Superficial spreading melanoma

What you should know: This is the most common form of melanoma.

How and where it grows: It can arise in an existing mole or appear as a new lesion. When it begins in a mole that is already on the skin, it tends to grow on the surface of the skin for some time before penetrating more deeply. While it can be found nearly anywhere on the body, it is most likely to appear on the torso in men, the legs in women and the upper back in both.

What it looks like: It may appear as a flat or slightly raised and discolored, asymmetrical patch with uneven borders. Colors include shades of tan, brown, black, red/pink, blue or white. It can also lack pigment and appear as a pink or skin-tone lesion (amelanotic).

Lentigo maligna

What you should know: This form of melanoma often develops in older people. When this cancer becomes invasive or spreads beyond the original site, the disease is known as lentigo maligna melanoma.

How and where it grows: This form of melanoma is similar to the superficial spreading type, growing close to the skin surface at first. The tumor typically arises on sun-damaged skin on the face, ears, arms or upper torso.

What it looks like: It may look like a flat or slightly raised, blotchy patch with uneven borders. Color is usually blue-black, but can vary from tan to brown or dark brown.

Acral lentiginous melanoma

What you should know: This is the most common form of melanoma found in people of color, including individuals of African ancestry.

How and where it grows: It often appears in hard-to-spot places including under the nails and on the soles of the feet or palms of the hands.

What it looks like: It may appear as a black or brown area.