Melanonychia: the importance of dermatoscopic examination and of nail matrix / bed observation

Abstracts

Melanoníquia, do grego mélaina, negro, sombrio, resulta de uma deposição aumentada de melanina na lâmina ungueal originada a partir da matriz ungueal. Apresenta diversas causas, entre elas, o melanoma subungueal, por isso, seu diagnóstico etiológico torna-se essencial, devendo ser o mais precoce possível. Os autores apresentam dois pacientes com melanoníquias de natureza distinta e enfatizam o seu diagnóstico diferencial.

Biópsia; Lentigo; Melanoma; Unha

CASE REPORT

Melanonychia: the importance of dermatoscopic examination and of nail matrix / bed observation

Aline Perdiz de Jesus Bilemjian^I; Juan Piñeiro-Maceira^II; Carlos Baptista Barcaui^III; Francisco Burnier Pereira^IV

^IGraduate studies in Dermatology by the Instituto de Dermatologia Professor Rubem David Azulay (IDPA) of Santa Casa da Misericórdia do Rio de Janeiro – Rio de Janeiro (RJ), Brazil

IIPost-Doctoral studies in Dermatopathology at the Armed Forces Institute of Pathology (AFIP) - Washington, D.C. – USA Associate Professor – Department of Pathology of the Universidade Federal do Rio de Janeiro (UFRJ) – Rio de Janeiro (RJ), Brazil

IIIMSc and PhD in Dermatology – USP. Assistant Professor of the Melanocytic Lesions Outpatient Clinic - IDPA – São Paulo (SP), Brazil

IVPhD in Dermatology by the Universidade Federal do Rio de Janeiro (UFRJ). Chief Resident of the Melanocytic Lesions Outpatient Clinic – IDPA. Associate Prof. of PUC-RJ – Rio de Janeiro (RJ), Brazil

Mailing Address

ABSTRACT

Melanonychia, from the Greek mélaina, means black and is the result of an increased deposition of melanin on the nail plate, originating in the nail matrix. It may have different causes, including subungueal melanoma, making early etiologic diagnosis very important.

Keywords: Biopsy; Lentigo; Melanoma; Nail

INTRODUCTION

Melanonychia is the brown to black color of the nail plate.^1,2,3 According to some authors, all melanonychias are caused by deposition of melanin,^1,4 others also include in the definition the pigmentation produced by non melanocytic lesions, such as subungueal hematoma and onychomycosis.^2,3 There are countless etiologies, in which benign melanocytic activation (racial melanonychia), benign melanocytic hyperplasia (lentigo, melanocytic nevus) and melanoma are a few examples of melanocytic lesions that originate melanonychias. ² Early etiological diagnosis of this finding is very important, given that one of the causes is a rare malignant but aggressive neoplasm,.²

Two cases of melanonychia follow, one malignant and another benign. Epidemiological, clinical, dermatoscopic and histopathological aspects of the lesions are discussed, especially to differentiate malignant lesions from benign ones.

CASE REPORTS

Case Report 1:

A brown, male, 13 year-old student sought medical care with a complaint of nail spots. He presented with asymptomatic lesions on the 1^st right digit for six years and on the 3rd right digit for eight years. The dermatologic examination revealed a black melanonychia, measuring approximately 9 mm wide on the 1^st right digit (Figura 1A) and a brown melanonychia, measuring approximately 1 mm wide also on the 3rd digit (Figura 1B). Dermatoscopy was performed only on the nail plate of lesions. The side of the 1^st right digit presented light and dark brown color pigmentation, distributed in a linear and parallel fashion throughout the nail from the cuticle to the free border. On the medial portion of the same nail we observed a change in pattern, replaced by a totally amorphous and irregular area, affecting the proximal nail fold – the micro-Huntchinson sign, only seen on dermatoscopy⁵ (Figura 1C). As these characteristics are suggestive of malignancy, the main diagnostic hypothesis was melanoma and, therefore a biopsy of the 1^st digit was indicated. A brown color was observed on the 3rd right digit with parallel longitudinal lines, regular in space, width and color (Figura 1D). Given such dermatoscopy characteristics are suggestive of a benign lesion the main diagnostic hypothesis was melanocytic nevus and watchful waiting management. Histopathology of the nail matrix of the 1^st right digit showed pleomorphic melanocytic cells that proliferated in the lower layers of the epithelium forming irregular asymmetric groups, findings compatible with in situ melanoma⁶ (Figura 2). Management was the exeresis of the lesion with 0.5cm margins on the side and proximal folds in depth to bone tissue and with second intention healing.⁷ Histopathology analysis confirmed the diagnosis, and showed that most of the lesion had been removed by the previous biopsy (Figura 3).

Case Report 2:

White, female, 63 year old housewife sought medical care with a complaint of a nail spot. For over a year she had an asymptomatic lesion on her 5th left digit. The dermatologic examination showed brown melanonychia, measuring approximately 6.5 to 7 mm wide, on the 5th left digit (Figura 4A). Both the direct exam and culture for fungi were negative. Dermatoscopy revealed brown parallel homogeneous longitudinal lines; regular in space, width and color on the left 5th digit nail (Figura 4B). Main diagnostic hypotheses were melanocytic nevus and subungueal lentigo. Although the characteristics of the lesion on dermatoscopy suggested a benign nature, some clinical-epidemiological characteristics pointed toward malignancy such as width of the lesion, a sole digit affected, patient age and phototype. For this reason management was nail exeresis and posterior biopsy of the nail matrix for histopathology. After nail exeresis, the pigmented lesion that took over approximately µof the nail, now represented a small extension of the nail bed (Figura 4C). Histopathology showed lengthening of epidermal ridges and increase in the amount of melanin on the basal layer, compatible with subungueal lentigo⁶ (Figura 5). We chose clinical follow-up as therapeutic management.

