Know: Types of Melanoma

Susana Fares Mazloum

Defining the disease

Melanoma is defined as a type of skin cancer that usually begins in melanocytes (pigment-producing cells). This type of cancer normally occurs in areas that tend to occasionally be sun-exposed. Melanoma can be seen to develop at any age in humans but the highest number of cases frequently occur in people during their fifties and seventies, yet, in the recent years it is becoming more common to be found in teenagers and young adults.

Melanomas are usually new growths on skin but they may also develop from an already existing mole or other skin growth that once was normal but became malignant over time. Most melanomas are known to affect only the epidermis (outermost layer of the skin) and if a melanoma ends up becoming thicker to the point of involving multiple layers of the skin anatomy, it can unfortunately undergo metastasis (spread to other parts of the body).

Epidemiology and causes

It is stimated that in the United States, melanoma affect 30 in 100,000 men yearly, becoming the fifth most common cancer type diagnosed in men and the sixth in women since it is stimated to affect 18 in 100,000 women yearly, as well. Research also demonstrates that 1 in 43 individuals will most likely develop melanoma in their lifetime, and light-skinned individuals have a 20 percent higher chance of developing melanoma than those with a dark-skin complexion.

The causes of the disease are mainly well understood, it comes from a combination of environmental and genetic factors. According to science, the greatest environmental risk factor is exposure to ultraviolet (UV) radiation from the sun, that lead to the accumulation of genetic mutations within the affected area. In most of the cases, melanoma is seen to be sporadic, this means that the genetic mutations occurred during a person’s lifetime, instead of genetic inheritance. Melanoma caused by inherited genetic changes is only seen in 10 percent of diagnosed cases.

Types of melanoma

Currently, there are four main types of skin melanoma: Superficial spreading, nodular, lentigo maligna, and, acral lentiginous melanoma.

melanoma
Malignant Melanoma Types. (a) Superficial Spreading Melanoma. (b) Nodular Melanoma (c) Lentigo malignant Melanoma. (d) Acral Lentiginous Melanoma. Credit: Abbas Hanon AlAsadi

 

In superficial spreading melanoma, the most common type is usually found on the arms, legs, chest and back. Here, the growth of melanoma cells tend to be slow at first, and it can spread out across the surface of the skin. On the other hand, nodular melanoma, the second most common type, is seen too grow more quickly than other types of melanomas. The tumor is known for losing its colour when starting to grow, becoming red rather than black. It can also be found on the chest, back, head or neck. Moreover, lentigo maligna melanoma is less common from the previously described, most of the cases are found to happen in older people, specifically in areas of skin that have had a lot of sun exposure over many years, such as the face and neck. It is known to develop from a slow-growing precancerous condition called a lentigo maligna or Hutchinson’s freckle that looks like a stain on the skin. As they are slow-growing, therefore, they are less dangerous than the other types of melanoma. Finally, acral lentiginous melanoma is the rarest type, it commonly affects the palms of the hands, soles of the feet, or under finger and toe-nails. This type of melanoma, is the only one more common to develop in people with darker skin. Researchers believe that this particular type is not related to sun exposure.

There are other types of melanoma considered rare, such as, desmoplastic melanoma. Also, melanoma can be seen to start in parts of the body other than the skin. An example is when it initiates in the eye, called ocular melanoma. Or it can start in the tissues that line areas inside the body, such as, nose and mouth.

In conclusion, melanoma is still a difficult disease to control. However, nowadays science has granted us with a considerate amount of knowledge regarding this disease behavior and by analyzing the old and new concepts regarding its pathology, we are able to simplify and enhance our approach to its treatment and the most important, its prevention.

Reference:
Melanoma – Genetics Home Reference – Nih