When is a biopsy indicated in pediatric patients with longitudinal melanonychia (longitudinal melanonychia)?

Biopsy Indications in Pediatric Patients with Longitudinal Melanonychia

Biopsy of longitudinal melanonychia in pediatric patients should be reserved for cases with specific high-risk features, as most cases in children are benign and unnecessary biopsies can lead to permanent nail dystrophy. 1, 2

Risk Assessment and Indications for Biopsy

High-Risk Features Requiring Biopsy:

• Rapid change in appearance or width of the band
• Band width >3mm or >50% of the nail plate
• Multicolored pigmentation (heterogeneous coloration)
• Granular pigmentation within the band
• Presence of Hutchinson's sign (pigmentation extending to periungual skin)
• Micro-Hutchinson's sign (pigmentation visible on dermoscopy but not clinically)
• Subungual hyperkeratosis
• Nail plate destruction or dystrophy
• Bleeding or pain in the affected nail
• Personal or family history of melanoma 1, 3

Lower-Risk Features (Observation Appropriate):

• Single uniform color (especially in darker-skinned children)
• Stable appearance over time
• Multiple nails affected
• Band width <3mm
• Presence of pseudo-Hutchinson's sign (optical illusion of periungual pigmentation)
• Zigzag pattern on dermoscopy (particularly in children) 4, 2

Biopsy Technique When Indicated

When biopsy is deemed necessary, the following approach should be used:

1. Nail matrix sampling is essential - The nail plate should be sufficiently removed to expose the underlying lesion, as melanoma arises in the nail matrix 1

2. Biopsy should be performed by a practitioner skilled in nail apparatus procedures due to the complexity of nail anatomy 1

3. Biopsy technique options:

   • Excisional biopsy is preferred when possible
   • Incisional biopsy is acceptable for larger lesions
   • The nail matrix should be adequately sampled 1

Special Considerations for Pediatric Patients

Age-Related Approach:

• Children with skin of color: Longitudinal melanonychia is extremely common (up to 77% prevalence in African Americans) and rarely malignant; observation is generally preferred over biopsy 5, 2

• Children <14 years: Conservative approach is warranted as subungual melanoma is exceedingly rare in this age group 1, 2

• Adolescents: Closer to adult protocols but still with more conservative approach than adults 1

Monitoring Recommendations:

• Regular clinical and dermoscopic follow-up every 3-6 months for concerning lesions not meeting immediate biopsy criteria
• Photography at each visit to document changes
• Consider dermoscopy to identify subtle changes 5, 3

Challenges and Pitfalls

• Diagnostic challenges: Histopathologic interpretation of pediatric nail biopsies can be difficult with poor inter-observer agreement among pathologists 2

• Procedural risks: Nail biopsies in children can result in permanent nail dystrophy and should be weighed against the extremely low incidence of subungual melanoma in this population 2

• Continuity of care: Consider social factors that may affect follow-up when deciding between observation and biopsy 5

• Referral recommendation: Children with concerning longitudinal melanonychia should be evaluated by dermatologists experienced in pediatric nail disorders 1, 6

By following these guidelines, clinicians can appropriately identify the rare cases requiring biopsy while avoiding unnecessary procedures in the majority of benign pediatric longitudinal melanonychia cases.