Module 20: Other Nevi (Recurrent, Halo, Targetoid, and Rare Variants)
1. Learning Objectives
After completing this module, the learner should be able to:
- Classify the "targetoid" nevi (halo nevi, cockade nevi, Meyerson nevi) and describe the concentric morphologic pattern that unifies this group.
- Describe the dermoscopic features of halo nevi and explain the immune-mediated mechanism underlying the depigmentation halo, including the expected temporal course of involution and re-pigmentation.
- Recognize Meyerson nevi dermoscopically and explain why the eczematous reaction does not significantly distort the underlying nevus architecture.
- Identify cockade nevi by their distinctive targetoid dermoscopic pattern (central papule, inner hypopigmented rim, outer pigmented rim) and state the typical patient demographic and body site.
- Differentiate recurrent nevi from recurrent melanoma using dermoscopic criteria (pigment confinement to scar, centrifugal growth pattern, contiguous pigmented structures) and clinical parameters (age, location, time to recurrence).
- Describe how lichen sclerosus (LS) alters the dermoscopic appearance of melanocytic nevi and explain why nevi arising within LS can simulate melanoma, including management strategies.
- Recognize balloon cell nevi (BCN) by the presence of aggregated white-to-yellow globules and differentiate these globules from milia-like cysts using polarization characteristics.
- Describe the dermoscopic features and clinical significance of epidermolysis bullosa (EB) nevi, including the overlap with melanoma features and the recommended monitoring strategy.
2. Prerequisites
- Module 01: Introduction and Principles of Dermoscopy -- Optical principles, polarized vs. nonpolarized dermoscopy, and equipment fundamentals are essential for understanding the polarization-dependent features discussed in this module (e.g., white globules in balloon cell nevi).
- Module 02: Histopathologic Correlations of Dermoscopic Structures -- Understanding the histopathologic basis of dermoscopic colors and structures (network, globules, dots, structureless areas, regression structures) is necessary to interpret the patterns described in each nevus variant.
- Module 15: Congenital Melanocytic Nevi -- Baseline knowledge of congenital nevus patterns provides context for understanding large atypical nevi in the EB setting.
- Module 16: Acquired Melanocytic Nevi -- The globular, reticular, and homogeneous patterns of common acquired nevi form the substrate upon which the "other nevi" in this module are recognized.
- Module 17: Intradermal Nevus -- Intradermal nevi frequently serve as the central nevus in halo nevi and cockade nevi.
- Module 18: Blue Nevi and Variants -- Combined nevi and blue nevus variants provide differential diagnosis context.
- Module 19: Spitz and Reed Nevi -- Spitzoid features can overlap with atypical findings in some special nevus variants discussed here.
3. Key Concepts
3.1 Targetoid Nevi -- Umbrella Category
"Targetoid" nevi represent a group of melanocytic nevi that share a concentric, ring-like or bull's-eye morphology. The literature groups three entities under this heading:
| Variant | Central Component | Surrounding Zone | Mechanism |
|---|---|---|---|
| Halo nevus (Sutton nevus) | Melanocytic nevus (globular or homogeneous) | Symmetric white structureless depigmentation halo | T-cell immune-mediated melanocyte destruction |
| Cockade nevus | Brown papule/macule (compound nevus) | Inner hypopigmented rim + outer pigmented rim | Histologic zonation: central compound nevus, peripheral nonpigmented junctional nevus |
| Meyerson nevus | Pre-existing melanocytic nevus | Eczematous reaction (erythema, scale, pruritus) | Spongiotic dermatitis with CD4+ lymphocytes and eosinophils |
3.2 Melanoma Simulators
Two nevus variants are specifically categorized as "melanoma simulators" due to their capacity to mimic melanoma clinically and/or dermoscopically:
- Recurrent nevi -- Proliferations of nevomelanocytes after partial surgical or traumatic removal; may clinically present as pseudomelanoma.
- Lichen sclerosus nevi -- Nevi arising within lichen sclerosus; the altered stroma and inflammatory milieu produce atypical dermoscopic features that can simulate a multicomponent pattern.
3.3 Other Uncommon Variants
- Balloon cell nevi (BCN) -- Rare nevi with dermal lobules of large multinucleated balloon cells (melanocytes with extensive vacuolated cytoplasm due to defective melanosome formation).
- Epidermolysis bullosa nevi (EB nevi) -- Large, asymmetric, irregularly pigmented nevi arising on sites of prior blisters in patients with inherited epidermolysis bullosa; frequently demonstrate dermoscopic overlap with melanoma.
