Clinicopathological diversity and outcome of longitudinal melanonychia in children and adolescents: analysis of 35 cases identified by excision specimens

Melanoma-like features in pediatric longitudinal melanonychia: A systematic review and meta-analysis

BACKGROUND

Pediatric longitudinal melanonychia (LM) can exhibit atypical features that mimic red-flag signs for subungual melanoma in adults and lead to diagnostic uncertainty. Nail biopsy may be unnecessary if clinical inspection and dermoscopy suggest a benign nature.

METHODS

We searched PubMed and Embase from inception to February 2023 for studies of any design reporting either the number or proportion of clinical and dermoscopic features in at least five children (≤18 years) with LM. Non-English articles, reviews, and abstracts were excluded. We performed a systematic review and meta-analysis to collate all existing data.

RESULTS

A total of 1218 articles were screened and 24 studies with 1391 pediatric patients were included. Nevus was the most common diagnosis (86.3%). The most prevalent sites were fingernails (76.2%) and first digits (45.4%). Pooled proportions of common features were: dark-color bands (69.8%), multi-colored bands (47.6%), broad bandwidth (41.1%), pseudo-Hutchinson sign (41.0%), irregular patterns (38.1%), Hutchinson sign (23.7%), dots and globules (22.5%), nail dystrophy (18.2%), and triangular sign (10.9%). Outcomes included progression (widening or darkening, 29.9%), stability (23.3%), and spontaneous regression (narrowing or fading, 19.9%). Only eight cases of subungual melanoma in situ were reported, and no invasive melanomas were identified.

CONCLUSION

Although atypical characteristics are common in pediatric LM, the probability of malignant transformation is exceedingly low. Appropriate evaluation and management of pediatric LM includes careful clinical and dermoscopic inspection with attention to benign features followed by long-term interval follow-up.

Acral Melanocytic Neoplasms: A Comprehensive Review of Acral Nevus and Acral Melanoma in Asian Perspective

Acral melanocytic neoplasms, including acral melanocytic nevus and acral melanoma, are common melanocytic lesions in Asian populations. Both lesions occur on the volar surface of the hands and feet, and on nail units. Acral melanocytic nevi occur on the arch area of the sole, whereas acral melanomas frequently occur on weight-bearing areas of the sole, and on the fingernails. Therefore, the development of acral melanoma may be associated with chronic pressure, physical stress, or trauma. Dermoscopy is a useful adjunctive diagnostic tool for differential diagnosis. Acral melanocytic nevus is characterized by a parallel furrow pattern, whereas acral melanoma has a parallel ridge pattern. Genetic alterations are also different between the two types of lesion. BRAF and NRAS mutations are common in acral melanocytic nevus, whereas acral melanoma shows lower rates of KIT, NF1, BRAF, and NRAS mutations and remarkable copy number variations in genes such as CCND1, CDK4, hTERT, PAK1, and GAB2. Sentinel lymph node biopsy is important for staging and prognosis. Contemporary treatments for melanoma include targeted therapy for mutations and immunotherapy, such as anti-PD1 inhibitors.

An Evidence-Based Approach to Pediatric Melanonychia

Melanonychia including melanonychia striata in children poses a diagnostic dilemma. Atypical clinical features often raise the possibility of malignancy, and a nail unit biopsy may be recommended. Commensurate with atypical clinical features, the histopathology may also appear alarming. However, accumulating data illustrate that most cases of melanonychia striata are benign and suggest that an alternate approach is often warranted for pediatric patients. Herein, we review the existing data regarding pediatric melanonychia striata and offer an evidence-based approach to its evaluation and management.

Subungual Melanocytic Lesions: Key Clinical and Pathologic Concepts and Biopsy Techniques

Both dermatologists and pathologists sometimes find daunting the evaluation of melanonychia (especially subungual melanocytic lesions) because of the fear of performing nail surgery due to the risk of dystrophy, difficulties processing and interpreting nail biopsy specimens, and a general lack of experience in the field. Nevertheless, mastery of nail biopsy techniques, correct processing and orientation of specimens, and familiarity with the histologic particularities of the nail apparatus can attenuate the undoubted complexity and facilitate the tasks involved. Longitudinal excision is the biopsy technique that ensures the simplest histologic interpretation, and it is associated with a low risk of nail dystrophy when performed correctly. Clinical and epidemiological data are crucial. Subungual melanoma in childhood, for instance, is very rare and even lesions with atypical clinical and/or histologic features are probably benign. The presence of suprabasal melanocytes and other findings that would suggest malignancy at other sites are considered normal in the nail apparatus. Subungual melanoma shows a lentiginous pattern in the early stages of disease, and detection of an inflammatory infiltrate accompanying atypical lentiginous subungual lesions would appear to be one of the first diagnostic findings.

Subungual Melanocytic Lesions: Key Clinical and Pathologic Concepts and Biopsy Techniques

Both dermatologists and pathologists sometimes find daunting the evaluation of melanonychia (especially subungual melanocytic lesions) because of the fear of performing nail surgery due to the risk of dystrophy, difficulties processing and interpreting nail biopsy specimens, and a general lack of experience in the field. Nevertheless, mastery of nail biopsy techniques, correct processing and orientation of specimens, and familiarity with the histologic particularities of the nail apparatus can attenuate the undoubted complexity and facilitate the tasks involved. Longitudinal excision is the biopsy technique that ensures the simplest histologic interpretation, and it is associated with a low risk of nail dystrophy when performed correctly. Clinical and epidemiological data are crucial. Subungual melanoma in childhood, for instance, is very rare and even lesions with atypical clinical and/or histologic features are probably benign. The presence of suprabasal melanocytes and other findings that would suggest malignancy at other sites are considered normal in the nail apparatus. Subungual melanoma shows a lentiginous pattern in the early stages of disease, and detection of an inflammatory infiltrate accompanying atypical lentiginous subungual lesions would appear to be one of the first diagnostic findings.