Types of Melanoma
There are four main types of melanoma, Superficial spreading melanoma, Nodular melanoma, Lentigo malignant melanoma and Acral melanoma
Rarely, melanoma can start in parts of the body other than the skin. It can start in the eye (ocular melanoma). Or it can start in the tissues that line areas inside the body, such as the anus or rectum (anorectal melanoma), nose, mouth, and other areas.
Superficial spreading melanoma
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 discoloured patch that has irregular borders and is somewhat asymmetrical in form.
The colour 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.
Ocular melanoma, or melanoma of the eye, is the most common primary eye tumour in adults and the 2nd most common melanoma (after cutaneous melanoma)
Like other melanomas, it begins in the melanocytes – the cells that produce the pigment melanin that colours the skin, hair, and eyes, as well as forms moles.
Uveal melanoma: The Ufa is a three-layered part of the back of the eye. It is made up of the choroid, iris and ciliary body. Uveal melanoma can form in any of the three layers and is named for where it forms.
Melanoma in the iris occurs in the front, the coloured part of the eye. Iris melanomas usually grow slowly and do not typically metastasize, or spread, to other parts of the body outside the eye.
Ciliary body melanomas occur in the back part of the eye and are grouped by the size of the tumour. Melanomas in the ciliary body tend to grow and metastasize to the liver more quickly than iris melanomas.
Choroidal melanoma: Choroidal melanoma is the most common subtype of uveal melanoma. Choroidal melanoma begins in the layer of blood vessels – the choroid – beneath the retina.
Conjunctival melanoma: Conjunctival melanoma is very rare.
It often appears as a raised tumour and may contain little or even no pigment, or colour. Conjunctival melanoma most commonly occurs in the bulbar conjunctiva – the mucous membrane that covers the outer surface of the eyeball.
Unlike other forms of eye melanoma that spread most often to the liver, when Conjunctival melanoma spreads, it most often spreads to the lungs.
WHAT IS NODULAR MELANOMA?
In nodular melanoma, malignant melanoma cells proliferate downwards through the skin – this is known as vertical growth.
The lesion presents as a nodule (lump) that has been rapidly enlarging over the previous weeks to months.
It can arise in normal-appearing skin, or within an existing melanoma of the other type.
A nodular melanoma can penetrate deeply within the skin within a few months of its first appearance.
Who gets nodular melanoma?
Nodular melanoma accounts for about 15% of melanoma in Australia and New Zealand.
Although more common in very fair skin (skin phototype 1 and 2), it may also occur in those who tan quite easily (phototype 3), and occasionally with brown or black skin (prototype 4-6).
Nodular melanoma is more common in males than females. Most are over the age of 50 when it is diagnosed.
The main risk factors for nodular melanoma are:
Previous invasive melanoma or melanoma in situ
Many melanocytic naevi (moles)
Multiple funny-looking moles
Fair skin that burns easily
It is less strongly associated with sun exposure than superficial spreading and lentigo maligna types of melanoma.
What does nodular melanoma look like?
Nodular melanoma may arise on any site, but is most common on exposed areas of the head and neck.
Nodular melanoma presents as a rapidly enlarging lump (over several weeks to months). The characteristics of nodular melanoma include:
A larger size than most moles – >6 mm and often a centimetre or more in diameter at diagnosis
Dome-shaped, often symmetrical firm lump
Single colour or variable pigmentation – most often black, red or skin coloured
Smooth, rough, crusted or warty surface
Ulceration or bleeding
Itching or stinging
One-third of nodular melanomas are not pigmented. They lack the ABCD melanoma warning signs. (Asymmetry, Border irregularity, Colour variation, large Diameter).
Certain melanomas may have no colour at all.
Physicians refer to these as “amelanotic” melanomas, because they are conspicuously missing melanin, the dark pigment that gives most moles and melanomas their colour.
These unpigmented melanomas may be pinkish-looking, reddish, purple, normal skin colour or essentially clear and colourless.
The problem is, patients and even physicians may not immediately recognise these as possible melanomas.