3.4 Key Terminology Reference
| Term | Definition |
|---|---|
| Halo nevus / Sutton nevus / Leukoderma acquisitum centrifugum | Melanocytic nevus surrounded by a rim of depigmentation due to immune-mediated melanocyte destruction |
| Meyerson nevus / Eczematous nevus | Melanocytic nevus with superimposed eczematous (spongiotic) dermatitis |
| Cockade nevus | Targetoid nevus with central compound nevus, inner hypopigmented rim, and outer pigmented rim |
| Recurrent nevus / Pseudomelanoma | Proliferation of nevomelanocytes within a scar after incomplete surgical or traumatic removal of a nevus |
| Centrifugal growth pattern | Radial outward growth from a central point, with pigment arranged symmetrically |
| Lichen sclerosus (LS) | Chronic inflammatory dermatosis of unknown etiology, predilection for anogenital area, manifesting as white/ivory macules or patches |
| Balloon cell | Melanocyte with extensive pale-staining, vacuolated cytoplasm due to defective melanosome formation |
| Epidermolysis bullosa (EB) | Group of mechanobullous diseases from mutations in keratin proteins at the dermo-epidermal junction |
| EB nevi | Large atypical nevi arising at sites of prior blisters in patients with inherited EB |
| Porcelain white structureless area | Bright white, featureless area characteristic of lichen sclerosus |
| Serocrusts | Dried serous exudate on the skin surface |
4. Core Content
4.1 Targetoid Nevi
4.1.1 Halo Nevi (Sutton Nevi)
Clinical Overview
Halo nevi, also known as Sutton's nevi or leukoderma acquisitum centrifugum, were first described by Sutton in 1916. They are characterized by a rim or halo of depigmentation surrounding a melanocytic nevus. Key clinical features include:
- Demographics: Frequently seen on the trunk of children and young adults.
- Associations: May occur with or without a history of atopic dermatitis or autoimmune disorders, particularly vitiligo.
- Underlying nevus: Most frequently a globular or homogeneous compound or intradermal nevus.
- Mechanism: The depigmentation represents one pathway to the involution of nevi -- specifically, a T-cell immune-mediated process that targets melanocytes.
- Natural history: Halo nevi persist for an average of 8 years before re-pigmentation occurs. This long timeline is important for patient counseling and follow-up planning.
Dermoscopic Characteristics
- Halo nevi usually occur in nevi with a globular or homogeneous pattern.
- A symmetric white structureless area is seen surrounding the central nevus structures.
- The central nevus may show dots/globules, homogeneous tan pigmentation, and/or gray dots/granules (indicating regression).
- After complete involution of the nevus, a pink central area can be observed where the nevus once was.
Differential Diagnosis: Halo Nevus vs. Melanoma with Peripheral Depigmentation
Rarely, melanomas can display peripheral depigmentation. However, key distinguishing features help differentiate the two:
| Feature | Halo Nevus | Melanoma with Depigmentation |
|---|---|---|
| Central lesion pattern | Globular or homogeneous (benign pattern) | Multicomponent pattern with melanoma-specific structures |
| Halo symmetry | Symmetric, uniform distribution | Irregular, asymmetric, uneven distribution |
| Central structures | Dots/globules, homogeneous tan, gray granules | Atypical network, irregular dots/globules, blue-whitish veil, regression structures |
| Age/demographics | Children and young adults | Typically older adults |
Clinical Pearl: Always evaluate the central lesion's dermoscopic architecture. If the central nevus displays only benign structures (globular or homogeneous pattern), the halo is almost certainly benign. If melanoma-specific structures are present in the central lesion, excision is warranted regardless of the halo.
Clinical Scenario
A 12-year-old boy presents with a 6 mm brown papule on his upper back surrounded by a uniform white ring of depigmentation. Dermoscopy of the central nevus shows a globular pattern with evenly distributed brown globules and no melanoma-specific structures. The surrounding halo is symmetric and structureless white.
What is the diagnosis, and when would this presentation require excision?
Halo Nevus (Sutton Nevus)
The symmetric white depigmentation halo surrounding a nevus with a benign globular pattern is classic for a halo nevus. The critical assessment is of the central lesion: if it shows only benign structures (globular or homogeneous pattern), the halo is benign. Excision is warranted only if the central nevus displays melanoma-specific structures (atypical network, irregular dots/globules, blue-whitish veil, regression). Halo nevi persist for an average of 8 years before re-pigmentation occurs.
4.1.2 Meyerson Nevi (Eczematous Nevi)
Clinical Overview
Meyerson nevi, first described by Meyerson in 1971, are melanocytic nevi with a superimposed eczematous reaction. Key clinical features include:
- Demographics: Usually found on the trunk and upper extremities of young adults.
- Clinical presentation: Erythema, scale, and pruritus surrounding and overlying a pre-existing nevus.
- Natural history: The eczematous reaction usually resolves after a few weeks or months without affecting the dermoscopic architecture of the associated nevus.
- Histopathology: A nevus (frequently compound) without atypia, associated spongiosis, and a perivascular infiltrate composed of CD4+ lymphocytes with occasional eosinophils.
- Treatment: Can be treated with topical corticosteroids to hasten resolution of the eczematous component.
