Most people have heard of the skin cancer called melanoma, and each year, 55,000 Americans are diagnosed with it. So what exactly is melanoma? Melanoma is the most serious type of skin cancer. If it's diagnosed early, melanoma is usually curable, however if the cancer goes unnoticed and spreads, it can be fatal. Here's how melanoma develops. Melanoma begins in skin cells called melanocytes which produce a pigment called melanin, the agent that gives skin its color and protects the body from sun damage. When you spend time in the sun, the melanocytes make more protective melanin, causing your skin to tan. If you receive too much sunlight, however, the melanocytes may begin to mutate and turn cancerous. Individuals with a family history of melanoma are much more likely to develop this form of cancer. Still, everyone is at some risk, so being safe in the sun is imperative. Because melanoma occurs in the cells that give skin its color, this form of cancer usually appears as a spot of darkened pigment, or a mole. The patterns of melanoma are often predictable. In men, it usually appears between the shoulders and hips, and on the head and neck. Women tend to develop melanoma on their lower legs. The best way to spot melanoma is to get to know your skin. Be aware that if you have more than 50 moles, you are a more likely candidate to develop melanoma! ABCDE is an acronym that stands for the five warning signs of melanoma. When examining a mole, be aware that any of these aspects can be indicative of melanoma. 'A' stands for an asymmetrical, or oddly shaped, mole. 'B' is for a mole with uneven borders. 'C' stands for color - a variety of colors within a mole is a warning signal. 'D' is for a mole with a diameter bigger than a pencil eraser. And 'E' stands for a growth that evolves over time. Melanomas fall into four basic categories. Three of them begin in situ, meaning they occupy only the top layer of skin. The fourth, nodular melanoma, is more serious because it penetrates more quickly into the skin. The first type of in situ cancer, superficial spreading melanoma, accounts for almost 70% of cases. This cancer spreads along the top layer of skin for some time before penetrating. Younger people often get the superficial spreading type. Lentigo maligna is most often found in the elderly. It's similar to superficial spreading melanoma, as it also remains close to the skin's surface for a long time. Acral lentiginous melanoma is the most common form found in those with darker skin types. It follows the same spreading pattern as the other in situ types, but usually appears under the nails, on the soles of the feet, or on the palms of the hands. The most aggressive form of this disease, nodular melanoma, is inherently invasive. Nodular melanoma makes up 10% to 15% of cases. If left untreated, melanoma can be fatal, so it's vital to be familiar with your skin. If you notice any abnormalities, please see a doctor immediately. Want to know more? Check out other videos and sources on this site for more information.