Pigmented Skin Lesions Flashcards
describe what melanocytes do during embryogenesis
derived from the neural crest, early in embryogenesis melanoblasts migrate to skin, uveal tract and leptominges - when they settle in the skin they form melanocytes. basally situated
does the melanocyte to keratinocyte ratio change depending on race
no
melanocytes
pigment producing dendritic cells
melanocyte role with UV radiation
protect DNA from UV radiation - convert tyrosine to melanin which absorbs light and form a protective cap over nucleus
what does non cancerous growth of melanocytes result in
moles and freckles
what gene determines the balance of pigment in skin and hair
MC1R
eumelanin causes what hair colour
everything but red
phaeomelanin causes what hair colour
ed
MC1R role
convert phaeomelanin to eumelanin
determines the balance of pigment in skin and hair
one defective copy of MC1R
freckles
two defective copies of MC1R
red hair
another name for freckles
ephilides
what is a freckle
a patchy inc in melanin pigment that occurs after UV exposure
actinic/solar lentigines
also known as liver/age spots found on face, forearms and dorsal aspects of the hands
actinic/solar lentigines histological features
epidermis elongated rete ridges and increase in melanin and basal melanocytes
another name for mole
- melanocytic naevi
size of small mole
<2cm diameter
size of medium mole
>2 and <20 cm
what risk do large moles have
risk of melanoma - surgical excision
usual type acquired naevi
A melanocyte proliferation (breakdown of the melanocytes:keratinocytes ratio) which arises in the epidermis and then spreads to the dermis.
Within time the epidermal component, and subsequently the entire naevus disappears.
histological features of usual type acquired naevi
epidermis shows lengthening of rete ridges and slight hyperkeratosis
3 phases of naevi
junctional compound intradermal
junctional phase
naevi arise from epidermal melanocytes, situated at DEJ, these proliferate and form cell nests
compound phase
naevus extend into superficial dermus (clinically innocent phenomenon) involve both junction and dermis proper
intradermal phase
junctional component disappears in adulthood so all naevus cells are now intradermal
dysplastic naevi size
generally >6mm diameter
dysplastic naevi
varied pigment and border asymmetry - some hallmarks of melanoma but not enough to be classified as malignant
host reaction fibrosis and inflammation occurs
how do dysplastic naevi occur
sporadically or familial
what is the risk of melanoma with familial dysplastic naevi
lifetime risk up to 100% high penetrance (CDKN2A)
halo naevi
peripheral halo of depigmentation due to loss of melanocytes from lymphocyte action
blue naevi - dermal/epidermal involvement
entirely dermal
blue naevi
uniform and structureless
consist of pigment rich dendritic spindle cells
spitz naevus presentation
symmetrical reddish or skin coloured nodule
spitz naevus
nest of spindle shaped melanocytes most are entirely benign but there is a malignant variant
why are spitz naevus pink
due to prominent vasculature
what cells do melanomas arise from
melanocytes which are found along the basal layer of the epidermis
what is the 5 year survival rate for melanoma if confined to epidermis
95-100% (<1mm) cannot reach blood supply
what is the 5 year survival rate for melanoma if entered the dermis
50%
what is the 5 year survival rate for melanoma if it has metastasised
5%
ABCDE rule
asymmetry, border, colour, diameter and evolution
what is the ugly duckling sign
way to identify if any mole stands out from the rest
where can superficial spreading melanomas occur
anywhere
superficial spreading melanoma features
most common type, irregular shape, flat periphery and slow growing
grow laterally before vertical invasion
where can nodular melanomas be found
anywhere
nodular melanoma
Most aggressive type, grows rapidly from the start.
Presents as rapidly growing pigmented nodule which bleeds or ulcerates.
where can Acral/Mucosal Lentiginous Melanoma be found
on the nails, soles of feet or palms of hands
may not be related to sun exposure
who is Acral/Mucosal Lentiginous Melanoma most common in
coloured races
where does lentigo maligna melanoma occur
sun damaged face/neck/scalp in old people
what is the precursor lesion for lentigo maligna melanoma
lentigo maligna (Hutchinson’s freckle) - a slow growing macular area of pigmentation seen in elderly people, commonly on the face.
confined to epidermis (in situ)
diagnosed as lentigo maligna melanoma when the malignant melanoma has invaded the dermis
what is the prognosis of melanoma related to
Breslow depth and ulceration
what is breslow depth
deepest tumour measured from the granular layer down in mm
what does the suffix B when describing tumour staging refer to
ulceration - worse prognosis
what stain is used to determine lymph node involvement
S100
what can acral melanomas with c-kit mutation be treated with
imatinib
what mutation may melanomas on intermittently sun exposed skin have
BRAF mutation
what is the role of BRAF
proto-oncogene that stimulates the MAPKK pathway stimulating cell division. The mutated form becomes a potent oncogene that drives cell division
what drugs interfere with the BRAF MAPKK pathway
eg dabrafenib and vemurafenib
spitz naevus
superficial spreading melanoma
lentigo maligna melanoma
halo naevi
dysplastic naevi
dysplastic naevi
melanoma arising in a dysplastic naevi
what is this naevi
junctional
what is this naevi
intradermal
what is this naevi
compound
