10.5826/dpc.0901a10
The term melanonychia describes a black-brown-gray pigmentation of the nail plate that, in most cases, appears as a longitudinal band. Melanonychia can be observed at any age, affecting one digit or several digits, in both fingernails and toenails. Its causes can be difficult to differentiate clinically and depend on the number of bands and on their color, edge, and width. For this reason, especially in adults and when the pigmentation is localized in one single digit, biopsy and histopathological examination still represent the gold standard for a definitive diagnosis. Dermoscopy should be used routinely in the evaluation of a pigmented nail, as it provides important information for the management of melanonychia and can help avoid unnecessary nail biopsies. In cases of melanonychia it is important to establish whether the pigment is melanin or not and to determine whether the pigmentation of melanin is due to activation or proliferation and whether it is benign or malignant.
application/xml
2160-9381
556
en
Bianca Maria Piraccini
Copyright (c) 2019 Michela Starace, Aurora Alessandrini, Nicolò Brandi, Bianca Maria Piraccini
Dermatology Practical & Conceptual
nail
Use of Nail Dermoscopy in the Management of Melanonychia
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Review
2019-01-31
2018-07-12
2019-01-31
2021-11-16
38-43
Dermatol Pract Concept
The term melanonychia describes a black-brown-gray pigmentation of the nail plate that, in most cases, appears as a longitudinal band. Melanonychia can be observed at any age, affecting one digit or several digits, in both fingernails and toenails. Its causes can be difficult to differentiate clinically and depend on the number of bands and on their color, edge, and width. For this reason, especially in adults and when the pigmentation is localized in one single digit, biopsy and histopathological examination still represent the gold standard for a definitive diagnosis. Dermoscopy should be used routinely in the evaluation of a pigmented nail, as it provides important information for the management of melanonychia and can help avoid unnecessary nail biopsies. In cases of melanonychia it is important to establish whether the pigment is melanin or not and to determine whether the pigmentation of melanin is due to activation or proliferation and whether it is benign or malignant.
Bianca Maria Piraccini
2019/01/31
10.5826/dpc.0901a10
38
Department of Experimental, Diagnostic and Specialty Medicine-Division of
 Dermatology, University of Bologna, Bologna, Italy
2160-9381
nail
en
43
Use of Nail Dermoscopy in the Management of Melanonychia
https://dpcj.org/index.php/dpc/article/download/556/345
                    Dermatology Practical & Conceptual


              Use of Nail Dermoscopy in the Management
                       of Melanonychia: Review
               Michela Starace1, Aurora Alessandrini1, Nicolò Brandi1, Bianca Maria Piraccini1


1 Department of Experimental, Diagnostic and Specialty Medicine-Division of_Dermatology, University of Bologna, Bologna, Italy



Key words: pigmentation, melanonychia, dermoscopy, nail
Citation: Starace M, Alessandrini A, Brandi N, Piraccini BM. Review of the use of nail dermoscopy in the management of melanonychia:
Review. Dermatol Pract Concept. 2019;9(1):38-43. DOI: https://doi.org/10.5826/dpc.0901a10
Published: January 31, 2019
Copyright: ©2019 Starace et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: None.
Competing interests: The authors have no conflicts of interest to disclose.
Authorship: All authors have contributed significantly to this publication.
Corresponding author: Michela Starace MD, PhD, Department of Experimental, Diagnostic and Specialty Medicine-Division of
Dermatology, University of Bologna, Bologna, Italy, Via Massarenti, 1, 40138 Bologna, Italy. Email: michela.starace2@unibo.it




  ABSTRACT              The term melanonychia describes a black-brown-gray pigmentation of the nail plate that, in most
                        cases, appears as a longitudinal band. Melanonychia can be observed at any age, affecting one digit
                        or several digits, in both fingernails and toenails. Its causes can be difficult to differentiate clinically
                        and depend on the number of bands and on their color, edge, and width. For this reason, especially in
                        adults and when the pigmentation is localized in one single digit, biopsy and histopathological exami-
                        nation still represent the gold standard for a definitive diagnosis. Dermoscopy should be used routinely
                        in the evaluation of a pigmented nail, as it provides important information for the management of
                        melanonychia and can help avoid unnecessary nail biopsies. In cases of melanonychia it is important to
                        establish whether the pigment is melanin or not and to determine whether the pigmentation of melanin
                        is due to activation or proliferation and whether it is benign or malignant.



