Melanomas are highly malignant tumour of the skin' melanocytes (the cells that give skin its pigment). Lighter-skinned people, particularly when exposed to excessive sun, are more likely to experience the condition compared with darker-skinned individuals.
The 4 major types of melanoma are (in order of severity):
Lentigo maligna melanoma Rarely seen in the foot, this is the least-aggressive form.
Superficial spreading (pategoid) melanoma This is the most common form of melanoma. It is moderately aggressive.
Acral melanoma Common in the lower extremities, this form is the most common type seen in the feet of asian and black patients.
Nodular melanoma This is the most aggressive form of melanoma, and it may arise anywhere on the body.
Treatment of melanomas is based on the classification, so we'll briefly mention a couple of the classification systems.
Clark's Classification System is based upon the depth the lesion has invaded the layers of skin.
The problem with the Clark's classification is that the cell layers vary in thickness. In a location such as the sole of the foot (which has very thick skin), a lesion may only be a Level One lesion, yet actually extend fairly deeply. Another problem is that in some areas, a melanoma may stretch a layer of skin, so it may look like it penetrates to a deeper layer than it really does. A third problem is that the border between the papillary and reticular dermis is not always clear. Hence, the Clark's Classification system is more subjective than it should be.
The Breslow Classification System tries to take some of the subjectivity out of the equation. This system is purely based by the thickness of the lesion, regardless of the tissue plane into which it extends.
Where it's most likely to develop
Sun-exposed areas like the back, shoulders, arms and neck are the most frequent locations for melanomas to develop.
What it may look like
Most physicians will tell you to look for "ABCD" if you suspect a suspicious lesion:
A stands for asymmetry. Most moles and other similarly benign (non-cancerous) lesions are circular. Suspicious lesions are often more irregularly shaped.
B stands for border. Most benign lesions have regular, smooth borders. Irregular borders are suspicious.
C stands for colour. Most benign lesions are uniform in color. Suspicious lesions are more likely to be multi-coloured.
D stands for diameter. Be suspicious of lesions that grow larger than a pencil eraser.
I'll also add EFGHI:
E means you should examine the most common locations a melanoma might develop--the back, arms, neck and shoulders.
F stands for fragility. Suspicious lesions will often bleed slightly when scratched or touched.
G stands for growth. Suspicious lesions will often grow larger over time.
H stands for hurt. Suspicious lesions are more likely to be tender or irritated.
I stands for itchy. Suspicious lesions are more likely to become itchy.
Treatment involves performing a biopsy and sending it to a pathologist for review. Lymph nodes may also be examined. Additional surgery may be required, depending upon the extent of the lesion. Oncologists are consulted for possible chemotherapy and/or irradiation. And diagnostic radiologists are used to assess spread to other tissues throughout the body.