pigmented lesions Flashcards
where are melanocytes derived from?
neural crest
where do melanoblasts migrate to early in embryogenesis?
skin
uveal tract
leptomeninges
when do melanoblasts form melanocytes?
once settled in the skin
what is melanocortin 1 receptor gene?
encodes MC1R protein-sits on cell surface
determines balance of pigment in skin and hair
what does eumelanin responsible for?
all hair colours except red
what does phaeomelanin cause?
red hair
what does MC1R do?
turns phaeomelanin into eumelanin
what does 1 defective copy of MC1R cause?
frecklesw
what does 2 defective copies of MC1R cause?
red hair and freckles
what do freckles (ephilides) reflect?
clumpy distribution of melanocytes
what are actinic lentigines related to?
UV exposure and increase melanin and basal melanocytes
where are actinic lentigines usually seen?
face
forearms
dorsal hands
what allows for the formation of simple naevi?
during infancy the melanocytes to keratinocyte ratio breaks down at a number of cutaneous sites
what are the characteristics of dysplastic naevi?
> 6mm diameter
variated pigment
border asymmetry
what are the characteristics of sporadic DN?
not inherited
one to several atypical naevi
risk of MM raised
what are the characteristics of familial DN?
strong FHx of melanoma
autosomal inheritance
high penetrance
many atypical naevi
risk of melanoma hella high
which layer of the skin isn’t affected by DN?
epidermis
what are halo-naevi?
peripheral halo of depigmentation
show inflammatory regression
overrun by lymphocytes
what are blue naevi?
entirely dermal
consist of pigment rich dendritic spindle cells
cellular variant may have mitoses and mimic melanoma
what are the characteristics of spitz naevi?
very rare
<20 y/o
large spindle and/or epithelioid cells
mimic melanoma
most are benign
pink colouration (prominent vasculature)
where are melanoma most commonly found?
sun exposed areas
scalp, face, neck, arm, trunk, leg
what is the main cause of malignant melanoma?
UV exposure
what are the features that would make you sus of malignant melanoma?
new pigmented lesion develops in adulthood
ulceration
development of satellite nodules
bleeding
irregular pigmentation
change in shape
what are the 4 main types of melanoma and where are they commonly found?
superficial spreading - trunk and limbs
acral/mucosal lentiginous - acral and mucosal
lentigo maligna - sun damaged face/neck/scalp
nodular - varied, mainly trunk
what are the features of SSM, A/MLM and LMM?
grow as macules either entirely in-situ or with dermal microinvasion (RGP)
eventually melanoma cells invade the dermis forming an expansile mass with mitosis (VGP)
only RGP or VGP can metastasise?
VGP
what type of tumour is a nodular melanoma?
simple nodule of VGP tumour
what does the prognosis of melanoma relate to?
breslow thickness
what are other prognostic indicators?
ulceration
suffix b = tumour ulceration
high mitotic rate, lymphovascular invasion, satellites, sentinel lymph node involvement
how can malignant melanoma spread?
local dermal lymphatics -> satellite deposits of MM
regional lymph node metastases - common patterns of disease progression (nodes excised)
blood spread - skin/soft tissue, heart, lungs, GI tract, liver, brain
how is melanoma treated?
primary excision = to give clear margins
some receive sentinel node biopsy
SN positive = regional lymphadenectomy
what is used to treat advanced disease?
chemo
immunotherapy
genetic therapies
what is the clearance if invasive but <1mm?
1cm clearance
what is the clearance if invasive and >1mm?
2cm
what is BRAF?
a weak cytosolic proto-oncogene
what happens if BRAF is mutated
drives cell proliferation by up-regulating MEK and ERK