Dermoscopic Characteristics
- The eczematous reaction does not significantly distort the dermoscopic pattern of the underlying nevus. This is a critical teaching point.
- Structures and patterns may appear less focused due to overlying fine superficial scale or serocrusts.
- The underlying nevus pattern (reticular, globular, homogeneous) remains recognizable through the inflammatory overlay.
Clinical Pearl: If the structures of the underlying nevus are difficult to evaluate through the eczematous reaction, treat the eczema with topical corticosteroids first. Re-evaluate the lesion dermoscopically once the inflammation has resolved to obtain a clear view of the nevus architecture.
4.1.3 Cockade Nevi
Clinical Overview
Cockade nevi display a distinctive targetoid pattern. Key features include:
- Clinical morphology: Central pink to brown papule or macule, surrounded by an inner hypopigmented rim and an outer pigmented rim.
- Demographics: Often found on the scalp of children and adolescents.
- Histologic correlation: The central portion corresponds to a compound nevus, while the peripheral portion shows a nonpigmented junctional nevus pattern. This histologic zonation produces the targetoid clinical appearance.
Dermoscopic Characteristics
- Targetoid appearance: A darker, central area with a globular or homogeneous pattern.
- Inner rim: A hypopigmented homogeneous structureless zone surrounds the central darker area.
- Outer rim: A peripheral darker reticular outer rim.
Clinical Pearl: Cockade nevi on the scalp of children are benign and do not require biopsy. Recognition of the targetoid pattern -- a darker center, a lighter middle ring, and a darker outer ring with network -- is sufficient for confident clinical diagnosis.
4.2 Melanoma Simulators
4.2.1 Recurrent Nevi (Post-Biopsy/Excision)
Clinical Overview
Recurrent nevi are defined as proliferations of nevomelanocytes occurring after the partial surgical or traumatic removal of a melanocytic nevus. Key features include:
- Demographics: Most commonly occur on the back of young adults.
- Timeline: Often develop within the first 3 to 8 months after incomplete removal.
- Clinical significance: Although recurrent nevi may clinically simulate melanoma (hence the term "pseudomelanoma"), dermoscopy has proven useful in differentiating them from true melanoma recurrence.
Dermoscopic Characteristics
The dermoscopic hallmarks of recurrent nevi are:
- Pigmentation confined to the scar: The pigment does not traverse from the scar into the surrounding normal skin. This is the single most important differentiating feature.
- Centrifugal growth pattern: Radial lines that are symmetric, radiating outward from the center of the scar.
- Contiguous and centrifugal arrangement: Pigmented structures are arranged contiguously (without skip areas) and follow a centrifugal pattern.
Differences Between Recurrent Nevi and Recurrent Melanoma
| Parameter | Recurrent Nevi | Recurrent Melanoma |
|---|---|---|
| Age | Younger patients | Older patients |
| Location | Torso | Head and neck |
| Average time to recurrence | 8 months | 25 months |
| Pigment distribution | Confined to scar; contiguous | Traverses the scar's edge; noncontiguous |
| Growth pattern | Centrifugal (symmetric radial) | Chaotic (disorganized) |
(Source: Blum A, et al., JAMA Dermatol, 150(2), 138--145, 2014.)
Critical Decision Points
The following findings should prompt concern for recurrent melanoma rather than recurrent nevus:
- Pigment extending beyond the scar margin into surrounding normal skin
- Noncontiguous pigmented structures (skip areas)
- Chaotic (rather than centrifugal) growth pattern
- Older patient age
- Head and neck location
- Recurrence after more than 12 months
Clinical Pearl: Always correlate dermoscopic findings with the clinical history. Knowing the original histopathologic diagnosis is essential. If the original lesion was a benign nevus and the recurrent pigmentation is confined to the scar with a centrifugal pattern, observation with dermoscopic monitoring is appropriate. If the original diagnosis was melanoma, or if the recurrent pigmentation shows chaotic or scar-transgressing features, re-excision and histopathologic evaluation are mandatory.
Clinical Scenario
A 30-year-old woman had a compound nevus partially excised from her upper back 5 months ago (pathology confirmed benign). She now notices brown pigmentation within the scar. Dermoscopy shows pigmented streaks confined to the scar boundaries, arranged in a symmetric centrifugal pattern radiating outward from the center, with no pigment crossing the scar edge.
What is the diagnosis, and what features would change your management?
Recurrent Nevus (Pseudomelanoma)
Pigmentation confined to the scar with a contiguous centrifugal growth pattern is the hallmark of a recurrent nevus. The young age, trunk location, and recurrence within 8 months are all consistent with benign recurrence. Features that would prompt re-excision: pigment extending beyond the scar margin, noncontiguous (skip) pigmented structures, chaotic growth pattern, or recurrence after >12 months. If the original pathology had shown melanoma, any recurrent pigmentation would require re-excision.
