Module 31: Special Locations -- Palms and Soles (Volar Surface)

Volar skin (palms and soles) possesses a unique microanatomy that produces the individualized dermatoglyphic patterns (fingerprints and footprints) we all carry. This same microanatomy is directly responsible for the characteristic parallel pigment line patterns observed under dermoscopy in melanocytic lesions on these surfaces. Understanding the underlying anatomy is the key to correctly interpreting volar lesion dermoscopy.

The surface of volar skin consists of alternating:

• Sulci (furrows / sulcus superficialis): The narrow grooves of the dermatoglyphics, approximately 0.2 mm in width.
• Cristae (ridges / crista superficialis): The broader elevated lines, approximately 0.5 mm in width. The eccrine sweat ducts open on the surface of the ridges.

Beneath the surface, two types of rete ridges create these structures:

• Crista limitans: The rete ridge associated with the furrow. Benign melanocytes preferentially localize here.
• Crista intermedia: The rete ridge associated with the ridge. The eccrine duct traverses through this structure. Melanoma cells tend to cluster here during early growth phases.

The single most important concept in volar dermoscopy is this: In nevi, pigment is preferentially deposited in the furrows; in melanoma, pigment is preferentially deposited on the ridges. This principle underlies all acral dermoscopic pattern analysis and algorithm construction.

The Wallace line is the demarcation boundary separating glabrous (non-hair-bearing) volar skin from nonglabrous (hair-bearing) skin on the hands and feet. Lesions below the Wallace line display parallel line patterns characteristic of volar skin. Lesions above the Wallace line display conventional dermoscopic criteria of nonglabrous skin (e.g., reticular pattern). Melanocytic lesions that straddle the Wallace line frequently display a multicomponent transition pattern combining features of both skin types, which can appear atypical.

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A detailed understanding of the histologic microanatomy of volar skin underpins dermoscopic interpretation:

4.1.1 The Tyndall Effect in Volar Skin

In nonglabrous skin, eumelanin pigment located in the upper dermis appears brown, and eumelanin in the lower dermis appears bluish. This is due to the Tyndall effect: melanin appears black when superficial, brown when slightly deeper, and blue when deep within the skin. On volar skin, the stratum corneum is significantly thickened compared with nonglabrous skin. This thickened corneal layer shifts the apparent depth at which pigment sits, which explains why most compound nevi appear brown on nonvolar skin but have a characteristic bluish hue when located on the palms and soles.

4.1.2 Furrows, Ridges, and Their Underlying Rete Ridges

• Furrows (sulcus superficialis) and ridges (crista superficialis) are created by two types of rete ridges:
• The crista limitans corresponds to the furrow.
• The crista intermedia corresponds to the ridge.
• The eccrine duct traverses through the crista intermedia and opens on the surface of the ridge.
• In nevi, melanocytes preferentially localize around the crista limitans and transfer melanin pigment to keratinocytes associated with the furrow. This produces the parallel furrow pattern.
• In early melanoma, melanoma cells tend to cluster around the crista intermedia (where melanocytic stem cells reside near the sweat glands). This produces the parallel ridge pattern.

4.1.3 Differentiating Ridges from Furrows

While differentiating furrows from ridges is usually straightforward, it can occasionally be challenging. Three reliable clues help:

1. Width: Ridges are wider (~0.5 mm) than furrows (~0.2 mm).
2. Eccrine duct openings: Visible as small white dots evenly distributed along the center of the ridge on dermoscopy.
3. The ink test: Apply a felt-tip marker to the skin surface, then wipe off excess ink with an alcohol swab. The ink highlights the ridges and eccrine duct openings, making it straightforward to determine whether the lesion's pigment is on the ridges or in the furrows.

4.1.4 Additional Anatomic Features

• Absence of follicular openings: Volar skin is glabrous (non-hair-bearing), so follicular openings are absent.
• The Wallace line: Lesions below this line show parallel patterns; those above show conventional dermoscopic criteria. Lesions at the junction display a transition pattern with features of both glabrous and nonglabrous skin.

