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 & rectal mucosa, eyes & nail beds
  • Predominantly occurs in adults, commonly on extremities in women & on trunk or head & neck in men
  • Metastases are via lymphatic & hematogenous routes
    • Common sites of metastases are under the skin, liver, lungs, brain & bone
    • In-transit metastases are skin or subcutaneous intralymphatic tumors that develop between the primary tumor & draining lymph nodes (LN)
  • Malignant melanoma may regress spontaneously but complete regression  is <1%

Risk Factors

  • Risk factors include:
    • Sun exposure
    • Fair skin & freckling: Less commonly, dark-skinned individuals may have melanoma & the nail beds, palms, & soles are frequently affected
    • Family & personal history of melanoma
    • Suppressed immune system
    • Environmental exposures [ultraviolet A (UVA) or psoralen plus UVA (PUVA) therapies]
    • Increased numbers of nevi & pigmentation, eg familial atypical mole-melanoma syndrome, giant congenital nevi, dysplastic nevus syndrome
  • Malignant transformation in a nevus includes changes in size & shape including border changes, discoloration, changes in consistency, presence of inflammation, & satellites
    • Deep invasion of the skin by the melanoma is shown by an increase in size, ulceration, darkening, or bleeding
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