Benign and malignant melanocytic lesions Flashcards
What is the single most important risk factor for melanoma?
UV exposure
- episodes of sunburn
Risk factors for melanoma?
- FH
- previous melanoma
- severe sunburn in childhood
- increased UV exposue
- atypical moles (multiple dysplastic naevi)
- large congenital naeve
Where are melanocytes found?
Basal layer of epidermis
What are freckles?
increased number of melanocytes (increase in UV exposure)
What is a mole made up of?
nest of melanocytes
What is a junctional naevus and what does it look like?
acquired moles in late childhood/early adolescence
flat and dark
What is a compound naevus and what does it look like?
The nests migrate deeper into the dermis, so the melanocytes are in the dermis and epidermis
Dome shaped brown papule
What is an intradermal naevus?
Dome shape skin coloured, when it goes further into dermis
What are the stages in the evolution of a mole?
- junctional naevus
- compound naevus
- intradermal naevus
What are atypical naevi?
Atypical mole, looks like a melanoma but benign
Can be asymmetrical, large and different colours
Often excised as cannot distinguish
Aetiology of atypical moles?
- genetic
- childhood sun exposure
Prevalence of atypical moles?
2-5%
Risk of atypical moles?
high risk of getting melanoma esp if >50 or with family history
2 other types of acquired naevi?
- halo naevus
- blue naevus
What is a congenital naevus?
Present from birth
Less common than acquired
Can vary in size
What is the 7 point checklist for a melanoma?
Major features:
- changing colour
- changing size
- changing size
Minor features:
- bleeding
- inflammation
- itching
- > 7mm in size
How do we describe a melanoma?
Asymmetry Border Colour Diameter Elevation
Different types of melanona?
In situ melanoma: - lentigo maligna - melanoma in situ Invasive melanoma - superficial spreading - nodular melanoma - lentigo maligna - acral melanoma
What is a lentigo maligna?
- malignant cells confined to epidermis
- sun exposure sites
- v long hx of increased size, change in shape and colour
- often starts as a large freckle (lentigo)
- can become malignant if not treated
Most common type of invasive melanoma?
- superficial spreading - 70%
- thin and expands radically
What does a nodular melanoma look like and what is its prognosis?
- raised from the skin
- tends to be thick and invade vertically
- poorer prognosis
- rare
Which type of malignant invasive melanoma is more common in dark skin?
- acral melanoma
- invades rapidly
- Bob marley died of this!!!
What does the prognosis of melanoma depend on?
Depth of invasion - Breslow thickness 5 y survival - in situ 100% - <1mm 95% - 1-3mm 70% - >3mm 40% or less
Possible ddx of melanoma?
- seborrhoeic wart
- pigmented BCC
- dermatofibroma
- pyogenic granuloma
- atypical mole
- blue naevus