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flowchart TD
 A[Volar Melanocytic<br/>Lesion] --> B{Pigment on Furrows<br/>or Ridges?}
 B -->|Furrows| C{Pattern Type?}
 B -->|Ridges| D[Parallel Ridge Pattern<br/>-- Suspect Melanoma]
 B -->|Both / Diffuse| E{Lesion > 7 mm?}
 C -->|Parallel furrow| F[Benign -- Most<br/>Common Nevus Pattern]
 C -->|Lattice-like| G[Benign -- Typically<br/>Arch of Foot]
 C -->|Fibrillar| H{Type A or B?}
 C -->|Globular| I[Benign -- Likely<br/>Congenital Nevus]
 C -->|Homogeneous| J[Benign -- Monitor<br/>if > 7 mm]
 C -->|Nontypical| K[Evaluate with<br/>BRAAFF Algorithm]
 H -->|Type A: Uniform| L[Benign -- Weight-<br/>Bearing Sole]
 H -->|Type B: Variable<br/>color/thickness| M[Suspicious --<br/>Consider Biopsy]
 D --> N[Apply BRAAFF<br/>Score >= 1: Biopsy]
 E -->|Yes| N
 E -->|No| K

There is a pervasive myth in medicine that all melanocytic lesions on palms and soles should be excised. This myth may persist because volar nevi are relatively uncommon and because the clinical morphologic features of nevi and early melanoma overlap significantly, making naked-eye differentiation difficult. However, with dermoscopy, it has become relatively straightforward to identify nevi and melanoma based on the preferential localization of pigment in the furrows (nevi) versus the ridges (melanoma).

Occasionally, pigment may be distributed diffusely across both the ridges and furrows without preferential localization, resulting in homogeneous pigmented areas. Such a pattern should raise concern for melanoma, particularly in lesions greater than 7 mm.

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Check Your Understanding

What is the most important dermoscopic feature distinguishing benign acral nevi from acral melanoma?

The most important distinguishing feature is the parallel pattern: benign acral nevi show the parallel furrow pattern (pigment follows the sulci/furrows), while acral melanoma shows the parallel ridge pattern (pigment follows the ridges/cristae). This distinction has high sensitivity and specificity for melanoma on acral skin.

Key Takeaways

• The parallel furrow pattern (pigment along dermatoglyphic furrows) is the most common benign acral dermoscopic pattern, corresponding to melanocytes in the crista limitans rete ridges.
• Multiple benign variants exist: classic parallel furrow, lattice-like (furrow lines connected across ridges), and fibrillar (oblique lines from shearing forces).
• The crista dotted pattern (dots on ridges) is a benign variant predominantly seen in children and on the lateral aspects of fingers and toes.

An important principle to bear in mind before classifying patterns is context: history, skin type, age, and location all factor into the final management decision. Miyazaki et al. demonstrated that the distribution of the three most common benign dermoscopic patterns is not random:

• Lattice-like pattern: Located mainly on the arch of the foot.
• Fibrillar pattern: Located on the weight-bearing parts of the foot.
• Parallel furrow pattern: Located between the arch and weight-bearing portion.

Until further evidence establishes whether patterns located in "atypical" anatomic positions retain the same benign significance, lesions displaying a benign-appearing pattern in the "wrong" location should be managed with caution.

4.3.1 Parallel Furrow Pattern

Description: Linear pigmentation predominantly localized to the furrows. This is the most common benign pattern on volar skin.

Histologic correlate: Melanocytes preferentially located around the crista limitans with melanin columns arranged vertically in the epidermis and stratum corneum.

Four subtypes (variants):

Subtype	Description
Single line	A single continuous line of pigment within the furrow
Double line	Two parallel lines of pigment flanking the furrow
Single dotted line	A single row of dots within the furrow
Double dotted line	Two parallel rows of dots along both sides of the furrow

Typical locations: Commonly seen on palms or on the sole between the arch and the weight-bearing portion.

Diagnostic clue: The nonpigmented ridges are wider than the pigmented furrows, and white dots (eccrine duct openings) are visible on the ridges.

4.3.2 Lattice-Like Pattern

Description: Similar to the parallel furrow pattern but with the addition of parallel pigment bands that cross over the ridges from one furrow to the next, resembling the rungs of a ladder.

Typical location: The arch area of the sole. This is the most common pattern of nevi found on the arch. It can also be seen on the palms.

4.3.3 Fibrillar Pattern

Description: Multiple thin parallel lines oriented obliquely (tangentially) to the dermatoglyphics, appearing to cross both the furrows and the ridges.

Mechanism: Persistent horizontal pressure applied to the stratum corneum causes it to grow in a slanted direction (in the direction of lateral pressure). As linearly oriented melanin-laden epidermal cells in the stratum granulosum move into the stratum corneum, they travel in an oblique direction, converting a parallel furrow or ridge pattern into a fibrillar pattern.

