Malignant melanoma
D E FI N I T ION
Malignancy arising from neoplastic transformation of melanocytes, the
pigment-forming cells of the skin. The leading cause of death from skin disease.
AE T IOLOGY
DNA damage in melanocytes caused by ultraviolet radiation results in
neoplastic transformation. 50 % arise in pre-existing naevi, 50 % in previously normal skin.
Four histopathological types:
1. Superficial spreading (70 %): Typically arises in a pre-existing naevus, expands in radial
fashion before vertical growth phase.
2. Nodular (15 %): Arises de novo, aggressive, no radial growth phase.
3. Lentigo maligna (10 %): More common in elderly with sun damage, large flat lesions,
follow an indolent growth course. Usually on the face.
4. Acral lentiginous (5 %): Arise on palms, soles and subungual areas. Most common type
in non-white populations.
E P IDEMIOLOGY
Steadily increasing incidence, 6,000/year diagnosed in the United
Kingdom, lifetime risk 1 in 80 in the USA. White races have 20 times increased risk to
non-white races.
H ISTORY
Change in size, shape or colour of a pigmented skin lesion, redness, bleeding,
crusting, ulceration.
EXAMINA T I ON ABCD
criteria for examining moles:
A Asymmetry.
B Border irregularity/bleeding.
C Colour variation.
D Diameter >6mm.
E Elevation.
INVE S T I G A T IONS
Excisional biopsy: For histological diagnosis and determination of Clark’s levels or Breslow
thickness.
Lymphoscintigraphy: Radioactive compound is injected around lesion and dynamic images
are taken over the course of 30 min to trace the lymph drainage and the sentinel node(s).
Sentinel lymph node biopsy (if primary and < 1mm depth): Sentinal lymph nodes are
dissected and histologically examined for metastatic involvement.
Staging: Imaging by ultrasound, CT or MRI, CXR.
Blood: LFT (liver is a common site of metastases).
MANAGEMENT
Primary prevention: Limit sun overexposure, avoid sunburn.
Wide local excision, margin dependent on depth of invasion (< 1mm: 1 cm, 1–4 mm:
2 cm margin). Skin grafting may be required.
Chemotherapy: May be necessary as adjunctive treatment or in metastatic disease.
Commonly used agents used are dacarbazine (20%respond), cisplatin, temozolomide
and vinblastine.
Biological therapy: Interferon a-2b, IL-2, and bevacizumab (unlicensed) have been shown
to potentially beneficial.
COM P L IC A T I ONS
Lymphoedema may result after block dissection of lymph nodes.
PROGNOSIS
5-year survival 90–95 % for lesions < 1.4 mm, 40 % with node-positive
disease and mean survival of 9 months with metastatic disease.
Poorer prognostic indicators: Ulceration, " mitotic rate, trunk lesions compared with limb.
Males poorer prognosis than females.
DERMATOLOGY 303
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