Melanoma

Melanoma is a malignant tumor of melanocytes, commonly arising in the skin but can occur in mucosal surfaces and the eye. It is highly aggressive with potential for early metastasis.

Definition

Melanoma is a malignant tumor of melanocytes, commonly arising in the skin but can occur in mucosal surfaces and the eye. It is highly aggressive with potential for early metastasis.

Epidemiology

Accounts for ~1% of skin cancers but causes the majority of skin cancer deaths
Higher incidence in fair-skinned populations and regions with high UV exposure
Median age at diagnosis: 55–60 years
Slight male predominance in older adults; females more affected in younger age groups
Incidence increasing globally due to UV exposure and improved detection

Etiology

Ultraviolet (UV) radiation exposure, including sunlight and tanning beds
Genetic predisposition: familial atypical multiple mole melanoma (FAMMM) syndrome, CDKN2A mutations
Dysplastic nevi and multiple moles
Skin type I–II and fair complexion
Immunosuppression increases risk (transplant recipients, HIV)

Pathophysiology

Malignant transformation of melanocytes due to UV-induced DNA damage
Mutations in BRAF, NRAS, KIT, or TP53 contribute to uncontrolled proliferation
Tumor growth follows radial phase (horizontal spread) then vertical phase (invasion into dermis and metastasis)
Lymphatic and hematogenous spread occurs early
Angiogenesis and immune evasion facilitate metastasis