Dermatology Book

Atypical NevusAka: Atypical Nevi, Atypical Mole, Clark Nevus, FAM-M Syndrome, Dysplastic Nevus, Compound Nevus with Associated Architectural Disorder


  1. See Also
    1. Nevus
    2. Congenital Melanocytic Nevus (C1318558)
    3. Melanoma
    4. Melanoma Risk Factors
  2. Epidemiology
    1. Chest and back are most commonly involved
    2. Malignant Melanoma Incidence is increasing (approaches 3% lifetime risk)
      1. Maintain a higher level of suspicion
  3. Classification: Spectrum of Nevus findings
    1. Compound Nevus
    2. Compound Nevus with associated architectural disorder
      1. Mild cytologic atypia
      2. Severe cytologic atypia
    3. Atypical melanocytic hyperplasia (Melanoma in-situ)
    4. Melanoma
  4. Risk Factors: Correlation to Melanoma
    1. Small Nevi (2-5 mm)
      1. Under 25 small nevi: RR=1.0
      2. Over 100 small nevi: RR=3.1
    2. Larger Non-dysplastic nevi (>5 mm)
      1. Over 9 non-dysplastic nevi: RR=2.3
    3. Dysplastic nevi
      1. One dysplastic nevi: RR=2.2
      2. Over 9 dysplastic nevi: RR=12.0
    4. FAM-M Syndrome (50 atypical nevi and 2 family members with Melanoma)
      1. Cummulative 10 year risk of Melanoma exceeds 10%
      2. Cummulative lifetime risk of Melanoma approaches 100%
  5. Signs: Abnormal moles (Mnemonic: ABCDEFG)
    1. Asymmetry (non-geometric outline - i.e. not circular or eliptical)
    2. Border irregular or indistinct
    3. Color non-uniform (variable pigmentation)
    4. Diameter over 5 mm (pencil eraser size)
    5. Elevation
    6. Feeling or change in sensation
    7. Growth
  6. Diagnostics: Dermoscopy
    1. Handheld dermatoscope (10X magnifier) applied over pre-oiled skin
    2. Helps identify atypical nevus patterns (reticular, globular, homogenous)
    3. Online dermoscopy tutorial
  7. Protocol: Lesions to Act on (Biopsy or Refer):
    1. Very high risk patients without monitoring plan
      1. See Melanoma Risk Factors
      2. Annual skin exam
    2. Suspicious lesions ("ugly duckling sign" - one mole that stands out)
      1. Eroded, crusted, ulcerated or bleeding >3 weeks
      2. Translucent Papules with telangiectasia
      3. New mole after age 30 years
      4. Keratotic lesions on face, ears, lips or genitalia
        1. Not typical for Seborrheic Keratoses
      5. Asymmetric, irregularly bordered lesions (see signs above)
        1. Multicolored or irregularly pigmented
        2. Changing in size, shape, surface, or color
      6. Black lesions on non-sun exposed skin
        1. Persons with white or light tan colored skin
  8. Protocol: Lesions to Ignore (Reassure patient):
    1. Benign lesions
      1. Seborrheic Keratosis
      2. Dermatofibroma
      3. Dermal Nevus
      4. Cherry Angioma
      5. Freckle
      6. Lentigo
      7. Cafe-Au-Lait Spot
    2. Lesions present less than 3 weeks
    3. Lesions <3mm, macular, and without change
    4. Lesions <6mm without change and no act on criteria
  9. Protocol: Lesions to Watch (Reevaluate at 2 and 6 months):
    1. All lesions not classified as Ignore or Act on
  10. Precautions
    1. Excisional Biopsy with 2 mm margin is preferred
    2. Reexcise lesions if moderate or severe cytologic atypia on biopsy and positive margins
      1. Margins should be at least 2 mm (5 mm if severe atypia)
    3. Do not Shave Biopsy any lesion suspected of Melanoma
      1. Full thickness specimen is critical
  11. Reference
    1. Cyr (2008) Am Fam Physician 78(6):735
    2. Naeyaert (2003) N Engl J Med 349:2233
    3. Tucker (1997) JAMA 277:1439
    4. Weinstock (1996) J Am Acad Dermatol 34(6):1063

Dysplastic Nevus (C0205748)

Definition (NCI)(dis-PLAS-tik NEE-vus) An atypical mole; a mole whose appearance is different from that of a common mole. A dysplastic nevus is generally larger than an ordinary mole and has irregular and indistinct borders. Its color frequently is not uniform and ranges from pink to dark brown; it is usually flat, but parts may be raised above the skin surface.
Definition (NCI)(dis-PLAS-tik NEE-vye) Atypical moles; moles whose appearance is different from that of common moles. Dysplastic nevi are generally larger than ordinary moles and have irregular and indistinct borders. Their color frequently is not uniform and ranges from pink to dark brown; they usually are flat, but parts may be raised above the skin surface.
Definition (NCI)Solitary or multiple, slightly raised, pigmented lesions with irregular borders, usually measuring more than 0.6cm in greatest dimension. Morphologically, there is melanocytic atypia and the differential diagnosis from melanoma may be difficult. Patients are at an increased risk for the development of melanoma.
ConceptsNeoplastic Process (T191)
EnglishAtypical naevus, Atypical naevus of skin, Atypical nevus, Atypical nevus of skin, Clark's Nevus, DN - Dysplastic naevus, DN - Dysplastic nevus, Dysplastic naevus, Dysplastic naevus of skin, Dysplastic Nevi, Dysplastic Nevus, Dysplastic nevus of skin, Lentiginous Nevus, NAD, Nevus with Architectural Disorder and Cytologic Atypia of Melanocytes
Spanishnevo atipico, nevo cutaneo atipico, nevo cutaneo displasico, nevo displasico
Parent ConceptsMelanocytic nevus (C0027962), Melanocytic tumor of skin (C0349501), Cutaneous Precancerous Condition (C0877510), Benign neoplasm of skin (C0004998), Acquired melanocytic nevus (C1302707), Duplicate concept (C1274013)
Derived from the NIH UMLS (Unified Medical Language System)

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