Pigmented Lesions Flashcards
(45 cards)
What percentage of the cells in the basal layer are melanocytes?
5-10%
Describe how melanocytes form
- Epidermal melanocytes originate in the neural crest
- As a foetus, the melanocyte migrates from the neural crest to the dermo-epidermal junction.
- They reside as a single cells in the basal layer.
How is skin colour controlled?
Dark skinned individuals do not have more melanocytes.
They have more melanosomes.
Melanosomes are secreted by melanocytes into surrounding keratinocytes.
At what stage of life do the number of moles sharply increase?
Puberty
What is a junctional melanocytic naevus?
A mole that is confined to the dermoepidermal junction
Over time, naevus cells can extend into the dermis.
What is this called?
A compound naevus
Over more time, melanocytic cells can migrate fully into the dermis.
What is this called?
Intradermal naevus.
(All the junctional components have been lost)
What is this?
An intradermal naevus
- No pigment
- Papillomatousnodules.
Is this a Junctional Naevus or a Compound Naevus?
Compound Naevus
- Usually raised.
- Colours vary
- Sometimes hyperkeratotic
What is a CMN?
Congenital Melanocytic naevi
(Think Birthmark)
How are congenital naevi classified?
(According to size)
- small CMN = <1.5 cm diameter
- medium CMN = 1.5 - 19.9 cm diameter
- large or giant CMN = 20 cm or more in diameter
Why do Giant Congenital Melanocytic Naevi need to be monitored?
They have a 30% chance of malignancy
What are the other benign naevi to be aware of apart from CMN?
- Spitz naevus
- Halo naevus
- Becker’s naevus
- Blue Naevus
What is this?
When & Where does it occur?
How do you treat it?
Spitz Naevus
- It usually grows rapidly on the face of a child
- Reaches 1-2 cm and then stops.
- AKA Juvenile Melanoma - but is benign
- Best to excise as it is difficultto differentiate from a melanoma
What is this?
Halo Naevi
- Occurs on the trunk of children or adolescents
- The body’s immune system is destroying the naevus cells.
What is this?
Becker’s naevus
- Becomes darker and hairy after puberty
- More common in adolescent males
- No effective treatment
What benign naevus is this?
A Blue Naevus
- Deep dermal collection of melanocytes.
- As they migrate from the neural crest to the epidermis during foetal life they stop in the dermis rather than the dermalepidermal junction
- Usually occur on the scalp, face, hands and feet.
What are the characteristics of an atypical mole?
- >5mm
- Irregular shape
- Smudged border
- Irregular pigmentation +/- erythema
- Papular + Macular component.
What % of the population have Atypical Mole Syndrome?
What is their risk of developing melanoma?
1-5% of the population
10x risk of melanoma
What is FAMM syndrome?
Familial Atypical Multiple Mole-Melanoma Syndrome
- Mutation in the CDKN2A or CDK4 gene
- Associated with pancreatic cancer.
- 400x increase in melanoma risk if 1st and 2nd degree relatives have atpyical naevi + melanomas.
What % of melanomas arise melanocytic naevi?
30%
What factors lead to an increased risk of melanoma?
- Sun exposure
- Skin type
- Large numbers ofmelanocytic naevi
- Large CNS
- Family history
- Personal history
- Immunosuppresion.
Describe the cellular pathway whereby melanomas form?
40-60% of melanomas result from a BRAF mutation.
This leads to MEK & ERK phosphorylationand cell proliferation.
This is independent of extracellular growth factors.
Describe the ABCDE Rule
- Asymmetry
- Border irregularity
- Colour irregular/variable pigmentation
- Diameter >6 mm (not always helpful)
- Elevation / Enlargement / Evolution– any mole which clearly changes over weeks to months
