melanoma
MELANOMA
Melanoma is a skin neoplasm that originates from malignant transformation of melanocytes.
It commonly occurs in the extremities of women and on trunk or head and neck in men.
Metastases are via lymphatic and hematogenous routes.

Introduction

  • 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
  • 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: >60 years
    • 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, BRCA2, 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
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