Introduction                                                             melanonychia). Melanonychia can be observed at any age,
                                                                         affecting one digit or several digits, in both fingernails and
The term melanonychia describes a black-brown-gray                       toenails.
pigmentation of the nail plate. Although nail matrix mela-                    The causes of longitudinal melanonychia can be difficult
nocytes are normally quiescent, these cells can eventually               to differentiate clinically and, first of all, depend on the
become activated with or without proliferation, thus induc-              number of the bands and on their color, edge, and width.
ing the pigmentation of the nail plate. Melanonychia can                 Biopsy and histopathological examination is recommended
present itself in many different ways, but most frequently it            when a longitudinal melanonychia occurs in an adult and it
appears as a longitudinal band (longitudinal melanonychia)               is localized in one single digit, even more so in the absence of
that starts from the proximal margin of the nail and extends             local or systemic causes that may explain its onset. The real
to the distal margin, following the growth of the nail.                  problem of how to distinguish whether the lesion is benign
Less commonly, the pigment can be transverse (transverse                 or malignant remains, as an early diagnosis of melanoma can
melanonychia) [1] or even involve all of the nail plate (total           be crucial for the prognosis.



38                                                                                          Review | Dermatol Pract Concept 2019;9(1):10
   With this in mind, dermoscopy
                                                A                                         B
should be used routinely in the evalua-
tion of a pigmented nail, as it provides
important information for the manage-
ment of melanonychia and can help
to avoid unnecessary nail biopsies. In
case of melanonychia, it is important to
follow 3 steps: (1) to establish whether
the pigment is melanin or not, (2) to
determine whether the pigmentation of
melanin is due to activation or prolif-
eration, and (3) if it is a proliferation,     Figure 1. Dermoscopy of a brown-black nail pigmentation due to subungual hematoma.
to determine whether it is benign or           Red-purple globule pattern within the nail plate with homogeneous color of the pigmenta-
malignant [2].                                 tion peripherally fading (A). The pigmentation disappears with nail clipping (B). [Copyright:
                                               ©2019 Starace et al.]


Discussion
When performing dermoscopy on nail
pigmentation, it is important to observe
all the visible part of the nail unit where
it is possible to put the dermatoscope.
Moreover, it is fundamental to remem-
ber that the use of gel is recommended
for the examination of any pigmented
lesions because it increases the visibility
through the nail plate, even if it is more
difficult with the gel because of the ten-
dency to slide off the plate.                  Figure 2. Melanonychia due to onychomy-         Figure 3. Dermoscopy of green nails due to
   First of all, dermoscopy permits dif-       cosis caused by Trichophyton rubrum vari-       Pseudomonas aeruginosa colonization of
                                               ant melanoid. [Copyright: ©2019 Starace         the nail. The convexity of the onycholytic
ferentiating melanocytic from nonme-
                                               et al.]                                         border is linear. [Copyright: ©2019 Starace
lanocytic pigmentation, particularly the
                                                                                               et al.]
quite common brown-black nail discol-
orations due to subungual hematoma or
fungal infection [3]. In fact, melanocytic     tion, which peripherally fades and lacks        In green nails, the pigmentation is due to
pigmentation is generally brown-black,         the longitudinal lines of true melano-          bacterial colonization by Pseudomonas
within the nail plate and with a lon-          nychia (Figure 1). Fungal melanonychia          aeruginosa and is characterized by a
gitudinal aspect, whereas exogenous            is a rare variant of onychomycosis              bright green color that fades to yellow,
pigmentation typically includes the            caused by Trichophyton rubrum vari-             laying under the nail plate [5] (Figure 3).
spectrum of color of the substance that        ant melanoid, which can present itself              If the pigmentation is due to melanin
adheres to the nail plate and does not         with a longitudinal band on the nail            produced by nail matrix, the second step
always have a longitudinal appearance          plate, thus further complicating differ-        of melanonychia management is to iden-
located near the nail folds or in the cen-     ential diagnosis. Dermoscopy of fungal          tify whether the pigmentation is due to
ter of the nail plate. The most common         melanonychia reveals a usually brown            an activation or proliferation. The num-
causes of nonmelanocytic pigmentation          band of melanonychia, with thick sub-           ber of digits involved is an important
include subungual hematoma, fungal             ungual hyperkeratosis and yellow and            diagnostic clue: if more than one digit is
melanonychia, and green nails. Sub-            brown scales, wider at the distal ends          affected, it is likely to be a melanocytic
ungual hematoma is one of the most             and focalizing on reddish hue that may          activation. The dermoscopic pattern
frequent causes of brown-black nail pig-       be related to traumatic hemorrhages             that suggests a melanocytic activation is
mentation, and blood can be recognized         from subungual hyperkeratosis; more-            a gray background of the band with thin
by the presence of the red-purple-brown        over, there are no visible inclusions of        grayish regular and parallel lines (Fig-
globule pattern within the nail plate and      melanin, supporting a nonmelanocytic            ure 4); moreover, hyperpigmentation
the homogeneous color of the pigmenta-         origin of the pigmentation [4] (Figure 2).      of the nail can also be associated with



