Melanoma, also redundantly known as malignant melanoma, is a type of skin cancer that develops from the pigment-producing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye (uveal melanoma). In women, they most commonly occur on the legs, while in men, they most commonly occur on the back. About 25% of melanomas develop from moles. Changes in a mole that can indicate melanoma include an increase in size, irregular edges, change in color, itchiness, or skin breakdown.The primary cause of melanoma is ultraviolet light (UV) exposure in those with low levels of the skin pigment melanin. The UV light may be from the sun or other sources, such as tanning devices. Those with many moles, a history of affected family members, and poor immune function are at greater risk. A number of rare genetic conditions, such as xeroderma pigmentosum, also increase the risk. Diagnosis is by biopsy and analysis of any skin lesion that has signs of being potentially cancerous.Using sunscreen and avoiding UV light may prevent melanoma. Treatment is typically removal by surgery. In those with slightly larger cancers, nearby lymph nodes may be tested for spread (metastasis). Most people are cured if spread has not occurred. For those in whom melanoma has spread, immunotherapy, biologic therapy, radiation therapy, or chemotherapy may improve survival.
Desmoplastic melanoma
Melanoma with small nevus-like cells
Melanoma with features of a Spitz nevus
Uveal melanoma
Vaginal melanoma
Polypoid melanoma, a subclass of nodular melanoma. In situ or invasive
A melanoma in situ has not invaded beyond the basement membrane, whereas an invasive melanoma has spread beyond it. Some histopathological types of melanoma are inherently invasive, including nodular melanoma and lentigo maligna melanoma, where the in situ counterpart to lentigo maligna melanoma is lentigo maligna. Lentigo maligna is sometimes classified as a very early melanoma, and sometimes a precursor to melanoma.Superficial spreading melanomas and acral lentiginous melanomas can be either in situ or invasive, but acral lentiginous melanomas are almost always invasive. Staging
Further context on cancer staging is available at TNM. Metastatic melanomas can be detected by X-rays, CT scans, MRIs, PET and PET/CTs, ultrasound, LDH testing and photoacoustic detection. However, there is lack of evidence in the accuracy of staging of people with melanoma with various imaging methods.Melanoma stages according to AJCC, 8th edition:
TX: Primary tumor thickness cannot be assessed (such as a diagnosis by curettage)
T0: No evidence of primary tumor (such as unknown primary or completely regressed melanoma)Stage 1 and 2 require an N (lymph node) class of:

N0 – No regional metastases.Stage 1, 2 and 3 require an M (metastasis status) of:

M0: No evidence of distant metastasisOlder systems include "Clark level" and "Breslows depth", quantifying microscopic depth of tumor invasion.