DISCUSSION

Melanonychia may have several etiologies, from physiologic lesions to malignant neoplasms, therefore the importance of early etiological diagnosis.

Melanonychias may be total or longitudinal. Longitudinal melanonychias are also called striata, and are more frequent in African and Asian, than in White individuals; the incidence is higher in the over 50 age group, and the 1^st and 2nd fingers are most commonly affected.^1,3,4 It is important to point out that the epidemiology is similar to that of acral melanoma, which is the most frequent melanoma subtype in African and Asian individuals, mainly affects patients between 50 and 70 years, and most commonly affects the 1^st digit and the 1^st toe without gender preference.^1,3,4

In order to make the etiological differentiation of the lesions easier, the nail ABCDEF rule and dermatoscopy of the nail plate are increasingly used, in that nail bed dermatoscopy is a promising test.^{3,5, 8,9,10,11,12}

The ABCDEF rule is useful for differentiating benign from malign melanonychia. Suggestive characteristics of malignancy are:⁸

A. Age: 50 to 70 years; African and Asian origin.

B. Band: over 3 mm; Brown (brown), Black (black).

C. Change: nail band; nail morphology.

D. Digit involved: thumb, halux, single.

E. Extension: Hutchinson's sign.

F. Family and personal history: dysplastic nevus syndrome or previous melanoma.

Another important resource is nail plate dermatoscopy, in which patterns for melanocytic lesions are described (Figura 6).

Currently, dermatoscopy of the nail bed and of the distal nail fold have also been used.^11,12,13

Whenever dermatoscopy is not accessible, criteria to help perform the biopsy are:^1,8

• A single nail affected.

• Brown or Black band > 3 mm.

• periungueal pigment effusion – Hutchinson's Sign.

Our opinion is that exeresis of the entire nail plate during biopsy enables to determine the actual size of the lesion. New studies are still necessary, but we have observed that after the removal of the nail plate the melanocytic lesion of the case patient became smaller than the pigmented band observed on the nail plate. The matrix lesion works as a pigment "fountain", distributing melanin throughout the nail plate. Once the plate is removed, it is easier to choose the most appropriate site for biopsy and consequently attainment of the best histopathology assessment.

Despite the major help of the ABCDEF rule, as is the case of lesion dermatoscopy, histopathology still is indispensable in cases of uncertainty.¹⁴ However, histology of the nail system has some peculiarities that should be acknowledged by the pathologist in order to enable correct interpretation. Melanocytes of the nail matrix are different from local melanocytes of any other skin site as they are: (1) fewer in number; (2) generally quiescent; (3) reside on the two to four inferior layers of germinative cells, instead of on the basal cell layer.¹ For this reason, histopathology findings in melanocytic nail lesions are in general more subtle. In case 2, for example, diagnosed as lentigo, the degree of melanocytic hyperplasia is very small, but it is associated with a lentiginous hyperplasia of the epidermis (acanthosis with regular lengthening of cones) which is not observed in racial melanonychia. It should also be pointed out that the literature related to the distribution of melanocytes in the normal nail matrix is scarce.¹⁵

The present report is an example of two clinical cases of melanonychia in patients of different age groups and race. Case 1 highlights the occurrence, albeit rare, of a melanoma in a young patient. As melanoma in situ is an intraepithelial neoplasm, in which the possibility of metastasizing does not exist in theory, we chose not to amputate the phalanx/digit in the patient, having preferred a conservative surgery, and consequently more functional management. This patient had a second lesion that, according to the dermatoscopy was considered benign. The ABCDEF rule was useful, but not enough to differentiate between benign and malignant lesions. Dermatoscopy of both the nail plate and bed is extremely valuable to differentiate melanocytic from non melanocytic lesions; and the pattern found in a melanocytic lesion may indicate a benign or malignant lesion. The exeresis of the nail plate – performed on case 2 patient – enabled the observation of the nail matrix and bed, and the possibility of better assessing the lesion to be studied, allowing a more accurate indication of the site to be submitted to biopsy.

REFERENCES

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• 11. Hirata SH, Yamada S, Almeida FA, Yamashita JT, Enokihara MY, Paschoal FM, et al. Dermatoscopy of the nail bed and matrix to assess melanonychia striata. J Am Acad Dermatol. 2005;53:884-6.
• 12. Hirata SH, Yamada S, Almeida FA, Enokihara MY, Rosa, IP, Enokihara MM, et al. Dermatoscopic examination of the nail bed and matrix. Int J Dermatol. 2006;45:28-30.
• 13. Braun RP, Baran R, Saurat JH, Thomas L. Surgical pearl: dermoscopy of the free edge of the nail to determine the level of nail plate pigmentation and the location of its probable origin in the proximal or distal nail matrix. J Am Acad Dermatol. 2006;55:512-3.
• 14. Husain S, Scher RK, Silvers DN, Ackerman AB. Melanotic macule of nail unit and its clinicopathologic spectrum. J Am Acad Dermatol. 2006;54:664-7.
• 15. Perrin C, Michiels JF, Pisani A, Ortonne JP. Anatomic distribution of melanocytes in normal nail unit: an immunohistochemical investigation. Am J Dermatophatol. 1997;19:462-7.

*

Trabalho realizado no Instituto de Dermatologia Professor Rubem David Azulay da Santa Casa da Misericórdia do Rio de Janeiro – Rio de Janeiro (RJ), Brasil.

Publication Dates

• Publication in this collection
  03 June 2009
• Date of issue
  Apr 2009

History

• Accepted
  29 Feb 2008
• Received
  16 Mar 2007