Typical location: Weight-bearing parts of the sole. The fibrillar pattern is not normally seen on the palms because persistent weight-bearing forces do not occur there.

Critical distinction -- Type A (benign) versus Type B (suspicious):

Feature	Type A (Benign)	Type B (Suspicious)
Line thickness	Thin, uniform	Variable, often thicker
Color	Light brown, minimal variation	Variable; gray hues (uncommon in nevi)
Distribution	Organized, regular	Disorganized
Location	Weight-bearing plantar skin	Any location

Important clinical rule: ANY fibrillar pattern on the palms (regardless of appearance) should raise suspicion for ALM, because constant frictional pressure on the palms does not normally occur.

Oblique-view dermoscopy: A diagnostic technique that can help unmask the underlying pattern (furrow or ridge) hidden by the fibrillar artifact. Viewing the lesion at an oblique angle, or applying downward and horizontal pressure opposite to the normal frictional forces, can transiently convert the fibrillar pattern back into a parallel pattern, revealing whether the pigment originates from the furrows or the ridges.

4.3.4 Globular Pattern

Description: Globules (corresponding to nests of nevomelanocytes of varying sizes) not associated with a parallel pattern. These lesions are presumed to represent congenital nevi.

4.3.5 Reticular Pattern

Description: A well-defined pigment network not associated with the skin markings. This is a nontypical pattern for volar skin but can be seen on the arch of the foot, where nevi usually display a lattice-like pattern.

4.3.6 Homogeneous Pattern

Description: Uniformly distributed pigment involving both the furrows and ridges, devoid of any other dermoscopic structures. Some nevi with a parallel furrow pattern transform over time into a homogeneous pattern. Digital dermoscopy follow-up has shown that some homogeneous-patterned nevi eventually fade away via transepidermal elimination of melanocytes.

Caution: Homogeneous diffuse pigmentation with variable shades of brown in lesions larger than 7-10 mm should raise concern for melanoma.

4.3.7 Peas-in-a-Pod Pattern

Description: A variant of the parallel furrow pattern consisting of parallel furrow lines (in any of the four subtypes) in combination with dots/globules located adjacent to or in the center of the ridges. Sometimes the globules on the ridges are visible but the furrow pigment is not.

Association: Congenital nevi on volar skin.

Additional congenital nevus feature: The "crista dotted pattern" (dots on the ridges) is also commonly seen in congenital nevi.

4.3.8 Nontypical (Nondescript) Pattern

Description: A pattern that cannot be classified into any of the recognized benign patterns and also does not display melanoma-specific patterns. This is an intermediate category.

Management: These lesions require careful evaluation. Context (age, size, location, history) becomes particularly important. The decision to biopsy or monitor depends on additional features such as:

• Maximum diameter (>7 mm is suspicious)
• Asymmetry of color or structure
• Presence of more than two colors
• Blue-white structures, vessels, dots, streaks, or abrupt edges
• Patient age and clinical history

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Clinical Scenario

A 58-year-old woman presents with a slowly expanding pigmented macule on her left sole present for 2 years. Dermoscopy reveals diffuse pigmentation following the sulci (furrows) with a lattice-like connection between adjacent furrow lines and uniform brown coloration throughout. No ridge pigmentation is identified.

What is the most likely dermoscopic pattern, and does this lesion require excision?

Lattice-like pattern (benign variant of parallel furrow pattern)

The lattice-like pattern is a recognized benign variant of the parallel furrow pattern in which pigment lines along the sulci are connected by thin bridging lines crossing the ridges, creating a lattice or grid appearance. The key reassuring features are: pigment is confined to the furrows (not the ridges), the pattern is symmetric and regular, and coloration is uniform. This pattern does not require excision but should be documented with dermoscopic photography for baseline comparison, particularly given its location on the weight-bearing sole where the lattice-like pattern is most commonly found.

The malignant dermoscopic patterns on volar skin are extensively covered in Chapter 8d. The key patterns are summarized here.

4.4.1 Parallel Ridge Pattern (PRP)

The hallmark of acrolentiginous melanoma. Linear pigmentation located predominantly on the ridges.

• Specificity: 99%
• Sensitivity: 86%
• Positive predictive value: 84%

Characteristics in melanoma in situ: Typically displays only tan-to-brown lines without other colors or visible structures.

Characteristics in invasive melanoma: Pigmentation on the ridges will rarely be the only feature; additional features such as multiple colors, irregular dots/globules, and streaks are usually present.

