malignant melanoma Flashcards
definition of malignant melanoma
malignancy arising from neoplastic transformation of melanocytes - the pigment forming cells of the skin
leading cause of death from skin disease
aetiology of malignant melanoma
DNA damage in melanocytes caused by UV radiation = neoplastic transformation
short periods of intense UV exposure - particularly in the early years
50% arise in pre-existing naevi, 50% in previously normal skin
different histopathological types of malignant melanoma
superficial spreading (70%)
nodular (15%)
lentigo maligna (10%)
acral lentiginous (5%)
superficial spreading melanoma
arise in pre-existing naevus
expoand in radial fashion before vertical growth phase
grow slow and met later
better prognosis than nodular
nodular melanoma
arise de novo
agressive
no radial growth phase
invade deeply
met early
may be amelanotic in 5%
lentigo maligna melanoma
more common in elderly with sun damahe
large flat lesions
follow an indolent growth cause
usually on the face
evolve from pre-existing lentigo maligna
acral lentiginous melanoma
arise on palms, soles and subungal areas
most common type in non-white populations
epidemiology of malignant melanoma
steadily increasing incidence
6000/yr dx in UK
lifetime risk 1 in 80 in US
white races have 20 times increased risk to non-white
commonly affects younger people
sx of malignant melanoma
change in size, shape or colour of pigmented lesion
redness
bleeding
crusting
ulceration
signs of malignant melanoma
ABCD criteria for examining moles
- A - asymmetry
- B - border irregularity/bleeding
- C - colour variation
- D - diameter >6mm
- E - elevation
Ix for malignant melanoma
excisional biopsy - for histological dx and determination of Clark’s levels or Breslow thickness
lymphoscintigraphy - radioactive compound is injected around the lesion and dynamic images are taken over course of 30mins to trace the lymph drainage and the sentinal nodes
sentinal LN biopsy (if primary and <1mm depth) - sentinal LN are dissected and histologically examined for met involvement
staging - US, CT, MRI, CXR
blood - LFT (liver common site of met)
Glasgow 7 point checklist for malignant melanoma
refer if 3 or more points, or with 1 point if suspicious
- change in size (2pts)
- change in shape (2pts)
- change in colour (2pts)
- inflammation (1pt)
- sensory change (1pt)
- dm >7mm (unless growth in a vertical plane) (1pt)
- Crusting/bleeding (1pt)
breslow thickness
depth of malignant melanoma in mm
prognostic factors for malignant melanoma
breslow thickness
tumour stahe
ulceration
summarise congenital malignant naevi
usually >1cm
present at birth or in the early noenatal period
if >20cm = increased risk of malignant change
summarise acquired melanocytic naevi
present in childhood or in young adults and have characteristic evolution
start as flat evenly pigmented naevi - nests of melanocytes collect along the basal layer of the epidermis = junctional naevi
as melanocytes migrate from the epidermis to the dermis - moles evlove into raised evenly pigmented dome-shaped naevi = compound naevi
then the epidermal component is lost and moles change into pale brown papules = intradermal naevia
disappear in old age
summarise halo naevi
common in adoplescence
a white halo develops around a benign melanocytic naevi
not sinister and results from loss of melanocytes by lymphocyte action
in adults - mayu indicate melanoma elsewhere - check skin, eyes and mucosal surfaces
definition of melanocytic naevi
benign neoplasms or hamartomas made of melanocytes
most commonly as small, brown, flat macules, raised mammillated dome-shaped papules, bluish-grey macules and papules, and even amelanotic skin-coloured papules.
Unless congenital, they first appear in childhood
more common in people with light skin and eyes.
epidemiology of melanocytic naevi
very common, >98% of white people have at least 1 by early childhood
usually between 15-40 acquired naevi - regress with increasing age
less common in Asian and black people
halo naevi <20yrs, on back
Congenital nevi are stated to occur in <2% of the population
Nevus spilus may be a congenital nevus with a prevalence of no more than 2% of the population
spitz naevia - children and younger adults, usually acquired
Atypical, dysplastic, or Clark’s nevi are sporadic or familial, are estimated to have an incidence of between 2% and 10%, and can be acquired throughout life
aetiology of melanocytic naevi
genetic predisposition for formation of the naevi is likely
acquired are more common in fair skin and light eyes
sun exposure - because associated with tendency to burn, and history of severe burns
increase in prev with decreasing latitude
pathology of melanocytic naevi
Melanocytes are neural crest-derived cells that migrate to the epidermis during embryogenesis
In addition to the epidermis, melanocytes are normally found in hair follicles, the uveal tract of the eye, the leptomeninges, and the cochlea.
sx and signs of melanocytic naevi
presence since birth
asymettrical, indistinct, irregularly borderd, variably coloured papules with dm >5mm
Atypical, dysplastic, or Clark’s nevi may have a ‘fried egg’ appearance, with a central papular component and a flat peripheral component, and may have indistinct borders.[26]
Larger than 5 mm, and may have variable coloration from pink to tan to brown.
history of change in shape and colour - become more raised or dome shaped, get lighter or darker over time, spitz have a history of growing rapidly
asymptomatic
multiple lesions
flat, brown macule - Junctional acquired nevi are often small, flat, uniformly brown macules.
dome shaped papule - Compound and dermal nevi are often dome-shaped and tend to have uniform pink, tan, or brown coloration.
light brown background with speckled darker brown spots within - nevus spilus
blue-grey dome shaped papule - Common blue nevi are solitary blue-grey to black papules or flat macules that are usually <1 cm and often found on the dorsal extremities, head and neck, and sacrum
central pink to brown papule with surrounding depigmented white ring - halo nevus
pinkish-brown papule - spit naevi often found on the face and lwoer extremities as pink or red-brown papules with a smooth or verrucous surface
RF for melanocytic naevi
genetic predisposition - fair skin and white eyesm in those with a tendency to freckle and burn, with a history of burns
fair skin
older children and young adults - Children acquire more nevi as they grow older, with the peak for adults being in their third decade. Excludes congenital nevi
Ix for melanocytic naevi
dermatoscopy:
- patterns depend on type - generally show symmetrical structures and colours
- have 1 or 2 colours - reflect the location of the pigment in the skin
- black and brown = pigment in the epidermis
- grey and blue = pigment in the superficial and deep dermis respectively
- reticular pattern (grid of brown lines overlies a light brown background and globular pattern, with numerous brown, round-oval structures)
- cobblestone - variation of globular pattern, papillomatous or mammillated dermal nevus
- homogenous pigment (diffuse grey-blue to grey-black pigmentation w/o other patterns, blue naevi)
- starburst - pigmented streask in a radial arrangement of the edge, spitz naevi
- dysplastic or clark’s naevi - asymmetrical pink, brown and tan colouration - pigment network may be typical or atypical, with hypopigmented areas.
- A multi-component pattern is a combination of 3 or more patterns and may signify a higher possibility of melanoma.
- Nevi located on special sites exhibit distinctive clinical, dermatoscopic, and histopathological features of which the clinician should be aware. For example, nevi of the face may show a pseudo-network pattern secondary to prominent follicular units, and acral nevi exhibit a parallel furrow pattern in which pigment is accentuated in the narrow furrows of the dermatoglyphs. Age, skin type, ultraviolet light exposure, pregnancy, and growth dynamics also influence the dermatoscopic findings of melanocytic nevi.
mx of melanoma
excision biopsy
sentinal node mapping
isolated limb perfusiona nd block dissection of regional LN groups