Review | Dermatol Pract Concept 2019;9(1):10                                                                                            39
 A                                                            B                                        C




Figure 4. Clinical picture of melanocytic activation affecting all fingernails during combined chemotherapy (A); onychoscopy reveals gray
background of the bands with thin grayish regular and parallel lines, associated with Muehrcke lines, which appear as white parallel trans-
verse bands (B, C). [Copyright: ©2019 Starace et al.]



a hyperpigmentation of the periungual          allow us to differentiate melanonychia
skin [6]. When multiple nails present          due to benign melanocytic proliferation,
longitudinal melanonychia, it is impor-        ie, nail matrix lentigo or nevus, from
tant to consider a normal ethnic/racial        melanonychia due to malignant mela-
variant, particularly in darker skin pho-      nocytic proliferation [7].
totypes; the use of drugs; mechanical              The first cutoff in cases of longitu-
factors such as frictional melanonychia        dinal melanonychia due to prolifera-
and onychotillomania; pregnancy; or an         tion is the age of the patient since nail
inflammatory disease or the manifesta-         melanoma is rare in children; only 20
tion of one of the multiple signs of a syn-    cases are described in the literature,
drome, such as Peutz-Jeghers syndrome          frequently in darker skin phototypes
and Laugier-Hunziker syndrome [5].             [6-10]. Dermoscopic patterns that sug-
Frictional melanonychia is a very com-         gest melanoma in children are rapid
mon form of melanocytic activation and         evolution of brown background with               Figure 5. Nail dermoscopy of frictional mel-
                                                                                                anonychia of the fifth toenail. Nail pigmen-
is typically localized only on the fifth       longitudinal brown to black lines with
                                                                                                tation is gray-brown with a brown back-
and/or fourth toenails, due to the fre-        irregular degree of color pigmentation,
                                                                                                ground with parallel thin lines. [Copyright:
quently chronic friction of these digits       spacing or varying thickness and ending          ©2019 Starace et al.]
with the shoes. The band is usually gray-      abruptly or having a parallel distribu-
black and its background is brown with         tion. However, these features can also be
parallel thin lines (Figure 5); in some        seen in nail matrix nevi in children and         lar and parallel lines with regular spac-
cases, the friction of the toenails could      thus their specificity is low. For this rea-     ing and thickness. A new dermoscopic
induce trauma in the capillaries, thus         son, dermoscopy could have less value            sign that can indicate a regression of a
leading to the appearance of red spots         in childhood melanonychia [11].                  nevus and not represent a warning sign
or splinter hemorrhages that reinforce             Nonetheless nail matrix nevi may be          of a melanoma, especially in children, is
the traumatic etiology of the pigmented        present at birth; they can also occur with       the presence of black dots along mela-
band. In a similar way, in onychotillo-        age. Nail matrix nevi affect fingernails         nocytic lines [12]. These dots are black,
mania the mechanical trauma of biting          more frequently than toenails, most              with a regular size and shape (less than
of the proximal nail folds induces an          often the thumb. Usually, the nail has           0.1 mm), and are distributed along the
activation of the melanocytes. In these        one or more longitudinal heavily pig-            pigmented lines; sometimes they form a
cases, however, it is frequent to observe      mented bands whose size can vary from            shallow pit at the periphery while other
more digits involved and signs of chew-        a few millimeters to the whole nail and          times it is possible to find them within
ing such as crusts or wounds on the            whose color may not be homogeneous               the pigmented lines, often interrupting
most affected digits.                          and more or less dark [3]. Dermoscopic           them. The authors have explained the
     Dermoscopy of melanocytic nail            patterns that suggest a nail matrix nevus        presence of these dots as an accumula-
pigmentation is difficult to interpret, as     are the presence of a brown background           tion of melanin derived from a clus-
there are still not uniform criteria that      with longitudinal brown to black regu-           ter of nevus cells that migrate upward