4.2.2 Lichen Sclerosus Nevi
Clinical Overview
Lichen sclerosus (LS) is a chronic inflammatory skin disease of unknown etiology with the following features:
- Predilection: Anogenital area of female patients.
- Clinical appearance: White, ivory-colored macules or patches, which may reveal focal ecchymotic areas.
- Nevus development in LS: Rarely, a melanocytic nevus can develop within LS. It is hypothesized that the altered stroma may lead to melanocyte activation, resulting in their proliferation.
- Demographics: Most commonly occurs in children and young adults.
- Clinical concern: The morphology created when nevi and LS collide mimics melanoma, making dermoscopic evaluation challenging.
Dermoscopic Characteristics
Features of the nevus component:
- Nevi developing in LS usually reveal a parallel, globular, or homogeneous pattern.
- A multicomponent pattern is not uncommon -- this is what creates the melanoma-simulating appearance.
Features of the LS component:
- Porcelain white structureless areas -- the hallmark dermoscopic finding of LS.
- Comedo-like openings may be present.
- Lesions may or may not display vessels or shiny white lines.
Management Strategy
- In the presence of a pigmented lesion in the genitalia, always evaluate the surrounding skin and the entire anogenital area to rule out the presence of LS.
- Some atypical findings observed in nevi arising on LS are due to inflammation and altered stroma, not malignant transformation.
- Treating the LS with topical steroids may improve some of the atypical features observed in these nevi. This can be used as a diagnostic maneuver: treat the LS, then re-evaluate the pigmented lesion dermoscopically.
- If atypical features persist after LS treatment, biopsy should be considered.
Clinical Pearl: Do not reflexively biopsy every pigmented lesion in the anogenital area with LS. First assess the surrounding skin for evidence of LS. If LS is confirmed, consider treating the LS with topical corticosteroids and re-evaluating the pigmented lesion dermoscopically in 2--3 months. The atypical dermoscopic features may improve as the inflammation subsides.
Check Your Understanding
What is a halo nevus, and what does it look like on dermoscopy?
A halo nevus (Sutton nevus) shows a central melanocytic nevus surrounded by a white depigmented ring. Dermoscopically, the central nevus may show a globular or homogeneous pattern, while the halo zone is white and structureless. A scar-like or regression-like pattern may develop in the central nevus as the immune response progresses.
Key Takeaways
- Halo nevi show a symmetric melanocytic pattern (reticular, globular, or homogeneous) surrounded by a white depigmented halo corresponding to lymphocytic destruction of melanocytes.
- Meyerson nevus features an eczematous inflammatory halo with yellow scale and spongiotic changes around an otherwise typical nevus; dermoscopy shows the nevus pattern plus inflammatory features.
- The dermoscopic pattern of the central nevus in halo and Meyerson nevi should be evaluated independently of the surrounding reaction to exclude melanoma.
4.3 Other Uncommon Variants
4.3.1 Balloon Cell Nevi (BCN)
Clinical Overview
Balloon cell nevi are a rare variant of melanocytic nevi with distinctive features:
- Demographics: Often found on the head and trunk of children and young adults.
- Clinical appearance: Relatively symmetric, pink or light brown macule or papule with a flat, raised, or mammillated surface.
- Histopathology: Characterized by dermal lobules of large multinucleated cells with small round central nuclei. Balloon cells are melanocytes with extensive pale-staining and vacuolated cytoplasm, often resulting from a defect in melanosome formation.
Dermoscopic Characteristics
- The hallmark feature is three or more aggregated white-to-yellow globules.
- These globules correspond histologically to balloon cell nests in the dermis.
Important Distinction from Milia-Like Cysts
| Feature | BCN White Globules | Milia-Like Cysts |
|---|---|---|
| Polarization behavior | Equally visible with both polarized and nonpolarized light | More conspicuous with nonpolarized light |
| Color | White-to-yellow | Bright white |
| Histologic correlate | Balloon cell nests (melanocytes with vacuolated cytoplasm) | Intraepidermal keratin cysts |
| Clinical context | Rare nevus variant in young patients | Seborrheic keratosis, solar lentigo |
Clinical Pearl: The polarization behavior of white globules is a key diagnostic clue. In BCN, white globules are seen equally well with both polarized and nonpolarized dermoscopy. Milia-like cysts, by contrast, are more conspicuous with nonpolarized light. Use a hybrid dermatoscope to toggle between modes and assess this difference.
4.3.2 Epidermolysis Bullosa Nevi (EB Nevi)
Clinical Overview
Epidermolysis bullosa (EB) is a group of mechanobullous diseases arising from various mutations in keratin proteins at the dermo-epidermal junction. Key features of EB nevi:
- Prevalence: Up to 14% of patients with all forms of inherited EB develop new nevi.