Exceptions -- Benign conditions displaying PRP:

• Ethnic pigmentation in darker-skinned patients
• Peutz-Jeghers syndrome
• Laugier-Hunziker syndrome
• Chemotherapy-induced volar pigmentation
• Exogenous dye
• Subcorneal hemorrhage (blood)
• Congenital nevi (occasionally)

4.4.2 Diffuse Pigmentation with Variable Shades of Brown

The second most common pattern in ALM. Structureless diffuse pigmentation involving both ridges and furrows, displaying various shades of brown.

4.4.3 Serrated Pattern

Projections (similar to streaks) at the edge of the tumor, occasionally encountered in ALM.

4.4.4 Atypical Fibrillar Pattern (Type B)

Fibrillar lines with increased variability in color (including gray) and thickness, distributed in a disorganized manner. On the palms, any fibrillar pattern should be considered atypical. On the soles, only the irregular (type B) fibrillar pattern is considered suspicious.

4.4.5 Milky-Red Pattern

Homogeneous reddish/whitish coloring, mainly seen in thicker melanomas with a vascularized nodular component.

4.4.6 Multicomponent Pattern

Multiple patterns present focally within the lesion, including:

• Focal parallel ridge pattern (often at the periphery)
• Structureless diffuse pigmented areas with multiple colors (brown, red, blue-white, black)
• Irregular dots and globules
• Streaks (serrated edge)
• Irregular blotches
• Blue-white veil
• Regression structures
• Atypical vessels
• Abrupt cutoff of pigment at the periphery

4.4.7 ALM with Focal Benign Patterns

Melanoma on volar skin may display patterns associated with nevi (parallel furrow, lattice-like) focally, but the rest of the lesion will display malignant patterns. Malignant patterns trump benign patterns. The entire lesion surface must be searched for malignant features before concluding a lesion is benign.

4.4.8 Size Matters

Most acquired nevi on volar skin are under 7 mm in greatest diameter. Acquired melanocytic lesions on volar skin greater than 7 mm should raise suspicion for melanoma, independently of the dermoscopic pattern.

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Check Your Understanding

What variants of the parallel furrow pattern exist, and are they all considered benign?

Variants include the lattice-like pattern (cross-hatched lines in the sulci), the fibrillar pattern (fine oblique parallel lines), and the crista dotted pattern (dots on the ridges with lines in the furrows). All variants are considered benign. The lattice-like pattern is the second most common benign acral pattern after the classic parallel furrow pattern.

Trauma-induced subcorneal blood often presents with a parallel ridge pattern, mimicking melanoma. Understanding the mechanism and distinguishing features is critical.

4.5.1 Mechanism

Blood within the skin tracks along the path of least resistance, which happens to be adjacent to the eccrine duct. Since the eccrine duct opens on the ridge, blood sequesters on the ridges. Initially, blood appears as globular structures ("pebbles on the ridges"). These focal blood spots fuse, resulting in the formation of a parallel ridge pattern.

4.5.2 Color

Depending on the oxidative state of hemoglobin, the pigment may be reddish, bluish, purple, black, brownish, or rust-colored.

4.5.3 Distinguishing Features from Melanoma

Feature	Subcorneal Hemorrhage	Melanoma
Peripheral pigment	Ends abruptly at the edge	Tends to fade toward the periphery
Cracks	Present (dried blood cracks visible on dermoscopy)	Absent
Color	Reddish, rust, or purple hues	Brown to black, may include blue-white
Scraping test	Paring down the stratum corneum with a scalpel removes the blood, confirming the diagnosis	Pigment cannot be removed
History	Often identifiable trauma	No trauma history, or de novo lesion
Morphology	"Pebbles on the ridges" (globular blood spots on ridges)	Linear continuous pigmentation on ridges

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Key Takeaways

• The parallel ridge pattern (pigment on dermatoglyphic ridges) has the highest sensitivity and specificity for acral melanoma of any single dermoscopic criterion.
• Eccrine duct openings (white dots on ridges visible under magnification) help determine whether pigment is on ridges (malignant) or in furrows (benign).
• Any acral lesion showing parallel ridge pattern should be biopsied regardless of size or clinical appearance, as early acral melanoma is often clinically subtle.

