Early signs of melanoma are summarized by the mnemonic "ABCDEF":
Asymmetry
Borders (irregular with edges and corners)
Colour (variegated)
Diameter (greater than 6 mm (0.24 in), about the size of a pencil eraser)
Evolving over timeThis classification does not apply to nodular melanoma, which has its own classifications:
Elevated above the skin surface
Firm to the touch
GrowingMetastatic melanoma may cause nonspecific paraneoplastic symptoms, including loss of appetite, nausea, vomiting, and fatigue. Metastasis (spread) of early melanoma is possible, but relatively rare; less than a fifth of melanomas diagnosed early become metastatic. Brain metastases are particularly common in patients with metastatic melanoma. It can also spread to the liver, bones, abdomen, or distant lymph nodes. Cause
Melanomas are usually caused by DNA damage resulting from exposure to UV light from the sun. Genetics also play a role. Melanoma can also occur in skin areas with little sun exposure (i.e. mouth, soles of feet, palms of hands, genital areas). People with dysplastic nevus syndrome, also known as familial atypical multiple mole melanoma, are at increased risk for the development of melanoma.Having more than 50 moles indicates an increased risk melanoma might arise. A weakened immune system makes cancer development easier due to the bodys weakened ability to fight cancer cells. UV radiation
The UV radiation from tanning beds increases the risk of melanoma.
Vitamin D deficiency is also more common after surgical procedures that reduce absorption from the intestine, including weight loss procedures. Critical illness
Vitamin D deficiency is associated with increased mortality in critical illness. People who take vitamin D supplements before being admitted for intensive care are less likely to die than those who do not take vitamin D supplements. Additionally, vitamin D levels decline during stays in intensive care. Vitamin D3 (cholecalciferol) or calcitriol given orally may reduce the mortality rate without significant adverse effects. Breastfeeding
Infants who exclusively breastfeed need a vitamin D supplement, especially if they have dark skin or have minimal sun exposure. The American Academy of Pediatrics recommends that all breastfed infants receive 400 international units (IU) per day of oral vitamin D.

Pathophysiology
Decreased exposure of the skin to sunlight is a common cause of vitamin D deficiency. People with a darker skin pigment with increased amounts of melanin may have decreased production of vitamin D. Melanin absorbs ultraviolet B radiation from the sun and reduces vitamin D production. Sunscreen can also reduce vitamin D production. Medications may speed up the metabolism of vitamin D, causing a deficiency.The liver is required to transform vitamin D into 25-hydroxyvitamin D. This is an inactive metabolite of vitamin D but is a necessary precursor (building block) to create the active form of vitamin D.The kidneys are responsible for converting 25-hydroxyvitamin D to 1,25-hydroxyvitamin D. This is the active form of vitamin D in the body.