- EB forms: Large atypical nevi are more commonly seen in patients with the recessive inherited forms of EB. EB is classified into epidermolytic (simplex), junctional, and dermolytic (dystrophic) based on the level of cleavage.
- Demographics: Usually arise during the first two decades of life.
- Location: Frequently found on sites of prior blisters, particularly on extremities overlying bony prominences.
- Clinical appearance: Relatively large, asymmetric, and irregularly pigmented neoplasms. Small satellite nevi may develop around the primary EB nevus.
Pathogenesis
Two theories have been proposed:
- Reactive proliferation theory: Repetitive disruption of the basement membrane triggers increased melanocyte proliferation.
- Free-floating melanocyte theory: Free-floating melanocytes within the cytokine milieu of an EB blister settle onto the epidermis and begin to proliferate.
Dermoscopic Characteristics
EB nevi can demonstrate features that overlap significantly with melanoma, including:
- Multicomponent pattern
- Atypical pigment network
- Irregular dots and globules
- Milky-red areas
This degree of overlap with melanoma features makes EB nevi one of the most challenging diagnostic scenarios in dermoscopy.
Melanoma Risk in EB
- Melanoma is not common in any form of EB.
- Only patients with the recessive dystrophic form have a slightly increased lifetime risk (cumulative risk of 2.5% by age 12).
- A 20-year prospective study of 86 EB nevi (Bauer et al., 2001) showed that none of the pigmented lesions progressed to melanoma.
- Two cases of melanoma arising on EB-affected skin have been reported in the literature, both in female adults (ages 26 and 30) with EB simplex.
Recommended Monitoring Strategy
Due to the significant dermoscopic overlap with melanoma and the (low) risk of malignant transformation:
- Clinical images: Perform baseline clinical photography.
- Digital dermoscopy: Capture baseline dermoscopic images for sequential comparison.
- Total body photography: Recommended for comprehensive monitoring.
- Biopsy threshold: Consider skin biopsy in cases of:
- New lesions, especially on EB-affected skin
- Changing lesions (evolution in dermoscopic features)
- Older age of onset
Clinical Pearl: EB nevi are a diagnostic trap because their dermoscopic features can overlap almost completely with melanoma. Do not biopsy every EB nevus reflexively -- this would lead to unacceptable morbidity in patients already dealing with a severe skin fragility disorder. Instead, establish a robust digital monitoring program and biopsy only when new lesions appear, established lesions change, or the clinical context is concerning (older patient, new onset on previously clear skin).
4.4 When to Worry About "Special" Nevi
The following clinical and dermoscopic features should raise concern for malignancy in the context of special nevus variants:
| Finding | Concern Level | Recommended Action |
|---|---|---|
| Halo nevus with multicomponent central pattern | High | Excisional biopsy |
| Asymmetric, irregular halo distribution | Moderate-High | Excisional biopsy |
| Recurrent pigment traversing scar margin | High | Re-excision with histopathology |
| Chaotic growth pattern in recurrent lesion | High | Re-excision with histopathology |
| Recurrence >12 months after excision | Moderate | Close monitoring or re-excision |
| LS nevus with persistent atypical features after topical steroid treatment | Moderate-High | Biopsy |
| EB nevus with new or changing features | Moderate-High | Biopsy |
| EB nevus with older age of onset | Moderate | Biopsy |
| Meyerson nevus with atypical structures after eczema resolution | Moderate | Biopsy |
Check Your Understanding
How do recurrent (persistent) nevi present on dermoscopy after partial removal?
Recurrent nevi show pigmentation within or at the border of a surgical scar. Dermoscopically, they display streaks or lines oriented parallel to the scar, creating a pattern that can mimic melanoma. The key to correct diagnosis is the clinical history of prior surgery at the same site and the linear arrangement of pigment along the scar axis.
Key Takeaways
- Recurrent (persistent) nevus after incomplete excision shows streaks and structureless pigmentation confined to the scar area; extension beyond the scar border raises concern for melanoma.
- Nevus spilus shows a background cafe-au-lait macule with superimposed darker macules or papules that individually display benign nevus patterns (reticular, globular).
- Cockade (targetoid) nevi feature concentric rings of alternating pigmented and depigmented zones and are a benign variant requiring no treatment.
