Malignant melanoma in situ arising in the nail unit of a child

Pediatric Nail Disorders

Background

Pediatric nail disorders encompass a broad range of conditions. This article aimed to consolidate current knowledge on pediatric nail disorders to enhance diagnostic proficiency and clinical management among healthcare professionals.

Summary

Pediatric nail disorders present a diagnostic challenge due to their diverse nature. Non-syndromic congenital nail disorders encompass various anomalies such as anonychia/hyponychia, congenital malalignment of the great toenail, and racket thumbs, each with distinct clinical presentations and genetic associations. Syndromic congenital nail disorders, often part of complex syndromes, are characterized by unique features and associated abnormalities. Acquired nail diseases in children, like Beau's lines and onychomadesis, typically result from trauma or infection, while melanonychia, although rare in children, requires careful monitoring for potential malignant alterations, with consideration for biopsy in cases with concerning features.

Key Messages

(1) Pediatric nail disorders may pose diagnostic challenges and require a comprehensive understanding of nail anatomy and development. (2) Congenital nail disorders encompass isolated anomalies and syndromic associations, necessitating thorough evaluation for associated systemic conditions. (3) Acquired nail diseases may indicate underlying trauma or systemic illness and require careful assessment.(4) Melanonychia in children requires ongoing monitoring and evaluation, emphasizing the importance of consistent follow-up and histopathological examination when necessary.

Clinical and Histopathological Investigation of Pediatric Melanonychia: A Single-Center Retrospective Case Series

HYPOTHESIS

The natural history of pediatric melanonychia and the necessity of biopsy for ruling out melanoma are debated in the literature. We hypothesize that there is a low rate of malignant nail pathology among pediatric patients undergoing nail bed biopsy for melanonychia.

METHODS

We performed a retrospective chart review of 54 pediatric patients (age <18 years) at a single institution who presented with melanonychia and underwent nail bed biopsy from 2007 to 2022. Data points collected included patient demographics, medical history, physical exam findings, pathology reports, and clinical photos. Univariate and multivariate analyses were performed to assess for risk factors associated with high-risk pathology findings.

RESULTS

The average age of melanonychia onset was 5.5 years (SD 4.4). The average age of first biopsy was 7.8 years (SD 4.3). On physical exam, 27 patients had at least four features concerning for melanoma (asymmetry, border irregularity, color heterogeneity, diameter > 1/3 of nail, evolving color, evolving diameter, Hutchinson's sign). The most common pathology diagnoses were melanocytic nevus (35%), atypical intraepidermal melanocytic proliferation (AIMP) with benign features (24%), subungual lentigo (22%), and AIMP with concerning features (17%). There were no cases of melanoma in situ or invasive malignant melanoma. On multivariate regression, the only significant risk factor associated with more concerning pathology (AIMP with concerning features) was the calendar year in which biopsy was performed (coefficient = -0.34, P = 0.016). There was no association between physical exam features and high-risk pathology. Twelve patients had surgical re-excision of the lesion, 6 of which were due to incomplete excision of AIMP with concerning features and 6 of which were due to recurrence.

CONCLUSIONS

Our case series did not find any cases of melanoma in situ or malignant melanoma arising from pediatric melanonychia. Atypical intraepidermal melanocytic proliferation with concerning features was associated only with the year in which the biopsy was performed, which may reflect the improved understanding of pediatric melanonychia as often benign despite concerning features on pathology. The decision to perform a nail matrix biopsy in pediatric melanonychia should be based on a collaborative discussion between the patient's parents, dermatologist, and plastic surgeon.

Melanoma in children: A systematic review and individual patient meta-analysis

The current evidence on paediatric melanoma is heterogeneous, especially regarding the prognosis of different histological subtypes. We sought to systematically review the evidence on paediatric melanoma, highlighting the major sources of heterogeneity and focusing on available data on single patients. A systematic search was performed from 1948 to 25 January 2021. Only studies reporting at least one case of cutaneous melanoma in patients aged ≤18 years were included. Unknown primary and uncertain malignant melanomas were excluded. Three couples of authors independently performed title/abstract screening and two different authors reviewed all the relevant full texts. The selected articles were manually cross-checked for overlapping data for qualitative synthesis. Subsequently data on single patients were extracted to perform a patient-level meta-analysis. PROSPERO registration number: CRD42021233248. The main outcomes were melanoma-specific survival (MSS) and progression-free survival (PFS) outcomes. Separate analyses were done of cases with complete information on histologic subtype, focusing on superficial spreading (SSM), nodular (NM) and spitzoid melanomas, as well as of those classified as de-novo (DNM) and acquired or congenital nevus-associated melanomas (NAM). The qualitative synthesis covered 266 studies; however, data on single patients were available from 213 studies including 1002 patients. Among histologic subtypes, NM had a lower MSS than both SSM and spitzoid melanoma, and a lower PFS than SSM. Spitzoid melanoma had a significantly higher progression risk than SSM and trended toward lower mortality. Focusing on nevus-associated status, DNM demonstrated better MSS after progression than congenital NAM, and no differences were highlighted in PFS. Our findings describe the existence of different biological patterns in paediatric melanoma. Specifically, spitzoid melanomas demonstrated intermediate behaviour between SSM and NM and showed a high risk of nodal progression but low mortality. This raises the question of whether spitzoid lesions are being over-diagnosed as melanoma in childhood.

