Melanoma is a serious and fatal skin cancer that develops out of the cells (melanocytes) that produce skin pigment (melanin). Due to cell DNA mutation caused by the radiation of the sun, a change can occur in these melanocytes that allows them to rapidly and uncontrollably reproduce, forming a tumor. Many times, this tumor is benign, as the cells stop reproducing and expanding. The tumor that results from this is called a nevi, also known as a common mole or freckle. However, when these cells continue to uncontrollably reproduce, they form a malignant cancer called melanoma. Of all skin cancers, melanoma is the most dangerous as it can spread, or metastasize, to other organs in the body. This results in organ failure and death as the cancer increases. Melanomas occur all over the body, and certainly do form in the feet, even in areas where the sun does not radiate into.

Melanoma can come in several different forms. Superficial spreading melanoma is the most common type, with a slow growing mass that moves outward. Nodular melanoma is next most common, and appears as a deeper mass rather than on that spreads outward. Since it is deeper, it has a worse prognosis. In African-Americans, the most common type is called acral lentinginous melanoma. This melanoma involved the palms, soles, and nail area. Many people with increased skin pigment have pigmented streaks in their nails, seen as thin dark lines running the length of the nails. When the streaks are wider, darker, or otherwise different looking from the other streaks, or when this darkness extends into the skin, a serious concern for melanoma must be made. Two other forms of melanoma, lentigo malignant melanoma, and amelanotic melanoma, are less common. Lentigo maligna melanoma develops from a benign lesion called lentigo maligna, which is a common benign pigmented mole. It slowly grows over the course of decades. Amelanotic melanoma is melanoma that has no pigment. This can be a particularly dangerous form in that the lesion does not have color most people associate with melanoma, and the cancer can go undiagnosed until it becomes particularly large.

Melanomas are diagnosed partly on the basis of a medical exam, and partly through a microscopic evaluation of the lesion's tissue, which confirms the diagnosis. While skin moles are common, and often present from birth in the form of a birthmark, there are characteristics that make melanomas stand out. The ABCDE system helps with this on a medical exam of the skin. A stands for asymmetry. A benign mole should have an even shape from one side tot he other. Malignant lesions have irregular, uneven patterns to their shape in general. B stands for border. Benign lesions have a smooth border, while malignant lesions are generally scalloped or ragged. C stands for color. While benign moles can be very dark in color, the color itself will be consistent. In a malignant lesion, the color will be uneven, with some areas light and some darker (except for amelanotic melanoma where there is no color). D stands for diameter. Malignant moles tend to be more than 6 mm in diameter, although this is not absolutely true. E stands for evolving. Benign lesions remain the same, while malignant ones change, becoming bigger, thicker, darker, or more irregular. Using this system to evaluate lesions can help identify which ones are concerning, however only a microscopic evaluation can confirm the diagnosis. This is done to be certain of a suspected melanoma, or to simply assess a lesion that a physician is not sure of. By taking a biopsy of the lesion, either by taking a core of skin in all its layers (punch biopsy), or by removing a complete wedge of skin with the lesion (excisional biopsy), a physician can consult a pathologist who will look at the sample under a microscope and determine if the cells are cancerous. Most importantly, a pathologist will determine the depth of the melanoma, which has great bearing on treatment and survival.

Melanoma is treated very aggressively, as it can be lethal if it spreads. The immediate area of skin where the lesion sits is removed in a wide pattern, and in some cases if there is not enough surrounding tissue (like in a toe), the part of the body is amputated to prevent the cancer from spreading. The lymph system (a fluid drainage system that cancer uses to spread) is assessed to see if the cancer has spread from the original site, and body scans are used to detect any internal cancer process. Chemotherapy and radiation therapy can be used, but are not as successful as when used in other cancers.