4.5 Differential Diagnosis Considerations
4.5.1 White Halo Around a Lesion
| Diagnosis | Key Distinguishing Features |
|---|---|
| Halo nevus | Benign central nevus (globular/homogeneous), symmetric uniform white halo, children/young adults |
| Melanoma with regression | Multicomponent central pattern, irregular/asymmetric halo, melanoma-specific structures, older adults |
| Vitiligo with incidental nevus | Depigmentation not centered on nevus, may affect multiple body sites, Wood lamp enhancement |
4.5.2 Recurrent Pigmentation in a Scar
| Diagnosis | Key Distinguishing Features |
|---|---|
| Recurrent nevus | Pigment confined to scar, centrifugal symmetric growth, contiguous pigment, younger patients, torso, ~8 months post-excision |
| Recurrent melanoma | Pigment traverses scar edge, chaotic growth, noncontiguous pigment, older patients, head/neck, ~25 months post-excision |
4.5.3 Targetoid/Ring-Like Pattern
| Diagnosis | Key Distinguishing Features |
|---|---|
| Cockade nevus | Central compound nevus, inner hypopigmented rim, outer pigmented reticular rim; scalp of children |
| Halo nevus | Central nevus with complete white depigmentation halo; trunk of children/young adults |
| Eclipse nevus | Peripheral rim of brown globules with central tan homogeneous area (see Module 16) |
4.5.4 Pigmented Lesion in Anogenital Area
| Diagnosis | Key Distinguishing Features |
|---|---|
| LS nevus | Pigmented lesion within porcelain white LS patch, parallel/globular/homogeneous (or multicomponent) pattern, may improve with topical steroids |
| Genital melanotic macule | Structureless brown pigmentation, parallel pattern on mucosal surface |
| Melanoma | Multicomponent pattern, blue-whitish veil, irregular vessels, asymmetry; does not improve with steroid treatment |
Key Takeaways
- Any halo nevus with asymmetric internal structure, atypical network, or blue-white veil warrants excision to exclude regressing melanoma.
- Multiple halo nevi may be associated with vitiligo or, rarely, with melanoma at a distant site (paraneoplastic phenomenon), particularly in adults.
- Recurrent pigmentation after biopsy should be evaluated with dermoscopy and clinical history; if the original histology was benign and pigmentation stays within the scar, observation is acceptable.
5. Special Nevus Variants Reference Table
| Variant | Synonym(s) | Typical Demographics | Typical Location | Dermoscopic Pattern | Key Dermoscopic Features | Melanoma Risk |
|---|---|---|---|---|---|---|
| Halo nevus | Sutton nevus, leukoderma acquisitum centrifugum | Children, young adults | Trunk | Globular or homogeneous center + white halo | Symmetric white structureless area surrounding central dots/globules or homogeneous tan; gray dots/granules during regression; pink center after complete involution | Very low (but evaluate central lesion) |
| Meyerson nevus | Eczematous nevus | Young adults | Trunk, upper extremities | Underlying nevus pattern preserved | Overlying scale/serocrusts may blur structures; pattern appears less focused but not distorted; eczema resolves in weeks to months | Very low |
| Cockade nevus | Targetoid nevus | Children, adolescents | Scalp | Targetoid trilaminar pattern | Central darker globular/homogeneous area, inner hypopigmented structureless rim, outer darker reticular rim | Very low |
| Recurrent nevus | Pseudomelanoma | Young adults | Back (torso) | Centrifugal pigmentation within scar | Pigment confined to scar, symmetric radial lines, contiguous and centrifugal arrangement; pigment does not traverse scar edge | Low (but must distinguish from recurrent melanoma) |
| LS nevus | Lichen sclerosus nevus | Children, young adults | Anogenital area | Parallel, globular, homogeneous, or multicomponent | Porcelain white structureless areas (LS component), comedo-like openings, variable vessels/shiny white lines; nevus may show multicomponent pattern | Low (melanoma-simulating features due to altered stroma) |
| Balloon cell nevus | BCN | Children, young adults | Head, trunk | Aggregated white-to-yellow globules | Three or more aggregated white-to-yellow globules (balloon cell nests), equally visible with polarized and nonpolarized light | Very low |
| EB nevus | Epidermolysis bullosa nevus | First two decades of life | Extremities (bony prominences), sites of prior blisters | Multicomponent (melanoma-like) | Atypical pigment network, irregular dots/globules, milky-red areas; satellite nevi possible | Low overall; slightly elevated in recessive dystrophic EB (2.5% cumulative by age 12) |
6. Clinical Pearls
The halo tells you about the immune system, not the nevus: A symmetric white halo is a sign of T-cell-mediated regression, not malignancy. Focus your dermoscopic evaluation on the central nevus -- only the architecture of the central lesion determines whether biopsy is needed.
Halo nevi and vitiligo share an immunologic link: Patients with halo nevi may have or develop vitiligo, and vice versa. Inquire about personal and family history of autoimmune disorders when evaluating halo nevi.
Halo nevi take 8 years to resolve: Counsel patients and families about the prolonged timeline. After complete involution of the central nevus, a pink area persists before eventual re-pigmentation.
Meyerson eczema is treatable and temporary: Do not biopsy a Meyerson nevus solely because the eczematous reaction obscures the dermoscopic pattern. Treat with topical corticosteroids and re-evaluate dermoscopically once the inflammation resolves.
Cockade nevi on the scalp of children require no biopsy: The characteristic three-zone targetoid pattern (central dark area, inner light ring, outer dark ring with network) is diagnostic and does not require histologic confirmation.
For recurrent nevi, the scar is the boundary: The most reliable dermoscopic criterion distinguishing a recurrent nevus from recurrent melanoma is whether pigmentation is confined to the scar. Pigment that transgresses the scar margin is a red flag.
Time to recurrence is diagnostically useful: Recurrent nevi typically appear within 8 months of excision, while recurrent melanomas average 25 months. A recurrence appearing more than a year post-excision warrants heightened suspicion.
Always examine the surrounding skin for LS: When encountering a pigmented lesion in the anogenital area, systematically evaluate the surrounding skin for porcelain white patches. If LS is present, it may explain atypical dermoscopic features in the nevus.
Treat LS before deciding on biopsy: Topical steroid treatment of the LS may normalize some atypical dermoscopic features of nevi arising within LS. Use this as a diagnostic maneuver before proceeding to biopsy.
BCN globules differ from milia-like cysts by polarization behavior: Use a hybrid dermatoscope to toggle between modes. BCN white globules are equally visible with polarized and nonpolarized light, while milia-like cysts are more conspicuous with nonpolarized light alone.
EB nevi require a monitoring program, not serial biopsies: Given the skin fragility in EB patients, establish digital dermoscopy monitoring with clinical photography and total body photography. Reserve biopsy for new, changing, or late-onset lesions.
Two reported melanomas in EB patients -- both in adult women with EB simplex: The rarity of melanoma in EB underscores that EB nevi are almost always benign, but vigilance is still warranted, particularly in adults with changing lesions.
Clinical Vignettes
Clinical Scenario A 15-year-old boy presents with a 6 mm brown lesion on the right upper back surrounded by a well-defined, symmetric ring of depigmentation (white halo). Dermoscopy of the central component reveals a homogeneous tan pattern with scattered regular globules. The surrounding white zone is structureless and symmetric. No irregular streaks, blue-white veil, regression structures, or atypical vessels are present.
What is the most likely diagnosis?
Diagnosis: Halo nevus (Sutton nevus).
The symmetric white halo surrounding a melanocytic lesion with benign dermoscopic features is characteristic of a halo nevus. Clinical Pearl 1 applies: the halo tells you about the immune system (T-cell-mediated regression), not about the nevus itself. The diagnostic focus should be on the central nevus -- here it shows a homogeneous/globular pattern, which is one of the typical patterns seen in halo nevi. If the central component showed a reticular pattern (seen in only 7% of halo nevi), melanoma exclusion would be warranted (Clinical Pearl 10 from Module 16). The patient and family should be counseled that halo nevi take approximately 8 years to fully resolve (Clinical Pearl 3). Inquire about autoimmune conditions, as halo nevi and vitiligo share an immunologic link (Clinical Pearl 2).
Clinical Scenario A 40-year-old woman had a shave biopsy 6 months ago on the left upper arm for a compound nevus (histopathology confirmed benign). She now notes brown pigmentation reappearing at the scar site. Dermoscopy shows symmetric, centrifugally arranged streaks of brown-to-gray pigment that are entirely confined within the scar boundaries. The pigment does not cross the scar margin. No irregular dots, blue-white veil, or atypical vessels are visible beyond the scar.
What is the most likely diagnosis?
Diagnosis: Recurrent nevus (pseudomelanoma).
This case demonstrates the most reliable dermoscopic criterion for distinguishing recurrent nevus from recurrent melanoma (Clinical Pearl 6): pigmentation is confined to the scar with symmetric centrifugal growth. The 6-month recurrence interval falls within the typical timeframe for recurrent nevi (Clinical Pearl 7: recurrent nevi average <8 months, while recurrent melanomas average 25 months). If pigment were to transgress the scar margin into normal surrounding skin with a chaotic pattern, recurrent melanoma would need to be excluded urgently. The original benign histopathology is reassuring, but ongoing monitoring is still advisable.
Clinical Scenario A 22-year-old man with epidermolysis bullosa simplex presents for a skin check. Multiple brown-black lesions are present on the trunk and extremities, many at sites of previous blistering. One 8 mm lesion on the right forearm shows a multicomponent pattern on dermoscopy with irregular dots, structureless areas of different colors, and focal areas of dark brown pigmentation. It appeared 3 months ago at a site of recent trauma.
What is the most likely diagnosis?
Diagnosis: Epidermolysis bullosa (EB) nevus -- but the new onset and multicomponent pattern require careful assessment.
EB nevi frequently display atypical dermoscopic features (multicomponent patterns, irregular dots, multiple colors) that would normally prompt biopsy in the general population. The development at a site of previous blistering/trauma is characteristic of EB nevi, which arise within the inflammatory microenvironment of EB skin. While EB nevi are almost always benign, melanoma has been reported in EB patients -- both in adult women with EB simplex (Clinical Pearl 12). Given the skin fragility in EB, serial biopsies should be avoided. Instead, establishing a digital dermoscopy monitoring program with clinical photography and total body photography is recommended (Clinical Pearl 11). Biopsy should be reserved for new, changing, or late-onset lesions, with the clinical context guiding the threshold for intervention.