40                                                                                            Review | Dermatol Pract Concept 2019;9(1):10
                                                    A                                    B




Figure 6. Dermoscopy of a nail matrix nevus
in a 5-year-old child. Brown background with
longitudinal brown to black irregular and not
                                                   Figure 7. Clinical picture of nail melanoma of the II digit of right hand (A); a brown-black
parallel lines with irregular spacing and thick-
                                                   band of melanonychia characterized by irregular lines in their thickness, spacing, color, and
ness, with the presence of black dots along
                                                   parallelism at dermoscopy (B). [Copyright: ©2019 Starace et al.]
melanocytic lines. The pseudo-Hutchinson
sign is also evident in the proximal nail fold.
[Copyright: ©2019 Starace et al.]


                                                   the years, first for the use of the ABCDs       range from 1 mm to spanning the entire
                                                   rule for nail pigmentation [15] and sec-        nail plate, the corresponding nail plate
from the dermo-epidermal junction. In              ond for the introduction of nail dermos-        can show some changes or be completely
most young patients, the disappearance             copy [16] and its criteria for benign and       normal, and, finally, brown-black peri-
of the dots will occur over time and               malignant lesions [17]. In fact, even if        ungual pigmentation (Hutchinson sign)
will accompany the fading of melano-               the ABDEF rule is a useful clinical tool        may or may not be present.
nychia. Dark bands are associated with             to suspect a melanoma, nail dermoscopy              The dermoscopic features of benign
pseudo-Hutchinson sign, because the                offers further help and permits seeing          melanocytic proliferation are character-
dark nail plate pigmentation is visible            with high magnification the details of          ized by gray or brown homogeneous
through the transparent nail fold (illu-           the pigmentation aspects not visible to         color of the background and brown
sory phenomenon); the pigmentation                 the naked eye, enabling the visualization       bands with multiple thin brown lines;
may be homogeneously distributed or                of different signs of melanoma. How-            these lines are usually regular and paral-
darker bands may appear over diffuse               ever, it is important to remember that          lel to each other, with regular spacing and
pale pigmentation (Figure 6). Periun-              dermoscopy is not always reliable in the        thickness and similar shades of brown
gual pigmentation is typical in congeni-           evaluation and management of the pig-           throughout the whole lesion, as in nevi.
tal nevi and may involve both the nail             mented nail [18], since there are some          On the contrary, dermoscopic features
proximal fold and the hyponychium,                 conditions for which dermoscopy is not          suggestive of nail melanoma include a
thus alarming the clinician. In children,          performable, such as thickened nails,           brown to black background of the band
it is not uncommon to notice a gradual             blurred borders of the lesions, and a nail      with longitudinal lines irregular in their
darkening and enlargement of the band              plate that is totally black [5,18]. Because     thickness, spacing, color, or parallelism
that may have a proximal part broader              of its rarity, there are only a few stud-       [17] (Figure 7). However, this rule is not
than the distal (triangular shape); thin-          ies focused on melanoma dermoscopic             always reliable, as it is possible to find
ning and fissuring of the pigmented nail           features; therefore, dermoscopy should          lines that are irregular in width or color
plate may also occur. It is also quite             still be assisted by the clinical features      also in benign lesions [5,18].
common to observe a gradual fading of              and the history of the nail pigmentation.           A recent study identified 3 impor-
the band with age [13]. This “regressing                When only one digit is involved by         tant dermoscopic features that could
nevoid nail melanoma in childhood” is              melanonychia, a proliferative process           help to distinguish whether the band
unique to children and not indicative              has to be considered and a diagnosis of         is benign or malignant. In particular, a
of regression of the nevus but may just            melanoma suspected. The clinical fea-           band involving more than two-thirds of
indicate decreased melanocytic activity            tures of the band can be very different:        the nail plate, a color gray to black, and
from nevus cells [14].                             the color can be more or less pronounced        the presence of nail dystrophy increase
    The diagnostic accuracy of longitu-            and homogeneous, the borders can be             3 times the risk of detecting a nail mela-
dinal melanonychia has improved over               well defined or less sharp, the width can       noma [19].



