Dysplastic Nevus

Atypical Nevus

Clark’s Nevus

 

Epidemiology:

    •  Lentiginous dysplastic nevus of the elderly:
      • >60y

 

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:

Sensitivity:

Specificity:

 

 

 

 

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:

    • Robbins 2005
    • Weedon 2002