8. Cross-References
| Topic | Chapter | Pages |
|---|---|---|
| Introduction to other nevi (targetoid nevi, melanoma simulators, uncommon variants) | Chapter 7f | p. 176 |
| Halo nevi (Sutton nevi) -- clinical features and dermoscopy | Chapter 7f | p. 176 |
| Meyerson nevi -- clinical and dermoscopic features | Chapter 7f | p. 176 |
| Cockade nevi -- clinical features and dermoscopy | Chapter 7f | pp. 176--177 |
| Recurrent nevi -- dermoscopic features and differentiation from recurrent melanoma | Chapter 7f | p. 177 |
| Differences between recurrent nevi and recurrent melanoma | Chapter 7f | p. 177 |
| Lichen sclerosus nevi -- dermoscopy and management | Chapter 7f | p. 177 |
| Balloon cell nevi -- dermoscopic features | Chapter 7f | p. 177 |
| Epidermolysis bullosa nevi -- dermoscopy and monitoring | Chapter 7f | pp. 177--178 |
| EB nevi melanoma risk and prospective data | Chapter 7f | p. 178 |
| Melanoma-specific structures (for differential diagnosis) | Chapters 8a--8f | pp. 191--226 |
| Globular and homogeneous patterns in acquired nevi | Chapter 7b | pp. 157--167 |
| Regression structures (gray dots, granularity) | Chapter 3 | pp. 20--52 |
Key Illustrations:
- Dermoscopy images of a halo nevus -- demonstrating the symmetric white structureless halo surrounding a central nevus.
- Meyerson nevus on the nasolabial skin of a young female -- showing the eczematous reaction (erythema and scale) surrounding the nevus with dermoscopic structures appearing less focused due to overlying serocrust.
- Dermoscopy image of a cockade nevus -- demonstrating the targetoid pattern with central brown flat papule, inner hypopigmented rim, and outer pigmented network rim.
- Recurrent nevus on the abdomen of a young male -- showing brown pigmentation confined to the scar with centrifugal growth pattern and symmetric radial lines that do not traverse the scar.
- Young girl with history of lichen sclerosus who developed an irregular dark brown lesion within sclerotic skin -- biopsy revealed features commonly associated with recurrent nevi.
- Dermoscopy image of a balloon cell nevus -- showing aggregated white globules (three or more) visible with both polarized and nonpolarized light, corresponding to balloon cell nests.
9. Related Modules
Module 15: Congenital Melanocytic Nevi (
module_15_congenital_nevi.md) -- Congenital nevi provide context for understanding large atypical nevi in the EB setting and the baseline patterns (globular, cobblestone) that may be altered by blister-related melanocyte proliferation.Module 16: Acquired Melanocytic Nevi (
module_16_acquired_nevi.md) -- The globular, reticular, and homogeneous patterns of common acquired nevi form the substrate upon which targetoid modifications (halo, cockade, Meyerson) are recognized. Eclipse nevi share the concentric morphology discussed here.Module 17: Intradermal Nevus (
module_17_intradermal_nevus.md) -- Intradermal nevi frequently serve as the central nevus in halo nevi and may display the homogeneous pattern that characterizes these targetoid variants.Module 18: Blue Nevi and Variants (
module_18_blue_nevi.md) -- Combined nevi and blue nevus patterns provide important differential diagnosis context, particularly for lesions with blue-gray or multicomponent features.Module 19: Spitz and Reed Nevi (
module_19_spitz_reed_nevi.md) -- Spitzoid features may overlap with atypical findings in EB nevi and other special variants. The starburst pattern of Spitz nevi should be distinguished from the radial lines in recurrent nevi.Module 21: Superficial Spreading Melanoma (
module_21_ssm.md) -- Understanding melanoma-specific structures (atypical network, irregular dots/globules, blue-whitish veil, regression) is essential for the differential diagnosis of recurrent nevi, LS nevi, and EB nevi -- all of which can simulate melanoma.Module 28: Improving Sensitivity and Specificity (
module_28_sensitivity_specificity.md) -- Sequential monitoring strategies discussed in that module are directly applicable to the management of EB nevi and other special variants requiring long-term follow-up.Module 32: Mucosal Surfaces (
module_32_mucosal.md) -- Mucosal and genital dermoscopy patterns are relevant to the evaluation of lichen sclerosus nevi in the anogenital area.Module 37: Digital Monitoring (
module_37_digital_monitoring.md) -- Digital dermoscopy, total body photography, and sequential monitoring are the cornerstones of EB nevi management and are applicable to follow-up of all special nevus variants.
This module is part of the Dermoscopy Educational Course. For the complete course outline and suggested study paths, see COURSE_OUTLINE.md.