARC (International Agency for Research on Cancer) which is an entity of WHO (World Health Organisation) has classified ‘Arsenic’ and ‘Inorganic Arsenic compounds’ as carcinogenic to humans.

Arsenic is a naturally occurring chemical present in water, air and soil. Therefore, practising safe consumption of water, food and irrigation to crops preventing ingestion of arsenic/arsenic compounds through any mediums is paramount.

• Though the environmental factors get a major accountability in the development of all skin cancer types, some proportion of inheritance/genetics can also be the contributors.

The external triggers cause genetic modifications within single cells, that enable the development of cancer. Melanoma skin cancer tends to be genetic and is more common in patients with cancerous history.

• With age, the risk of skin cancer tends to increase due to accumulated skin exposure to the UV radiations of the sun, which eventually and gradually cause damage to the skin cells.

Symptoms

The symptoms of BCC include

• A pearl-like waxy lump on the skin surface or a flattened fresh brownish lesion resembling a scar.
• A re-occurring sore that bleeds/scabs

The symptoms of SCC include

• A firm reddish or pinkish nodule on the skin surface
• A hardened crusty, scaly scab/lesion
• A raised area of the skin surface or wart-like growth

The symptoms of Melanoma include

• A large brown coloured spot with dark blotches
• A mole that modifies in shape/colour/size/texture or the one that bleeds
• A small irregularly shaped lesion that appears pink, red, white, blue or bluish-black
• An itchy or painful lesion with a burning sensation
• Darkened lesions on the palms/fingertips/toes/soles or the mucosal membranes of the nose, mouth, anus or vagina

The symptoms of MCC include

• A reddish-pink or purple spot that keeps on growing
• It appears like an enlarging cyst but is often painless
• A rapidly growing dome-shaped mass on the skin
• Any spot that is changing, enlarging or that can result into bleeding.

Treatment

The skin cancer treatment varies and is based on the size, depth, type and location of the skin lesions. The removal of small cancerous growth on the outer skin surface is limited to the skin biopsy and does not require any further treatment. However, in severe cases of skin cancer, additional treatments include:

Freezing/Cryotherapy:

This is an effective treatment for excision of small and initial stage cancers by freezing them using liquid Nitrogen. Later, the dead skin cells shed off as they defrost.

Surgery:

This treatment is suitable for any skin cancer type. The cancerous growth is extracted or cut off along with a marginal portion of healthy skin in certain cases.

Mohs Surgery:

This surgical treatment is used for removing large, recurrent skin cancers such as BCC/SCC. It is an effective option to use on areas such as nose, which requires conservation of skin. The cancerous growth is extracted layer by layer, until no abnormal cancerous growth or cell remains which is done by microscopic examination. Thus, this process is a convenient option which helps in preserving the healthy skin.

Curettage and Electrodessication/Cryotherapy:

As most of the cancerous growth is extracted, the remaining cancerous layer is debrided using a surgical blade or curette. The rest of the cancerous tissue are dried off by using high frequency electric current using an electric needle. Variably, even liquid nitrogen can be used to freeze the cancerous growth on the borders and the base. This procedure can be used to treat BCC or thin layers of SCC.

Radiation:

This therapy is suitable when cancerous growth cannot be removed completely using surgical excisions. Radiation uses intense and high-powered beams of energy (X-rays) to destroy the cancerous tissue.

Topical and Systemic Chemotherapy:

In this therapy, drugs are used to kill or destroy the cancerous cells. The cancerous growths on the upper or outermost skin layer can be treated using topical applications such as creams/lotions containing anti-cancer agents, which is termed as ‘Topical Chemotherapy’.

However, Systemic Chemotherapy can be used if the skin cancer has spread to other areas or organs of the body. In this type, the drugs are administered orally or intravenously. These drugs pass through the blood stream and attack the cancerous cells that have spread to other organs or lymph nodes.

Photodynamic therapy:

This therapy uses a combination of a drug (photosensitizing agent) and specific beam of light, that produces active form of oxygen and kills the cancerous cells.

Biological therapy:

Unlike Chemotherapy, Biological therapy uses living organisms/ substance sourced from living organisms/laboratory versions of the same. It enables to stimulate the immune system of the body to work against the cancerous cells.

References

1. https://www.mdpi.com/2227-9059/6/1/6
2. https://www.ncbi.nlm.nih.gov/books/NBK247164/
3. https://www.ncbi.nlm.nih.gov/pubmed/26612377
4. https://www.ncbi.nlm.nih.gov/books/NBK441949/