Dysplastic Nevus
Atypical Nevus
Clark’s Nevus
Epidemiology:
- Lentiginous
dysplastic nevus of the elderly:
Common sites:
- may occur in
non-sun exposed as well as sun-exposed sites
- trunk
- legs in females
- lentiginous
dysplastic nevus of the elderly:
- back in males
- legs in females
Gross features:
- >5mm often
- mixture of tan,
dark brown, and pink areas often
- various
appearances:
- flat macule
- “pebbly” plaque
- target-like, with
raised, hyperpigmented centre, and flat,
less pigmented periphery
- atypical nevus
syndrome:
- 80 or more nevi
- appear normal in
childhood, abnormal lesions appearing in adolescence and adult life
Histologic features:
- lentiginous
hyperplasia with junctional nest disarray:
- single and nests
of melanocytes along the basal layer
- may involve the
sides as well as the tips of the elongated rete ridges
- bridging of nests
- random cytological
atypia in junctional component:
- occasional cells
with enlarged, hyperchromatic nuclei
- nucleus equal or
larger than overlying keratinocytes
- sometimes
prominent nucleoli
- atypia graded into
low-grade and severe (not well standardized)
- alterations in
superficial dermis
- linear or
lamellar, concentric fibrosis in underlying superficial dermis
- patchy superficial
lymphocytic infiltrate
- pigment
incontinence
- architectural
atypia (shoulder phenomenon):
- peripheral
extension of the junctional component beyond the dermal component
- dermal component
usually present centrally
- small cells or
epithelioid cells
- only slight
maturation
- impairment of
pigment synthesis
- may show features
of other nevus varieties (congenital, Spitz, blue, halo, dermal
neuronevus)
- cells often show
shrinkage artifact
- scant cytoplasm
- spindle-shaped
pattern
- may see:
- larger cuboidal
(epithelioid) cells with dusty pigment
- lentiginous
dysplastic nevus of the elderly:
- elongated rete
ridges of uneven size and pattern
- extensive
junctional nesting as well as single melanocytes
- nests irregular
in size and distribution
- confluence of
melanocytes over occasional single suprapapillary plastes
- hyperchromatic
nuclei and focal atypia
- prominent
lamellar fibrosis around dermal papillae
- variable
lymphocytic infiltrate and pigment incontinence
- usually no dermal
component
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
- familial
melanoma:
- mutations in
CDKN2A gene (chromosome 9p21) have been found
Other features:
- most are clinically
stable, but may progress to melanoma
- associated with
heritable melanoma syndrome (familial) (dysplastic / atypical nevus syndrome)
(B-K mole syndrome) (FAMMM syndrome)
- melanoma – AD
inheritance with incomplete penetrance
- atypical nevus
- patients with
atypical nevi have a 10% or more chance of developing melanoma (baseline
0.6%)
- eruptive form
(rare)
- lentiginous
dysplastic nevus of the elderly:
- important
precursor of melanoma and melanoma in situ in the elderly
References: