II. Epidemiology

  1. Onset after childhood (contrast with common nevi)
    1. Atypical Nevi have onset at Puberty
    2. Atypical Nevi continue to form and develop until age 40-50 years
  2. Chest and back are most commonly involved in men
  3. Legs are most commonly affected in women
  4. Malignant melanoma Incidence is increasing (approaches 3% lifetime risk)
    1. Maintain a higher level of suspicion
  5. Atypical Nevus Prevalence
    1. Fair skin: 2-8%
    2. Skin of Color: <2%

III. 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

IV. Risk Factors: Correlation to Melanoma

  1. See Melanoma Risk Factors
  2. Lifetime risk of Melanoma in caucusians: 0.8%
  3. Small Nevi (2-5 mm)
    1. Under 25 small nevi: RR=1.0
    2. Over 100 small nevi: RR=3.1
  4. Larger Non-Dysplastic Nevi (>5 mm)
    1. Over 9 non-Dysplastic Nevi: RR=2.3
  5. Dysplastic Nevi
    1. One Dysplastic Nevi: RR=2.2
    2. Over 9 Dysplastic Nevi: RR=12.0
  6. Atypical Moles and lifetime risk of Melanoma
    1. Atypical Moles and no Family HistoryMelanoma: 6%
    2. Atypical Moles and prior Melanoma: 10% (risk of second Melanoma)
  7. Atypical Mole Syndrome (FAM-M Syndrome, B-K Mole Syndrome)
    1. Ten year risk of Melanoma exceeds 10%
    2. Lifetime risk of Melanoma approaches 100%

V. Signs: Abnormal moles (Mnemonic: ABCDE)

  1. Asymmetry
    1. Non-geometric outline - i.e. not circular or eliptical
    2. One half of lesion differs from the other side
  2. Border irregular or indistinct
  3. Color non-uniform
    1. Variable pigmentation involving at least 2 different colors
  4. Diameter over 5-6 mm
    1. Pencil eraser size
  5. Evolution of lesion
    1. Recent change in size or features

VI. Signs: Other Abnormal Findings

  1. Associated itch or altered Sensation
  2. Inflammation at lesion site
  3. Oozing or crusting lesions
  4. Ugly duckling size
    1. One lesion distinctly different than others
  5. Atypical Nevi are flat, but may have raised center (fried-egg sign)

VII. Signs: Distribution

  1. Common nevi
    1. Above the waist
    2. Sun exposed areas
  2. Atypical Nevi
    1. Back (most common)
    2. Arms and legs
    3. Area typically shielded from the sun
      1. Female Breast
      2. Scalp
      3. Buttock
      4. Groin

VIII. Diagnostics

  1. Dermoscopy
    1. See Dermoscopy
    2. Handheld dermatoscope (10X magnifier) applied over pre-oiled skin
    3. Helps identify Atypical Nevus patterns (reticular, globular, homogenous)
    4. Online Dermoscopy tutorial
      1. http://www.dermoscopy.org/atlas/base.htm
  2. Pigmented Lesion Assay (Dermtech PLA, Tape Strip Melanoma Detection)
    1. See Tape Strip Melanoma Detection
    2. Consider for Atypical Nevus in adults with Adults with Fitzpatrick Skin Type 1-3 (white)
    3. Avoid in highly suspicious lesions (biopsy instead), Psoriasis, Eczema, Skin Ulcers, bleeding or scarring
    4. Also avoid for lesions on palms, soles, nails, mucous membranes, hairy areas
    5. Adhesive sticker is applied to the entire surface of a suspicious pigmented skin lesion 5 to 16 mm
      1. Skin cells adhere to adhesive sticker, that is removed and submitted for analysis
      2. Dermtech PLA targets Melanoma genome markers in RNA (LINC00518, PRAME) with or without DNA (TERT)
      3. Biopsy is recommended when a positive marker is identified
    6. Efficacy
      1. Test Sensitivity 73.7% (NPV 98.6%, LR- 0.3)
      2. Test Specificity 89% (PPV 25%, LR+ 7.1)
    7. References
      1. Espinosa (2024) AM Fam Physician 109(3): 277-8
      2. Thomsen (2023) Skin Res Technol 29(3):e13286 +PMID: 36973976 [PubMed]

IX. Labs: Histology

  1. Atypical Melanocytes with large hyperchromatic nucleus
  2. Melanocytes collect in nests or groups
  3. Lymphocyte infiltration (patchy)
  4. Concentric Eosinophilic fibroplasia

X. 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

XI. 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

XII. Protocol: Lesions to Watch (Reevaluate at 2 and 6 months)

  1. All lesions not classified as Ignore or Act on

XIII. Precautions

  1. Biopsy pearls
    1. Full thickness specimen is critical
      1. Punch Biopsy, Excisional Biopsy or Saucerization Biopsy
      2. Do not Shave Biopsy any lesion suspected of Melanoma
    2. Excisional Biopsy with 2 mm margin is preferred
    3. Document dimensions at time of biopsy
      1. Original lesion size
      2. Surgical margin
      3. Residual lesion size
  2. Reexcise lesions if moderate or severe cytologic atypia on biopsy and positive margins
    1. Margins should be at least 2 mm for moderate dysplasia (5 mm if severe atypia)
  3. Pseudo-Melanoma
    1. Re-excision of previously excised nevi may give False Positive appearance of Melanoma to pathologist
    2. Alert pathologists when submitting a sample from a previously biopsied site

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