Nevi and Melanoma - Fisher Flashcards
what cell type are melanocytes derived from?
neural crest cells
where can melanoma and nevi occur?
anywhere neural crest cells migrate
where is the most common site for melanoma formation histologically?
dermal-epidermal junction
What are the 5 general criteria for a gross diagnosis of melanoma?
A - asymmetry B - irregular borders C - color variation D - large diameter E - evolving/ elevated
what is the most important factor contributing to melanoma prognosis
ulceration and depth of dermal involvement
what do nevi and melanoma have in common?
both comprised of melanocytes, both can share mutations such as BRAF
in general, are nevi pre-melanomas? what percentage of melanomas are derived from nevi?
no only 20% of melanoma develop from nevi
how are nevi related to risk of melanoma
an increased number of nevi (more than 50) increase risk of melanoma
what are the 3 types of acquired melanocytic nevi?
junctional, compound, intradermal
What is this? and define
junctional nevus - nests of melanocytes are present within epidermis only
what is this? and define
compound nevus - nests of melanocytes are present within epidermis and dermis
what is this? and define
Intradermal nevus - nest of mealnocytes within dermis only
what is the classic definition of nevus?
any congenital lesion of the skin - a birthmark
2-3 mm in diameter, deeply pigmented and macular, arising at the dermal-epidermal junction above the BM - what type of nevus?
junctional
3-4 mm, slightly raised, moderately pigmented, melanocytes found both intradermally and dermally - what type of nevus
compound
large and dome shaped lesion, cells exclusively in the dermis - what type of nevus
dermal
define halo nevi. what pt population is it more common in?
common acquired nevus with a surrounding zone of depigmentation common in 1st 3 decades of life, equal in males and females, more common in patients w/ vitiligo, familial tendency
what is the etiology of halo nevi
highlights the relationship between melanocytic neoplasia and host immunity - body recognizes somewhere there is melanoma, starts attacking all nevi everywhere - causes clearing
how do you classify congenital nevi?
according to size (small less than 1.5 cm, medium 1.5-20 cm, large more than 20 cm)
congenital nevi classified according to size - how do you apply this classification to children
the number cutoffs are for adults; must adjust these numbers for neonate (know this)
describe the clinical features of a congenital nevus
pigmentation varying from brown to black, grossly irregular surface, and hypertrichosis (hair is a key finding)