II. Epidemiology
- Onset after childhood (contrast with common nevi)
- Atypical Nevi have onset at Puberty
- Atypical Nevi continue to form and develop until age 40-50 years
- Chest and back are most commonly involved in men
- Legs are most commonly affected in women
- Malignant melanoma Incidence is increasing (approaches 3% lifetime risk)
- Maintain a higher level of suspicion
- Atypical Nevus Prevalence
- Fair skin: 2-8%
- Skin of Color: <2%
III. Classification: Spectrum of Nevus findings
- Compound Nevus
- Compound Nevus with Associated Architectural Disorder
- Mild cytologic atypia
- Severe cytologic atypia
- Atypical melanocytic hyperplasia (Melanoma in-situ)
- Melanoma
IV. Risk Factors: Correlation to Melanoma
- See Melanoma Risk Factors
- Lifetime risk of Melanoma in caucusians: 0.8%
- Small Nevi (2-5 mm)
- Under 25 small nevi: RR=1.0
- Over 100 small nevi: RR=3.1
- Larger Non-Dysplastic Nevi (>5 mm)
- Over 9 non-Dysplastic Nevi: RR=2.3
- Dysplastic Nevi
- One Dysplastic Nevi: RR=2.2
- Over 9 Dysplastic Nevi: RR=12.0
- Atypical Moles and lifetime risk of Melanoma
- Atypical Moles and no Family HistoryMelanoma: 6%
- Atypical Moles and prior Melanoma: 10% (risk of second Melanoma)
- Atypical Mole Syndrome (FAM-M Syndrome, B-K Mole Syndrome)
V. Signs: Abnormal moles (Mnemonic: ABCDE)
- Asymmetry
- Non-geometric outline - i.e. not circular or eliptical
- One half of lesion differs from the other side
- Border irregular or indistinct
- Color non-uniform
- Variable pigmentation involving at least 2 different colors
- Diameter over 5-6 mm
- Pencil eraser size
- Evolution of lesion
- Recent change in mole size or features
VI. Signs: Other Abnormal Findings
- See Weighted Glasgow 7-point Checklist for Melanoma
- Associated itch or altered Sensation
- Inflammation at lesion site
- Oozing or crusting lesions
- New elevated or thickened lesion
- Firmness on palpation
- Ugly duckling size
- One lesion distinctly different than others
- Atypical Nevi are flat, but may have raised center (fried-egg sign)
VII. Signs: Distribution
- Common nevi
- Above the waist
- Sun exposed areas
- Atypical Nevi
- Back (most common)
- Arms and legs
- Area typically shielded from the sun
- Female Breast
- Scalp
- Buttock
- Groin
VIII. Diagnostics
-
Dermoscopy
- See Dermoscopy
- Handheld dermatoscope (10X magnifier) applied over pre-oiled skin
- Helps identify Atypical Nevus patterns (reticular, globular, homogenous)
- Significantly increases melanoma Test Sensitivity (from 76 to 92%) and Test Specificity (from 75 to 95%)
- Online Dermoscopy learning resources
-
Pigmented Lesion Assay (Dermtech PLA, Tape Strip Melanoma Detection)
- See Tape Strip Melanoma Detection
- Consider for Atypical Nevus in adults with Adults with Fitzpatrick Skin Type 1-3 (white)
- Avoid in highly suspicious lesions (biopsy instead), Psoriasis, Eczema, Skin Ulcers, bleeding or scarring
- Also avoid for lesions on palms, soles, nails, mucous membranes, hairy areas
- Adhesive sticker is applied to the entire surface of a suspicious pigmented skin lesion 5 to 16 mm
- Skin cells adhere to adhesive sticker, that is removed and submitted for analysis
- Dermtech PLA targets Melanoma genome markers in RNA (LINC00518, PRAME) with or without DNA (TERT)
- Biopsy is recommended when a positive marker is identified
- Efficacy
- Test Sensitivity 73.7% (NPV 98.6%, LR- 0.3)
- Test Specificity 89% (PPV 25%, LR+ 7.1)
- References
- Espinosa (2024) AM Fam Physician 109(3): 277-8
- Thomsen (2023) Skin Res Technol 29(3):e13286 +PMID: 36973976 [PubMed]
IX. Labs: Histology
- Atypical Melanocytes with large hyperchromatic nucleus
- Melanocytes collect in nests or groups
- Lymphocyte infiltration (patchy)
- Concentric Eosinophilic fibroplasia
X. Protocol: Lesions to Act on (Biopsy or Refer)
- Very high risk patients without monitoring plan
- See Melanoma Risk Factors
- Annual skin exam
- Suspicious lesions ("ugly duckling sign" - one mole that stands out)
- Eroded, crusted, ulcerated or bleeding >3 weeks
- Translucent Papules with Telangiectasia
- New mole after age 30 years
- Keratotic lesions on face, ears, lips or genitalia
- Not typical for Seborrheic Keratoses
- Asymmetric, irregularly bordered lesions (see signs above)
- Multicolored or irregularly pigmented
- Changing in size, shape, surface, or color
- Black lesions on non-sun exposed skin
- Persons with white or light tan colored skin
XI. Protocol: Lesions to Ignore (Reassure patient)
- Benign lesions
- Lesions present less than 3 weeks
- Lesions <3mm, Macular, and without change
- Lesions <6mm without change and no act on criteria
XII. Protocol: Lesions to Watch (Reevaluate at 2 and 6 months)
- All lesions not classified as Ignore or Act on
XIII. Precautions
- Biopsy all suspicious pigmented lesions (and take images for EMR prior to biopsy)
- Obtain full thickness sample with 1-3 mm margins
- Obtain Punch Biopsy, Fusiform Excision or deep saucerization
- Do not Shave Biopsy any lesion suspected of Melanoma
- Allows for Breslow Depth measurement (maximal thickness of primary lesion rounded to nearest 0.1 mm)
- Document dimensions at time of biopsy and photograph
- Original lesion size
- Surgical margin
- Residual lesion size
- Reexcise lesions if moderate or severe cytologic atypia on biopsy and positive margins
- Margins should be at least 2 mm for moderate dysplasia (5 mm if severe atypia)
- Pseudo-Melanoma
- Re-excision of previously excised nevi may give False Positive appearance of Melanoma to pathologist
- Alert pathologists when submitting a sample from a previously biopsied site
XIV. References
- Habif (2003) Clinical Dermatology, 4th ed.. Mosby, p. 773-813
- Cyr (2008) Am Fam Physician 78(6):735-42 [PubMed]
- Naeyaert (2003) N Engl J Med 349:2233-40 [PubMed]
- Perkins (2015) Am Fam Physician 91(11): 762-7 [PubMed]
- Tucker (1997) JAMA 277:1439-44 [PubMed]
- Weinstock (1996) J Am Acad Dermatol 34(6): 1063-6 [PubMed]
- Shenenberger (2012) Am Fam Physician 85(2): 161-8 [PubMed]