Review | Dermatol Pract Concept 2019;9(1):10                                                                                                41
 A                           B                                                   D




                             C
                                                                                 E




Figure 8. Amelanotic melanoma of the toenail. At clinical examination the absence of the nail plate with ulceration is evident (A); dermos-
copy magnifies a nail bed nodule with irregular vascular pattern with milky red veil and Hutchinson sign at hyponychium (B-E). [Copyright:
©2019 Starace et al.]




     Dermoscopy of the free edge of the distal nail plate can          prominently dotted vessels [20]. Distinguishing this tumor
also be very helpful in distinguishing whether the pigment             from pyogenic granuloma could be difficult sometimes.
is produced by proximal or distal nail matrix. In fact, if the             In summary, dermoscopy is useful for the diagnosis of
pigment is in the dorsal part of the free edge its origin comes        melanoma in adults especially in 2 cases: when there is the
from the proximal nail matrix, while if the pigment is in              micro-Hutchinson sign, ie, when melanoma is present as an
the ventral part of the free edge its origin is the distal nail        ulcerated nodule of the nail bed, and when melanoma is pres-
matrix [5]. Moreover, dermoscopic features of the nail plate           ent as a band of longitudinal melanonychia, not associated
and periungual tissues also offer interesting information for          with periungual pigmentation and/or nail plate changes. A
the selection of cases in which pathological examination is            useful algorithm may help us to understand what is the best
indicated, permitting the evaluation of Hutchinson sign, one           management in case of suspected nail apparatus melanoma
of the most important signs of malignancy. Dermoscopically,            and possibly allow an earlier diagnosis with detection of in
this sign appears as a brown-black periungual pigmentation,            situ nail melanoma [21].
characterized by polychromia and asymmetry. However, the                   False-negative and false-positive dermoscopic results are
most important role of nail dermoscopy is the ability to detect        not rare, especially in cases of benign lesions with irregular
the micro-Hutchinson sign, a periungual pigmentation visible           lines. Nevertheless, a delayed diagnosis of melanoma remains
only with a dermatoscope and not with the naked eye, which             common and a poor prognosis is often attributable to long-
represents an initial sign of radial growth into adjacent tissue.      standing disease. The misdiagnosis rate has been found to be
Moreover, the micro-Hutchinson sign could be present also              higher than 20% [22].
in amelanotic melanoma, a malignant lesion characterized                   Intraoperative dermoscopy enables visualization of the
by the lack of melanin pigment. The clinical features of this          origin of the pigmentation, revealing aspects not observed
type of melanoma are the absence of the nail plate and a nail          when the nail plate is interposed between the pigmented
dystrophy due to nail bed hyperkeratosis or ulceration; other          lesion and the dermatoscope [23]. This type of dermoscopy
dermoscopic patterns typical of amelanotic melanoma are                is more reliable and accurate than plate dermoscopy and has
eroded nail bed nodule, vascular pattern characterized by a            high sensitivity and specificity in differentiating pigmented
red discoloration with a milky-red veil and variable aspect of         nail lesions, albeit is a part of an invasive procedure and
vessels, with some appearing as dots and others as irregular           cannot be performed in all cases of melanonychia. With the
lines. The color of amelanotic melanoma is white in the center         intraoperative method, 4 dermoscopic features have been
of the lesion and red in the periphery (Figure 8) and can also         recognized: regular gray pattern, typical of hypermelanosis;
correlate with the duration of the lesion. In older lesions the        regular brown pattern, typical of benign melanocytic hyper-
predominant color is dark red, probably due to the presence            plasia; regular brown pattern with globules or blotches,
of crusts and vascular disarrangement, with irregular vessels          typical of melanocytic nevi; and irregular pattern, typical of
assuming a mix of hairpin, linear, or dotty aspect; on the other       melanoma. The use of intraoperative procedure may facilitate
hand, younger lesions have a lighter red color and present             selecting the best site to perform biopsy [24].