Angiomas, nevus flammeus, and hemangiomas on volar skin display two recurrent dermoscopic patterns:

1. Red dots/globules arranged linearly along each side of the ridge with sparing of the eccrine openings. This produces the double red-dotted parallel ridge pattern, which results from clusters of vessels in the papillary dermis located on both sides of the crista intermedia.
2. Regular lacunae situated on the ridges with sparing of the furrows. Red-to-maroon lacunae are diagnostic of angiomas/hemangiomas.

4.6.1 Differentiating Benign Vascular Lesions from Amelanotic ALM

Both benign vascular lesions and amelanotic ALM display red dots (vessels) on the ridges. The key distinction:

• Benign vascular lesions: Red dots/globules are oriented in regular, parallel lines on either side of the ridge (double red-dotted parallel ridge pattern).
• Amelanotic ALM: Vessels are distributed randomly along the ridges, without the regular double-line arrangement.

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Check Your Understanding

How should pigmented lesions on the non-glabrous (hairy) portions of the feet and hands be evaluated?

Non-glabrous acral skin (dorsal hands and feet, lateral digits) lacks dermatoglyphics and should be evaluated using standard dermoscopic criteria rather than acral-specific patterns. The parallel ridge/furrow distinction does not apply to these areas. Standard features like pigment network, globules, and streaks should be assessed as on any other body site.

It is not uncommon to encounter nevi on volar skin that manifest more than one benign pattern (e.g., double line furrow pattern on one side and double dotted line furrow pattern on another). Lesions manifesting more than one of the classic benign patterns are classified as benign in the acral diagnostic algorithm. These combination patterns do not indicate malignancy as long as all component patterns are recognized benign variants.

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Clinical Scenario

A 62-year-old man presents with a 9 mm pigmented lesion on his right great toe pad that has darkened over the past 6 months. Dermoscopy shows diffuse brown-to-black pigmentation predominantly located on the ridges (sulcus-free areas) with irregular dots and a focal area of blue-white veil. The parallel ridge pattern is clearly identified.

What is the significance of the parallel ridge pattern, and what is the appropriate management?

Acrolentiginous melanoma (parallel ridge pattern)

The parallel ridge pattern (PRP) -- pigmentation located on the ridges of volar skin -- is the dermoscopic hallmark of acrolentiginous melanoma, with a specificity of 99% and sensitivity of 86%. In this case, the PRP is accompanied by additional concerning features: irregular dots/globules and blue-white veil, which indicate an invasive component. Immediate excisional biopsy is mandatory. The additional features beyond simple ridge pigmentation suggest progression beyond melanoma in situ. While benign conditions such as subcorneal hemorrhage or ethnic pigmentation can occasionally produce ridge pigmentation, the combination of PRP with multicomponent features in this clinical context is highly suspicious for ALM.

The BRAAFF checklist (Lallas et al., 2015) provides a structured scoring system for evaluating volar melanocytic lesions.

4.8.1 Scoring Criteria

Positive criteria (anywhere within the lesion):

Letter	Criterion	Score
B	Irregular Blotch	+1
R	Parallel Ridge pattern	+3
A	Asymmetry of structures	+1
A	Asymmetry of colors	+1

Negative criteria (anywhere within the lesion):

Letter	Criterion	Score
F	Parallel Furrow pattern	-1
F	Fibrillar pattern	-1

4.8.2 Interpretation

A total score of 1 or more indicates the lesion should be considered suspicious for acral melanoma and warrants biopsy or referral.

4.8.3 Application Notes

• The parallel ridge pattern carries the highest positive weight (+3), reflecting its strong association with ALM.
• The presence of a parallel furrow pattern or fibrillar pattern provides negative (protective) scores, reflecting their benign associations.
• Context (age, size, location) should still be considered alongside the BRAAFF score.

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Key Takeaways

• Subcorneal hemorrhage (blood in the stratum corneum) on acral skin shows red-brown globules that track distally with skin turnover and can be confirmed by dermoscopic follow-up at 2-4 weeks.
• Ethnic/racial melanosis on the soles shows regular parallel furrow pattern bilaterally and does not require biopsy but should be documented for baseline monitoring.
• Pressure-related changes on the soles can distort dermatoglyphic patterns and create pseudoridges; examining the lesion without pressure and comparing with the contralateral foot helps clarify the pattern.

The comprehensive algorithm for evaluating volar melanocytic lesions follows a stepwise approach:

Step 1 -- Identify the pattern:

• Determine whether the lesion displays a recognizable benign pattern (parallel furrow, lattice-like, typical fibrillar, globular, reticular, homogeneous) or a malignant pattern (parallel ridge, diffuse irregular pigmentation, multicomponent).

