Types of melanoma

Superficial spreading melanoma

What It Is: The most common type of melanoma, representing about 70% of all cases. It begins in the melanocytes and spreads on the surface of the skin before it grows deeper and becomes invasive. This type of melanoma usually appears as a flat or barely raised lesion on the surface of the skin, often with irregular borders and variations in colour. About half of these melanomas occur in pre-existing moles; the other half occur in new lesions.¹

How It Progresses: It spreads along the top layer of skin (the epidermis) for a period of months to years before it goes deeper into the skin.

Signs: The darkening in one part of a pre-existing mole or the appearance of a new mole on unaffected, normal skin.

Nodular melanoma

What It Is: Nodular melanoma is the most aggressive type of melanoma and accounts for 10 to 15% of all cases of melanoma. Nodular melanoma usually appears on the trunk, head or neck and is more common in men than women.

How It Progresses: Unlike other melanomas that tend to grow across the surface of the skin (like an oil slick spreading), a nodular melanoma invades more deeply earlier and therefore often presents with a greater depth of invasion when it is diagnosed. For this reason, nodular melanomas are more frequently associated with a poorer prognosis than other melanomas.

Signs: This melanoma usually appears as a blue-black, dome-shaped nodule, although 5% of the time the lesions are pink or red.

Lentigo Maligna Melanoma

What It Is: This melanoma develops from a pre-existing lentigo, rather than a mole. A lentigo is a dark, flat or slightly raised, non-cancerous spot on the skin, also known as a sunspot.

How It Progresses: This type of melanoma typically takes many years to develop. It is most often found in elderly adults and on parts of the body that have been overexposed to the sun (i.e.  face, ears, arms, chest, and back)

Signs: Like superficial spreading melanoma, lentigo maligna melanoma usually grows slowly across the top layer of skin and generally appears as a large, slightly-raised patch containing differing shades of colour.

Acral Lentiginous Melanoma (ALM)

When to contact your doctor

If you are concerned about an area on your skin, make an appointment.

Don’t hesitate to ask for a second opinion if you think it’s warranted.

The less common types of melanoma

Amelanotic Melanoma (AM)

What it is: AM is a rare type of cutaneous melanoma, that is defined by its lack of colour, or lack of pigment. They can be colourless or red or pink. Although AM can occur on all body sites, it is more common on chronically sun-exposed areas.

How it progresses: AM can progress in a variety of ways. It is often diagnosed at a later stage than pigmented melanomas.

Signs: AM doesn’t contain melanin, so it does not look like a mole or appear like a mole. An AM may be a faint reddish or pinkish colour or it may have no colour at all; it may be an area of skin that simply looks different from that around it.

Desmoplastic Melanoma (DM)

What it is: DM is a rare type of melanoma that can occur on its own or in conjunction with another subtype of melanoma. Its development is related to chronic UV exposure and is often found on the head and neck, trunk, or extremities of older individuals.

How it progresses: DM is challenging because it presents and progresses in a variety of different ways and is often diagnosed at a later stage than other melanomas. It is described as an invasive melanoma because the malignant cells within the dermis layer of the skin are surrounded by fibrous tissue and they often infiltrate surrounding nerve fibres.

Signs: Desmoplastic melanoma can present in a number of ways, so it’s difficult to describe what to look for as it often lacks the ABCDE melanoma warning signs. However they often progress as a slowly enlarging area that resembles a scar or thickened lesion

Ocular Melanoma

Melanoma is considered a form of skin cancer because it develops in the melanocytes (i.e. the cells in our skin that produce pigment). Melanocytes also exist in other places in our body, including in our eyes, so melanoma can occur in our eyes, too. Melanoma of the eye is generally called ocular melanoma.

Ocular melanoma most often affects the middle layer of your eye (the uvea), which includes the coloured portion (the iris), the muscle fibres around the lens (ciliary body), and the layer of blood vessels that lines the back of the eye (choroid). This is called Uveal Melanoma. However, melanoma can also develop in the conjunctiva, the clear tissue that covers the white part of the eye and the inside of the eyelids. This is called Conjunctival Melanoma.

Uveal Melanoma

Margins are the area of normal tissue surrounding the melanoma. If there are melanoma cells in or very close to that area, more surgery may be required.

Conjunctival Melanoma

The mitotic rate is the measure of how fast melanoma cells are dividing and multiplying. When pathologists study a melanoma, they will count the number of actively dividing cells that they see. Averaging this number gives the mitotic count, and it is reported as the number of mitoses per square millimetre (mm²). (For example, ≤1 mitoses/mm².) A high mitotic count means more tumour cells are dividing at a given time and is associated with a worse prognosis.

Ocular Melanoma Risk Factors

• Light-coloured eyes (blue or green)
• Increasing age
• Pale or fair-coloured skin
• Certain genetic conditions or inherited skin conditions that cause abnormal moles
• Abnormal skin pigmentation involving the eyelids or increased pigmentation on the uvea
• A mole, lump or growth on or in the eye
• Exposure to natural sunlight or artificial sunlight (such as from tanning beds) over long periods of time (more specific to conjunctival)
•  Exposure to welding

Ocular Melanoma Symptoms

In its early stages, ocular melanoma may not cause any symptoms, but when symptoms do occur, they can include:

• A dark spot on the iris, the white of your eye, or conjunctiva
• Blurred or distorted vision
• The sensation of flashing or specks in your vision
• A change in the shape of the pupil
• Loss of peripheral vision

See an ophthalmologist immediately if you have any of the symptoms listed above.

Mucosal Melanoma

Mucosal melanoma can develop in the sinuses, nasal passages, oral cavity, vagina and vulva, and anus. Mucosal tissues contain melanocytes just as skin does, and those melanocytes can become cancerous.

Mucosal melanomas are rare, accounting for only about one percent of all cases of melanoma, but they tend to be more aggressive and have less favourable prognoses compared to cutaneous melanoma. Researchers have not been able to identify any risk factors: Neither UV exposure nor family history seems to play a role. It tends to develop later in life, with most people being diagnosed over the age of 65.

Mucosal Melanoma Symptoms

Depending on the site involved, the signs and symptoms of mucosal melanoma vary and may include:

• Nose bleeds, breathing difficulty, loss of sense of smell, or pain inside the nose
• Pigmented lesions/masses or ulcers inside the mouth, cheeks, or lips or dentures that stop fitting properly
• Pain or bleeding from the anus, or a protruding mass (very similar to haemorrhoid symptoms)
• Vaginal bleeding, discharge, pain or itching or a noticeable vulval mass
• Difficulty or pain during swallowing or speaking
• Blood in the urine or increased urinary frequency
• Abdominal pain on the right side of the abdomen
• Yellowed skin and whites of the eyes

Promptly see your doctor if you experience any of the above symptoms.

Melanomas with Unknown Primary (MUP)

In rare cases, melanoma is found to have spread to lymph nodes or organs, but the primary tumour site is unknown. When this type of melanoma occurs, it is called melanoma of unknown primary (MUP). Current hypotheses suggest that most of these melanomas originate on the skin and arise from:

• Melanomas of the skin that were incompletely removed
• “Regressed” melanomas occur when the body’s immune system may have destroyed a portion of the cancerous cells in the primary tumour, but not before some melanoma cells travelled into nearby lymph nodes or blood vessels
• Pigmented cells that travelled to the lymph nodes and were transformed into melanoma.

The treatment for MUP will vary depending on where the melanoma cells have been found. Interestingly, studies have shown that patients with MUP may have improved survival compared with melanoma of a known primary. It is thought that the body’s immune system may already have identified the malignant cells and launched an immune response²