42                                                                                          Review | Dermatol Pract Concept 2019;9(1):10
    There are no evidence-based studies that determine the                    9. Uchiyama M, Minemura K. Two cases of malignant melanoma in
ideal frequency of dermoscopic follow-up in patients with                        young persons. Nippon Hifuka Gakkai Zasshi. 1979;89:668.
longitudinal melanonychia nor any that make precise dermo-                   10. Iorizzo M, Tosti A, Di Chiacchio N, et al. Nail melanoma in
                                                                                 children: differential diagnosis and management. Dermatol Surg.
scopic criteria to decide when the pigmented lesions require
                                                                                 2008;34(7):974-978.
biopsy [3]. One suggestion is to monitor the patient every
                                                                             11. Tosti A, Piraccini BM, Cagalli A, Haneke E. In situ melanoma
6 months with dermoscopy in cases of benign melanocytic                          of the nail unit in children: report of two cases in fair-skinned
lesions and to have a strict follow-up every 3 months in cases                   Caucasian children. Pediatr Dermatol. 2012;29(1):79-83.
of irregular pigmentation without other signs of malignancy                  12. Murata Y, Kumano K. Dots and lines: a dermoscopic sign of
[25]. Nevertheless, the gold standard for a definitive diagnosis                 regression of longitudinal melanonychia in children. Cutis.
of nail pigmentation still remains histopathology [26,27].                       2012;90:293-296.
                                                                             13. Tosti A, Baran R, Morelli R, et al. Progressive fading of a longi-
                                                                                 tudinal melanonychia due to a nail matrix melanocytic nevus in
Conclusions                                                                      a child. Arch Dermatol. 1994;130(8):1076-1077.
                                                                             14. Kikuchi I, Inoue S, Sakaguchi E, Ono T. Regressing nevoid nail
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                                                                                 ABC rule for clinical detection of subungual melanoma. J Am
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                                                                                 Acad Dermatol. 2000;42(2):269-274.
    The causes of melanonychia vary from subungual hema-
                                                                             16. Ronger S, Touzet S, Ligeron C, et al. Dermoscopic examination
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                                                                                 of nail pigmentation. Arch Dermatol. 2002;138(10):1327-1333.
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                                                                                 melanonychia nail plate dermoscopy. An Bras Dermatol.
the pigment. It is an important technique for the evaluation
                                                                                 2013;88(2):309-313.
of melanocytic pigmentation; however, it has to be added to
                                                                             19. Benati E, Riberio S, Longo C, et al. Clinical and dermoscopic
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                                                                                 2017;31(4):732-736.
                                                                             20. Phan A, Dalle S, Touzet S, Ronger-Savlé S. Balme B, Thomas
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