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dysplastic (Clark's) melanocytic nevus
Premalignant lesions.
Etiology:
1) most dysplastic melanocytic nevi arise in contiguity with a compound melanocytic nevus
2) abnormal clones of melanocytes may be activated by exposure to light
Epidemiology:
1) 5% of white population
2) occurs in all patients with familial cutaneous melanoma
3) occurs in 30-50% with sporadic nonfamilial melanoma
4) white population, no data on blacks, rare in Japanese
5) occurs in children & adults
6) no sex preference
Genetics:
1) sporadic or autosomal dominant dysplastic nevus syndrome
2) chromosomal aberrations 1p36 & 9p21
Pathology:
1) hyperplasia & proliferation of melanocytes in the basal cell layer either as spindle cells or epithelioid cells
2) irregular & dyshesive nests of melanocytes
3) melanocytes are atypical
a) larger than normal
b) pleomorphic nuclei & cell bodies
c) hyperchromatic nuclei
4) bridging between rete ridges by melanocytic nests
5) spindle-cell melanocytes oriented parallel to skin surface
6) lamellar fibroplasia & concentric eosinophilic fibrosis may be present
7) proliferation of blood vessels may occur
8) a sparse to dense lymphocytic infiltrate may occur
Clinical manifestations:
1) 5-10 mm or larger macules or papules; commonly > 6 mm (> 5 mm) [2]
2) generally on trunk & limbs, may occur in areas not exposed to sunlight
3) variegated in color within lesion; pink, tan, brown; lesions may be black [3]
4) asymmetric shape with irregular border & surface [3]
5) 'fried egg' appearance with darker, elevated central portion & tan, flat edges blending into the surroundings [3]
6) lesions 1st appear in late childhood, just before puberty
7) new lesions continue to develop over many years
8) lesions rarely undergo spontaneous regression
9) generally asymptomatic
10) imunosuppressed patients with dsyplastic nevi have a higher incidence of melanoma
* images [6,7]
Laboratory:
1) Wood's lamp examination will markedly accentuate the epidermal hyperpigmentation of lesions
2) epiluminescence microscopy
Differential diagnosis:
1) congenital melanocytic nevus
2) common acquired melanocytic nevus
3) superficial spreading malignant melanoma
4) melanoma in situ
5) lentigo maligna
6) Spitz nevus
7) pigmented basal cell carcinoma
8) seborrheic keratosis
Complications:
- increased risk of melanoma
a) general population - 0.8%
b) familial dysplastic nevi - 100%
c) dysplastic melanocytic nevi - 18%
- most melanomas that arise in patients with dysplastic nevi develop on the intervening 'normal' skin [3]
Management:
1) surgical excision of lesions with minimal margins sent for pathology
- selection of lesions
- lesions that are changing in size, shape or color
- lesions not easily amenable to self-examination by the patient (scalp, genitalia, back)
- a single, atypical dysplastic nevus [3]
- symptomatic nevi
- other lesions should be observed [3]
2) lasers or other destructive modalities should not be used because they interfere with histologic diagnosis
3) follow-up
- every 3 months for patients with familial dysplastic nevi
- every 6 months for patients with sporadic dysplastic nevi
4) patient education
- avoid the sun
- use sunscreen, clothing
- self exam
- illustrative patient informatation depicting dysplastic nevi
5) examine family members
6) referral to dermatology [3]
Related
basal cell carcinoma (BCC)
congenital melanocytic nevus
dysplastic nevus syndrome (inherited familial atypical mole & melanoma syndrome)
lentigo maligna
Spitz nevus; spindle cell nevus; epithelioid nevus
superficial spreading melanoma
General
genetic disease of the skin (genodermatosis)
melanocytic nevus (mole)
References
- Saunders Manual of Medical Practice, Rakel (ed), WB Saunders,
Philadelphia, 1996, pg 960-61
- Color Atlas and Synopsis of Clinical Dermatology, Common
and Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY,
1997, pg 182-86
- Medical Knowledge Self Assessment Program (MKSAP) 14, 16, 17, 18.
American College of Physicians, Philadelphia 2006, 2012, 2015, 2018.
- Medical Knowledge Self Assessment Program (MKSAP) 19
Board Basics. An Enhancement to MKSAP19.
American College of Physicians, Philadelphia 2022
- Naeyaert JM, Brochez L.
Clinical practice. Dysplastic nevi.
N Engl J Med. 2003 Dec 4;349(23):2233-40.
PMID: 14657431
- Duffy K, Grossman D.
The dysplastic nevus: from historical perspective to management
in the modern era: part II. Molecular aspects and clinical
management.
J Am Acad Dermatol. 2012 Jul;67(1):19.e1-12
PMID: 22703916
- Skin Cancer Foundation (images)
Dysplastic Nevi (Atypical Moles)
http://www.skincancer.org/skin-cancer-information/dysplastic-nevi
- Dysplastic Nevi - Warning signs and Images
http://www.skincancer.org/skin-cancer-information/dysplastic-nevi/dysplastic-nevi-warning-signs-and-images#panel1-1
- DermNet NZ. Atypical naevi (images)
http://www.dermnetnz.org/lesions/atypical-naevi.html
- What You Need To Know About Moles and Dysplastic Nevi
http://www.cancer.gov/templates/doc.aspx?viewid=c3508072-3797-40c7-848b-7bbbe9ce16d4