Even today’s specialised computer apps for early melanoma recognition tend to be modelled on the classic ABCDEs and can miss more clinically subtle melanomas like these.
Amelanotic melanomas can resemble other skin cancers like basal cell or squamous cell carcinoma, or worse, may be mistaken for benign moles, scars or cysts.
This can delay diagnosis, which may prove dangerous, since early detection of melanoma is critical; early melanomas are almost always curable, while those that advance beyond stage I become more difficult to treat.
Amelanotic melanomas tend to recur or spread (metastasize) more often than melanomas with more typical features.
While these melanomas lack pigment, they may have other melanoma warning signs to stay on the lookout for, such as asymmetry and an irregular border.
In addition, more and more physicians today stress the importance of the “E” in the ABCDEs – evolution or change
What is Subungual Melanoma?
A melanoma is a type of cancer that develops from cells, called melanocytes.
Melanocytes are cells that produce melanin; the pigment that gives skin its colour.
Melanoma of nail unit is a melanoma that affects the nail – either the fingernail or the toenail.
There are 3 main types of nail unit melanoma and these include:
Subungual Melanoma is melanoma of the nail affecting the tissue beneath the nail base, also known as the nail matrix. It is the region from where the nail forms and grows
Acral Lentiginous Melanoma
Acral lentiginous melanoma is a type of melanoma arising on the palms or soles.
Although acral lentiginous melanoma is rare in Caucasians and people with darker skin types, it is the most common subtype in people with darker skins.
It is more common on the feet than on the hands. It can arise in normal appearing skin, or it can develop within an existing melanocytic naevus (mole).
Acral lentiginous melanoma starts as a slowly enlarging flat patch of discoloured skin.
At first, the malignant cells remain within the tissue of origin, the epidermis. This is the ‘in-situ’ phase of melanoma, which can persist for months or years.
Acral lentiginous melanoma becomes invasive when the melanoma cells cross the basement membrane of the epidermis and malignant cells enter the dermis.
A rapidly-growing nodular melanoma can also arise within acral lentiginous melanoma and proliferate more deeply within the skin.
Who gets acral lentiginous melanoma?
Acral lentiginous melanoma is relatively rare compared to other types of melanoma.
There is no connection with the colour of skin (skin phototype) and it occurs at equal rates in white, brown or black skin.
Acral lentiginous melanoma accounts for 29-72% of melanoma in darker-skinned individuals, but less than 1% of melanoma in fair skinned people, as they are prone to more common sun-induced types of melanoma such as superficial spreading melanoma and lentigo maligna melanoma.
Acral lentiginous melanoma is equally common in males and females. The majority arise in people over the age of 40.
The cause or causes of acral lentiginous melanoma are unknown. It is not related to sun exposure.
What does acral lentiginous melanoma look like?
Acral lentiginous melanoma on palm, soles or fingers and toes start off as an enlarging patch of discoloured skin. It is often thought at first to be a stain. It can also be amelanotic (non-pigmented, usually red in colour). Like other flat forms of melanoma, it can be recognised by the ABCDE rule: Asymmetry, Border irregularity, Colour variation, large Diameter and Evolving.
The characteristics of acral lentiginous melanoma include:
Large size: >6 mm and often several centimeters or more in diameter at diagnosis
Variable pigmentation: most often a mixture of brown, and blue-grey, black and red colours
Smooth surface at first, later becoming thicker with an irregular surface that may be dry or warty
Ulceration or bleeding
Lentigo Malignant Melanoma
Lentigo maligna melanoma.
This type grows from pigmented areas of skin known as lentigo maligna.
This type is common with older people. Since it appears on only the part of the skin that is mostly exposed to the sun, the face is mostly the target area.
It is flat. It grows from within to the outside layer of the skin. There is the tendency for it to grow bigger and deeper over the years which can lead to a lumpy formation.
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.
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.
Lentigo maligna is the most common form of melanoma in Hawaii. When this cancer becomes invasive, it is referred to as lentigo maligna melanoma.