Step 2 -- Classify and act:

• Classic benign pattern(s) present: Classify as benign. Multiple benign patterns within one lesion are still benign.
• Classic malignant pattern present: Biopsy/excise. Remember that malignant patterns trump focal benign patterns.
• Nontypical pattern (no classic benign or malignant pattern): Proceed to Step 3.

Step 3 -- Evaluate nontypical lesions by context:

• Lesion diameter greater than 7 mm: Consider biopsy regardless of pattern.
• Lesion diameter 7 mm or less: Evaluate for asymmetry, more than two colors, blue-white structures, vessels, dots, streaks, or abrupt edges. Consider clinical context (age, location, history). If suspicious features are present, biopsy. If absent, consider digital dermoscopy monitoring.

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The distribution and morphology of acral nevi vary with patient age and anatomic location on the foot:

Factor	Pattern Association
Congenital nevi	Peas-in-a-pod pattern, crista dotted pattern, globular pattern
Acquired nevi (typical)	Parallel furrow pattern, lattice-like pattern
Arch of foot	Lattice-like pattern most common; reticular pattern occasionally
Weight-bearing sole	Fibrillar pattern (type A) most common
Between arch and weight-bearing	Parallel furrow pattern most common
Palms	Parallel furrow variants; lattice-like

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Weight-bearing forces and frictional pressure significantly influence the appearance of acral lesions:

• The fibrillar pattern is itself a pressure artifact: lateral shearing forces on the stratum corneum cause melanin columns to grow obliquely, converting an underlying parallel (furrow or ridge) pattern into a fibrillar pattern.
• Oblique-view dermoscopy can reverse this effect, revealing the true underlying pattern.
• Contact dermoscopy with counter-pressure: Applying downward and horizontal pressure opposite to normal frictional forces can transiently convert the fibrillar pattern back into a parallel pattern.
• "PlayStation purpura" and "black heel" represent pressure-induced subcorneal hemorrhage that mimics the parallel ridge pattern.

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Several nonmelanocytic conditions can mimic melanocytic lesions on volar skin:

Subcorneal Hemorrhage (Hematoma)

• Discussed in detail in Section 4.5.
• Key clue: "Pebbles on the ridges," abrupt peripheral cutoff, rust/purple color, cracks, positive scraping test.

Viral Wart (Verruca)

• Dermoscopy: Frog-spawn pattern (thrombosed capillaries appearing as red-black dots within a papillomatous surface), interrupted dermatoglyphics.
• Disruption of normal sulci/cristae pattern distinguishes warts from melanocytic lesions.

Corn/Callus

• Dermoscopy: Homogeneous yellowish structureless area, preservation of dermatoglyphics (unlike warts), absence of melanin pigmentation.
• Central translucent core in corns.

Tinea Nigra

• Dermoscopy: Superficial wispy light brown pigmentation with a spiculated or nondescript pattern that does not follow the furrow-ridge architecture of melanocytic lesions. No parallel furrow or parallel ridge pattern.
• Pigment can be removed with scraping (superficial fungal infection in the stratum corneum).

Drug-Induced (Chemotherapy) Pigmentation

• Dermoscopy: Can display a parallel ridge pattern or diffuse homogeneous pigmentation.
• Clinical context: bilateral involvement, temporal correlation with drug initiation, multiple digits affected.
• Commonly associated with hydroxyurea, cyclophosphamide, doxorubicin, and other chemotherapeutic agents.

Ethnic/Racial Pigmentation

• In darker-skinned individuals, physiologic pigmentation can display a parallel ridge pattern.
• Clinical context: bilateral, symmetric, multiple locations, stable over time.

Laugier-Hunziker Syndrome / Peutz-Jeghers Syndrome

• Can display parallel ridge pattern.
• Clinically: multiple small brownish macules on multiple fingers and/or lips; systemic features in Peutz-Jeghers (GI polyps).

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Key Takeaways

• The acral algorithm begins with identifying dermatoglyphic patterns: furrow pattern = benign, ridge pattern = biopsy, irregular/non-pattern = further evaluation.
• Multi-component pattern on acral skin (combining ridge pigment, irregular diffuse pigmentation, and regression) strongly suggests melanoma and warrants complete excision.
• Serial acral dermoscopy is appropriate for benign-pattern lesions but inappropriate for lesions with any ridge pigmentation, irregular diffuse pigmentation, or multi-component features.