Malignant Melanoma

November 12, 2012

Malignant Melanoma

With increasing reports of malignant melanoma every year, it is time that awareness and understanding of a disease that is now considered to be common also increases.


Malignant melanoma affects either the melanocytes or the cells that are produced from melanocytes. The numbers of cases of the disease continue to increase every year, as does the number of death it causes. The melanoma grows in two separate phases known as radial growth and vertical growth. The radial phase occurs first and as you might expect during this time, the melanoma grows in a radial movement within the epidermis. Eventually the second growth phase will begin and the melanoma will begin to grow vertically, invading the dermis as well as developing the ability to metastasize. The malignant melanoma can be classed according to the thickness of the lesion. Anything 1mm or less in depth is considered to be thin, anything between 1-4 mm in depth is considered moderate and anything greater than 4 mm in depth is considered to be think.

There are 5 different types of malignant melanoma known as:

Superficial Spreading Melanomas

This type accounts for approximately 70% of malignant melanomas. In most cases they develop from pigmented dysplastic nevus. Superficial spreading melanoma often occurs following changes to the nevus such as an ulceration, enlargement or colour change. It can develop on any area of skin but is most commonly found on the head, neck and trunk. It is also common for SSM to develop on the lower extremities in women.

Nodular Melanomas

This form can also develop anywhere on the surface of the body and is accountable for between 10-15% of all cases. In most commonly occur on the trunks of males. Nodular melanomas can usually be identified by the uniform symmetry and dark brown or black colour. The radial growth phase is not always obvious in this form of melanoma as it quickly develops into the second growth phase or the vertical phase.

Lentigo Maligna Melanomas

Once again this form accounts for around 10-15% of all cases. They can be most commonly be found on the skin surface that is commonly exposed to the sun such as the necks and hands. They often cover fairly large area and can have sections of hypppigmentation.

Acral Lentiginous Melanomas

This is the only form of melanoma that affects black people in the same amounts as white people. It is typically found on the palms of the hands as well as soles of the feel and subungual areas. This form is also very aggressive and moves quickly form the radial phase to the vertical phase of growth.

Mucosal Lentiginous Melanomas

This form only accounts for around 3% of diagnosed cases of malignant melanoma. It develops on any mucosal surface such as the conjunctiva, oral cavity, oesophagus, vagina, female urethra, penis and anus. It occurs most commonly in older people and are considered to be aggressive.

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