Benign Skin Lesions Flashcards
Features of benign pigmented lesions
Well defined margin
Even pigmentation
Symmetrical
Consistent over time
Common name for ephelides
Freckles
What are ephelides
Patchy increase in melanin pigmentation which occurs after UV exposure
Who is most likely to have freckles
People with fair skin and red hair
Genetics of ephelides
One defective copy of MC1R gene
Common name for actinic lentigines
Age spots or liver spots
What are actinic lentigines associated with
Long term UV exposure
Where do actinic lentigines usually present
Face, forearms and dorsal hands
Histology of actinic lentigines (2)
Elongated rate ridges in the epidermis
Increase in melanin and basal melanocytes
Another name for melanocytic naevi
Moles
Naevi present in childhood
Junctional naevi
Naevi present in adolescence and early childhood
Compound naevus
What are Congenital melanocytic naevus
Visible pigmented proliferations in the skin that are present at birth
Junctional naevus
Naevus cells cluster in the dermoepidermal junction
What can larger congenital melanocytic naevi show
Hypertrichosis
What is hypertrichosis
Excessive hair growth
How do we acquire usual type naevi
During infancy the melanocyte: keratinocyte ratio breaks down at a number of cutaneous sites which allows the formation of simple naevi
Intradermal naevi
All Junctional activity has ceased, entirely dermal
Dysplastic naevi presentation
Generally >6 mm in diameter, with varied pigment and border asymmetry
What is the most common type of dysplastic naevi
Sporadic
Lifetime melanoma risk in a patient with genetic predisposition to developing dysplastic naevi
Up to 100%
Give an example of a gene which can cause predisposition to development of dysplastic naevi
CDKN2A
Histology of dysplastic naevi
Architectural atypical and cellular atypia with a host reaction of fibrosis and inflammation
Epidermis is NOT effaced
Halo naevi
Peripheral halo of depigmentation
