Pathology of Pigmented Lesions Flashcards
where are melanocytes derived from?
neural crest
where do melanoblast migrate in embryogenesis?
skin
uveal tract
leptomeninges
what determines balance of pigment in skin and hair?
MC1R (melanocortin 1 receptor) gene
what hair colour would you have if you had phaeomelanin?
red
what hair colour would you have if you had eumelanin?
anything other than red
what does 1 defective copy of MC1R cause?
freckling
what does 2 defective copies cause?
freckling and red hair
what are lentigines?
age spots related to UV exposure
can melanocytic naevi be congenital
yes
how are naevi formed?
in infancy the melanocytes:keratinocytes ratio breaks down at various sites
what is a junctional naevus?
melanocytes proliferating at the DEJ causing naevus in childhood
what is a compound naevus
clusters from junctional naevus joining groups of cells in the dermis forming a new naevus; usually in adolescence
what is an intradermal naevus
only melanocytic activity is dermal causing a naevus
typical size of a dysplastic naevus?
> 5mm
where do blue naevi exist?
dermis
what do blue naevi contain?
dendritic spindle cells
who tends to get spitz naevi?
people under 20
what do spitz naevi look like?
well vascularised melanoma-like naevus
what does a spitz naevus look like on the microscope
epidermal hyperplasia
which gender gets malignant melanomas more commonly?
females
name 4 main types of melanoma`
superficial spreading
acral/mucosal lentiginous
lentigo maligna
nodular
which type of melanoma can metastasise?
VGP (vertical growth phase) melanomas i.e nodular
what happens in resting growth phase?
melanoma grows as macules
what happens in vertical growth phase?
melanoma cells invade the dermis forming an expansile mass with mitoses
what types of melanoma have to have RGP before they start VGP?
superficial spreading (SS)
acral/mucosal lentiginous (A/MLM)
lentigo maligna
what type of melanoma only grows by VGP?
nodular melanoma
What is Breslow depth?
The deepest (in mm) a melanoma tumour invades from the granular layer
when would melanoma survival half according to breslow’s depth?
2-4mm
what characteristics of a melanoma would affect overall prognosis?
ulceration metastasis fast mitotic rate LN invasion satellite lesions
melanoma treatment?
excision
lymphadenectomy if needed
why do blue naevi arise?
failure of complete migration of melanocytes
