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Onychoscopy, Pigmented & Unpigmented Nail Tumors

Longitudinal melanonychia stratification + the unpigmented nail-unit tumor algorithm, without these, nail biopsy is a guessing game.

By Dr. Yehonatan KaplanPublished Updated

In brief

The nail unit is unforgiving: any pigmented streak triggers a melanoma rule-out, and most benign streaks look identical to early subungual melanoma at first glance. Onychoscopy provides four cardinal rules, uniform vs irregular lines, parallelism, Hutchinson sign extension, and loss of the linear pattern, that stratify pigmented lesions efficiently. Unpigmented tumors are an entirely different problem solved by vessel morphology and tumor architecture.

Clinical content

01Longitudinal melanonychia (LM): regular, parallel, uniform-thickness brown lines on a brown background = benign. Irregularity in width, color, parallelism = biopsy.

02Hutchinson sign: pigmentation extending onto periungual skin = subungual melanoma until proven otherwise. Pseudo-Hutchinson (subungual hematoma seen through translucent cuticle) is the main mimic.

03Subungual hematoma: rounded purplish-red lesion, peripheral fading globules; moves distally with nail growth. Dermoscopy + waiting 2-3 months > biopsy.

04Unpigmented nail unit tumors (F042 #2): use vessel morphology, onychopapilloma shows linear hyperkeratosis with red-dot vessels at distal edge; squamous cell carcinoma has dotted/glomerular vessels with onycholysis; glomus tumor has a violaceous bluish patch with palpable point tenderness.

05Biopsy technique: longitudinal nail matrix biopsy via the modified Haneke approach for matrix lesions; tangential shave for distal/lateral lesions to preserve nail growth.

Key dermoscopic features

Regular parallel lines (uniform brown)
Benign LM (lentigo, drug, ethnic).
Irregular lines (variable width/color)
Subungual melanoma.
Loss of parallelism
Subungual melanoma.
Hutchinson sign
Pigment extending to periungual skin, melanoma.
Pseudo-Hutchinson
Hematoma seen through cuticle, benign mimic.
Round purplish-red blotches
Subungual hematoma.
Globules at periphery
Resolving hematoma.
Linear hyperkeratosis with distal red dots
Onychopapilloma.
Dotted/glomerular vessels + onycholysis
Subungual SCC.
Bluish-violaceous patch + tender point
Glomus tumor.

High yield clinical points10 pearls in 4 groups

Recognition & pattern analysis

3 points
1
Hematoma migrates distally. Track a 'nail spot' over weeks; hematoma moves with nail growth, melanoma does not.
2
Onychopapilloma signature. Linear nail-bed hyperkeratosis + red dots at distal edge + splinter hemorrhages; benign and ablate-able if symptomatic.
3
Pediatric LM is usually benign. In children, LM is overwhelmingly benign, observe with photographs unless aggressive features develop.

Diagnostic criteria & thresholds

1 point
1
Glomus = pinpoint pain. Bluish patch + Love's sign (pinprick pain) + cold sensitivity, MRI/dermoscopy confirm.

Pitfalls & mimics

2 points
1
Hutchinson > all other features. Pigment on periungual skin is melanoma until proven otherwise; do not be reassured by the rest of the lesion's features.
2
Pseudo-Hutchinson exists. Subungual hematoma can show through a translucent cuticle and mimic Hutchinson; check by waiting 2-3 months for distal migration.

When to biopsy

4 points
1
Parallelism is the gatekeeper. Regular, parallel, uniform brown lines on brown background = benign LM. Any irregularity = biopsy.
2
Bands ≥3 mm warrant biopsy (ABCDEF rule). Pigmented bands ≥3 mm in adults trigger matrix biopsy under the ABCDEF rule (Levit 2000). Width is the B in ABCDEF; a band approaching or exceeding 3 mm raises melanoma probability enough to justify histologic confirmation.
3
SCC of the nail unit. Onycholysis + dotted/glomerular vessels + hyperkeratosis with verrucous surface, biopsy proximal nail-bed.
4
Biopsy preserves growth. Tangential shave or modified Haneke matrix biopsy preserves nail-plate continuity better than longitudinal full-thickness biopsy.

Lectures covering this topic7 lectures

AAD 2026F042 · #02
Dermoscopy of Nail Unit Unpigmented Tumors
Luc Thomas, MD, PhD
AAD 2026F095 · #01
Onychoscopy
Onychoscopy Faculty (AAD 2026)
AAD 2026U003 · #03
How to Incorporate RCM into a Busy Practice
Margaret Oliviero, ARNP and Harold Rabinovitz, MD
Excellence (main)DE-MAIN · #06
Acral and Nail Lesions
G. Argenziano and A. Lallas
Excellence PediatricDE-PED · #02
Miscellaneous Pediatric Lesions
Vincenzo Piccolo and Giuseppe Argenziano
Academy 2025ACAD25 · #13
Onychoscopy
Ashfaq A. Marghoob
ADM 2025ANNUAL13 · #21
Onychoscopy
Ashfaq A. Marghoob, MD

Notable updates & conceptual milestones5 updates

Reflectance confocal microscopy of the nail bed

2023-2026

RCM through the nail plate is now feasible at major centers; helps avoid matrix biopsy in equivocal LM.

Standardized onychoscopy reporting

2024

AAD/IDS 2024 consensus on minimum dataset for nail dermoscopic reports, improves teledermoscopy referrals.

Modified Haneke for the digital era

2022-2025

Refined matrix biopsy techniques with intraoperative dermoscopy to preserve nail unit anatomy and reduce post-biopsy dystrophy.

Intra-operative onychoscopy after plate avulsion

2024

A 2024 systematic review of 19 studies (218 cases) defined intra-operative onychoscopy after nail plate avulsion as a useful biopsy-planning adjunct, directly visualizing matrix and bed structures across melanoma, glomus, SCC, and onychomatricoma.

Nail expert consensus on LM workflow

2025

A 2025 international nail expert consensus positions onychoscopy plus nail-clipping histopathology as first-line LM triage, reserving matrix tangential biopsy for suspicious cases and longitudinal excision for likely-invasive disease.

Bottom line

Longitudinal melanonychia stratification + the unpigmented nail-unit tumor algorithm, without these, nail biopsy is a guessing game.

10 clinical points · 5 recent updates · 9 references

Source content

AAD 2026 · F095 · #01

Onychoscopy

AAD 2026 · F042 · #02

Dermoscopy of Nail Unit Unpigmented Tumors

References

Sources cited in the lecture content or that underpin the clinical points above. Verify with primary sources before practice changes.

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