Subungual Melanocytic Lesions in Pediatric Patients

The study of subungual melanocytic lesions can present challenges because of the clinical and histologic characteristics of the nail unit and the difficulty of performing nail biopsies and processing specimens. These lesions can be even more challenging in children due to differences in clinical and epidemiological profiles between the adult and pediatric populations. Many of the clinical features of subungual melanocytic lesions that would raise alarm in an adult do not have the same implications in children. Consensus is also lacking on when a nail biopsy is needed to rule out malignancy in the pediatric setting. In view of these considerations and the rarity of subungual melanoma in childhood, the recommended approach in most cases is a watch-and-wait strategy. Subungual melanocytic lesions in children may also show atypical histopathologic features that are not necessarily associated with aggressive behavior. Subungual melanoma is very rare in childhood, with just 21 cases described to date. None of the patients developed visceral metastasis or died as a result and the diagnosis was controversial in many of the cases. Considering the above and the significantly higher frequency and particular characteristics of longitudinal melanonychia with a benign etiology in children, subungual melanocytic lesions should be managed differently in this setting than in adults. In most cases, a watch-and-wait approach is the most appropriate strategy.

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.

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

AIMS

Longitudinal melanonychia in paediatric patients often represents a difficult diagnostic challenge, and studies emphasising its clinical and histopathological features are limited due to its low incidence in childhood.

METHODS AND RESULTS

We retrospectively analysed 35 paediatric cases identified by excision specimens on their clinicopathological features, and performed fluorescence in-situ hybridisation on 13 available cases. Fingernails (77.1%) were more likely to be affected. Total melanonychia and Hutchinson's sign were observed in 10 (28.6%) and 14 (40.0%) cases, respectively. Nail dystrophy at diagnosis was present in five cases. After complete excision of the lesions, four patients relapsed during follow-up (mean = 38 months). Seventeen cases were diagnosed as lentigines and 18 as naevi, among which 11 cases were categorised as lentigines/naevi with atypical melanocytic hyperplasia. Mild-to-moderate nuclear atypia, confluency of melanocytes, focal pagetoid spread and peri-ungual skin involvement were found in 25.7% (9 of 35), 40.0% (14 of 35), 40.0% (14 of 35) and 40.0% (14 of 35) of cases, respectively. Thirteen cases tested by fluorescence in-situ hybridisation showed no copy number aberration at the probed loci. There was a statistically significant difference in the following features between patients aged less and more than 10 years (P < 0.05): cytomorphology, mild-to-moderate nuclear atypia, confluency of melanocytes, focal pagetoid spread and melanocyte count.

CONCLUSIONS

Some concerning clinicopathological characteristics, which are signs indicative of melanoma in adults, are not uncommon in paediatric longitudinal melanonychia, especially in patients aged ≤ 10 years. Owing to the extremely low incidence of melanoma in paediatric longitudinal melanonychia, in most circumstances a more conservative clinical management strategy should be adopted.

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.

Childhood longitudinal melanonychia: case series from Poland

Introduction

Longitudinal melanonychia (LM) is characterized by a tan, brown or black longitudinal streak within nail plate caused by the presence of melanin. LM is relatively common in dark-skinned population, infrequent in Caucasian population, and rare in children.

Aim

We report epidemiological, clinicopathological and dermoscopic analysis of 8 cases of childhood LM from Poland, which is the largest series in the Central and Eastern European population.

Material and methods

Three hundred and forty-eight patients presenting with various nail pigmentation (in 2010-2016) were analysed. 72 cases of LM have been identified, including 8 cases of childhood LM (< 16 years of age), which were included in further analysis.

