Melanoma is a form of skin cancer that arises from melanocytic cells which make the pigment melanin that colors the skin
May also occur in mucosal surfaces or other sites where neural crest cells migrate eg oral, genital and rectal mucosa, eyes and nail beds
Most serious form of skin cancer
Incidence increases with age
Predominantly occurs in adults, commonly on extremities in women and on trunk or head and neck in men
Metastases are via lymphatic and hematogenous routes
Common sites of metastases are under the skin, liver, lungs, brain and bone
In-transit metastases are skin or subcutaneous intralymphatic tumors that develop between the primary tumor and draining lymph nodes (LN)
Malignant melanoma may regress spontaneously but complete regression is <1%
Risk Factors
Risk factors include:
Gender: Men are at increased risk
Age: More than 50 years old
Sun exposure, tanning bed use
People geographically located near the equator
Fair skin and freckling: Less commonly, dark-skinned individuals may have melanoma and the nail beds, palms, and soles are frequently affected
Personal medical history: Sunburns, precancer or any malignancy especially actinic keratosis, keratinocyte skin cancer (basal cell carcinoma, squamous cell carcinoma), pediatric malignancy
Family history of cutaneous melanoma, pancreatic cancer, astrocytoma, uveal melanoma, mesothelioma
Genetic mutations: CDKN2a, CDK4, MC1R, BAP1
Suppressed immune system
Environmental exposures (ultraviolet A [UVA] or psoralen plus UVA [PUVA] therapies)
Increased numbers of nevi and pigmentation, eg familial atypical mole-melanoma syndrome, giant congenital nevi, dysplastic nevus syndrome
Malignant transformation in a nevus includes changes in size and shape including border changes, discoloration, changes in consistency, presence of inflammation, and satellites
Deep invasion of the skin by the melanoma is shown by an increase in size, ulceration, darkening, or bleeding
