From this point on, melanoma is capable of spreading. The Breslows depth of the lesion is usually less than 1 mm (0.04 in), while the Clark level is usually 2. The vertical growth phase (VGP) following is invasive melanoma. The tumor becomes able to grow into the surrounding tissue and can spread around the body through blood or lymph vessels. The tumor thickness is usually more than 1 mm (0.04 in), and the tumor involves the deeper parts of the dermis. The host elicits an immunological reaction against the tumor during the VGP, which is judged by the presence and activity of the tumor infiltrating lymphocytes (TILs). These cells sometimes completely destroy the primary tumor; this is called regression, which is the latest stage of development. In certain cases, the primary tumor is completely destroyed and only the metastatic tumor is discovered. About 40% of human melanomas contain activating mutations affecting the structure of the B-Raf protein, resulting in constitutive signaling through the Raf to MAP kinase pathway.An insult common to most cancers is damage to DNA. UVA light mainly causes thymine dimers. UVA also produces reactive oxygen species and these inflict other DNA damage, primarily single-strand breaks, oxidized pyrimidines and the oxidized purine 8-oxoguanine (a mutagenic DNA change) at 1/10, 1/10, and 1/3rd the frequencies of UVA-induced thymine dimers, respectively. If unrepaired, CPD photoproducts can lead to mutations by inaccurate translesion synthesis during DNA replication or repair.
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.