Results

Seven patients were boys and one girl, with mean age of 9 years (range: 6-13). More than a half (n = 5) presented skin phototype II. The most common location of melanonychia was the first left fingernail. Dermoscopy revealed heterogeneity of longitudinal lines colour in 5 cases. The irregularity of longitudinal line thickness in 5 cases and irregularity of parallelism in 5 cases was observed. Histopathological evaluation was performed in 4 patients, in 3 cases it revealed the presence of nail matrix nevus, in one case the presence of melanocytic proliferation of the lentiginous pattern along the dermoepidermal junction.

Conclusions

Despite the fact that melanoma was not recognised in any case, such a possibility should always be considered as the cause of LM, even in the paediatric population. Dermoscopy seems to be useful in patient follow-up and management.

Childhood subungual melanoma in situ in diffuse nail melanosis beginning as expanding longitudinal melanonychia

We report a rare childhood occurrence of melanoma in situ presenting as diffuse nail pigmentation resulting from expanding longitudinal melanonychia, and discuss factors that should come into play when considering a possible nail matrix biopsy.

Two cases of unusual acral melanocytic tumors: illustration of molecular cytogenetics as a diagnostic tool

The differential diagnosis between benign Spitz nevus and malignant melanoma may present considerable difficulties in some cases. Here we report 2 unusual melanocytic tumors with spitzoid features developing in acral sites of Japanese patients to illustrate the use of comparative genomic hybridization (CGH) to classify these lesions. Case 1 was a 12-mm-thick, >2 cm-diameter nodule on the sole of a 37-year-old man. Case 2 was a subungual tumor of the left index finger in a 13-year-old boy. CGH showed absence of chromosomal aberrations in case 1 and multiple aberrations in case 2, including focused amplification as previously described in acral melanomas. Case 1 was free of disease after 2.5 years of follow-up, whereas case 2 developed lymph node metastasis. We conclude that molecular techniques such as CGH can be of diagnostic help in the classification of histologically ambiguous lesions.

Nail apparatus melanoma

Nail apparatus melanoma is a relatively rare variant of melanoma with a disproportionately high mortality when compared with melanoma elsewhere. The aetiology and natural history remain poorly understood. There is no clear epidemiological association with race, skin type or sun exposure. Universally accepted clinical and histological criteria for the diagnosis of early nail apparatus melanoma have not been defined. The two cardinal clinical signs are melanonychia striata and Hutchinson's sign. These are useful but not pathognomonic of melanoma. Diagnostic delay is frequent and patients commonly have advanced disease at the time of diagnosis. Surgical excision is advocated for treatment of stage I disease; however, the most appropriate re-excision margins, including the level of amputation where required, have not been determined. Early diagnosis and excision of the tumour is the only treatment known to increase survival. Adjuvant systemic chemotherapy, isolated limb perfusion, and routine elective lymph node dissection have been used, but no survival benefit has been demonstrated.

Nail melanoma: a review of the literature with recommendations to improve patient management

In this review, the current state of knowledge concerning nail melanoma is summarized. The pathogenesis, histological findings, clinical presentation, treatment and prognosis of this rare form of cutaneous melanoma are discussed. Important clinical clues to the early diagnosis of nail melanoma are highlighted and recommendations to improve the management of patients are suggested.

Longitudinal melanonychia in children: a clinical and histopathologic study of 40 cases

OBJECTIVE

Very little has been published on longitudinal melanonychia in children. Our objective was to determine the nature of melanocytic lesions in pediatric patients with longitudinal or total melanonychia and to look for correlations between clinical and histologic features.

METHODS

All patients younger than 16 years of age with longitudinal or total melanonychia who were evaluated at our nail disorder outpatient clinic between September 1993 and September 1996 were included. The clinical and histologic features of the nail condition were determined in each case.

RESULTS

Forty patients were included. The final diagnosis was nevus in 19 cases (junctional in 17 cases and compound in 2), lentigo in 12 cases, and functional longitudinal melanonychia in 9. The latter corresponded to a hyperpigmentation caused by melanocytic activation with no increase in the number of melanocytes. None of the patients had melanoma. Appearance within the first year of life, periungual pigmentation, and total melanonychia were consistent features in patients with melanocytic hyperplasia (lentigo or nevus). Early onset of a dark broad lesion in a white patient was typical of melanocytic hyperplasia, although none of these features were pathognomonic.

CONCLUSION

Benign melanocytic hyperplasia (lentigo or nevus) was the cause of 77.5% of cases of longitudinal melanonychia in our overall pediatric population and of 85% of cases in the subset of white patients. All the remaining cases of longitudinal melanonychia were the result of melanocytic activation.