What is melanoma? An introduction

Author: Vanessa Ngan, Staff Writer; Copy Editor: Clare Morrison; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, October 2013. About Melanoma is sponsored by the New Zealand Dermatological Society Incorporated.

Melanoma is a skin cancer

More about melanocytes and melanin

Melanocytes normally make a pigment called melanin.

Some different skin types are shown below.

Skin types
Skin burns. Does not tanSkin burns easily. Tans poorlySkin sometimes burns. Tans easilyLight brown skin. Rarely burns
Fitzpatrick Type 1 skin Fitzpatrick Type 2 skin Fitzpatrick Type 3 skin Fitzpatrick Type 4 skin

Different types of melanoma

There are several different types of melanoma. The differences between them determine what a melanoma looks like, how quickly it will grow, where it appears on the body and who is most likely to get one.

Thin melanoma

Thin melanomas include:

Thin melanomas
Superficial spreading melanomaLentigo malignaLentiginous melanomaAcral lentiginous melanoma
Superficial spreading melanoma Lentigo maligna Lentiginous melanoma Acral lentiginous melanoma

Thick melanoma

Thick melanomas include:

Thick melanomas
Nodular melanomaAmelanotic nodular melanomaSpitzoid melanomaDesmoplastic melanoma
Nodular melanoma Amelanotic nodular melanoma Spitzoid melanoma Desmoplastic melanoma

How do melanoma types relate to sun damage?

The behaviours of different types of melanoma vary according to the melanomas’ relationship to sun damage.

Chronic sun exposure

In New Zealand, melanoma often affects people who are sun damaged. This type of melanoma:

Intermediate sun exposure

Melanoma can also affect people who actually don't spend a lot of time outdoors. This type of melanoma is associated with earlier sunburn, and:

Differences in melanomas due to sun damage* and genetic predisposition^
Chronic sun damage*Close-up of melanoma*Many and unusual moles^Close-up of melanoma^
Chronic sun damage Lentiginous melanoma Many and unusual moles Malignant melanoma in man with many and unusual moles

Rare types of melanoma

Melanoma unrelated to sun exposure

Even people with very little exposure to the sun can get melanoma. Melanoma that is not associated with sun exposure:

Melanoma that starts in other parts of the body is much less common than melanoma that starts in the skin. These types of melanoma can grow quickly and are sometimes hard to diagnose.

Mucosal melanoma

Mucosal melanoma starts within a mucous membrane. These are the moist linings that cover body cavities and passages such as the mouth, nose and eyelids, and urinary and genital tracts.

Non-cutaneous melanoma

Melanoma may rarely start growing in melanocytes within the eye (uveal melanoma), the brain or spinal cord, the lymph glands, or elsewhere.

Primary and secondary melanoma

Melanoma is often described as primary or secondary.

Primary melanoma

Primary melanoma is the first sign of melanoma. It starts invisibly small within the skin (or rarely within another tissue) and grows over weeks to years.

Primary melanomas
Nodular melanomaSuperficial spreading melanomaLentigo malignaNail melanoma
Nodular melanoma Superficial spreading melanoma Lentigo maligna Nail melanoma

Secondary melanoma

Secondary melanoma is the sign that melanoma has spread to other tissues. This is also called advanced melanoma or metastatic melanoma. Secondary melanoma tends to grow quickly (often noticeable over several weeks).

Deposits of metastatic melanoma may grow within lymph nodes (glands) in the neck, armpit or groin. They may also grow within the skin, brain, lungs, liver or other organs.

In about 3% of patients presenting with secondary melanoma (metastasis), the primary tumour is never found.

Metastatic melanoma is detected clinically on examination or by PET-CT scan.

Secondary melanomas
Secondary melanoma in the skinMelanoma under the skinMelanoma in lymph glandsPET-CT scan:
metastasis glows in groin
Secondary melanoma in the skin Subcutaneous metastatic melanoma Secondary melanoma in the lymph glands of the groin PET-CT scan revealing metastatic melanoma in groin


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