10.5826/dpc.1304a204
Melanonychia striata longitudinalis might involve one or more fingers and/or toes and might result from several different causes, including benign and malignant tumors, trauma, infections, and acti-vation of melanocytes that might be reactive or related to the pigmentary trait,drugs and some rare syndromes.This broad differential diagnosis renders the clinical assessment of melanonychia striata particularly challenging. Nail matrix melanoma is relatively rare, occurs almost always in adults in-volves more frequently the first toe or thumb.The most common nail unit cancer,squamous cell carcinoma / Bowen disease (SCC) of the nail matrix is seldom pigmented. Histopathologic examina-tion remains the gold standard for melanoma and SCC diagnosis,but excisional or partial biopsies from the nail matrix require training and is not routinely performed by the majority of clinicians.Furthermore, the histopathologic evaluation of melanocytic lesions of the nail matrix is particularly challenging, since early melanoma has only bland histopathologic alterations. Dermatoscopy of the nail plate and its free edge significantly improves the clinical diagnosis, since specific patterns have been associated to each one of the causes of melanonychia. Based on knowledge generated and pub-lished in the last decades, we propose herein a stepwise diagnostic approach for melanonychia striata longitudinalis: 1) Hemorrhage first 2) Age matters 3) Number of nails matters 4) Free edge matters 5) Brown or gray? 6) Size matters 7) Regular or irregular and, finally,“follow back”.
text/xml
2160-9381
3191
en
Luc Thomas
https://creativecommons.org/licenses/by-nc/4.0
Dermatology Practical & Conceptual
dermatoscopy
Seven Plus One Steps to Assess Pigmented Nail Bands (Melanonychia Striata Longitudinalis)
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Opinion
2023-10-31
2023-01-28
2023-10-31
2024-01-15
e2023204
Dermatol Pract Concept
Melanonychia striata longitudinalis might involve one or more fingers and/or toes and might result from several different causes, including benign and malignant tumors, trauma, infections, and acti-vation of melanocytes that might be reactive or related to the pigmentary trait,drugs and some rare syndromes.This broad differential diagnosis renders the clinical assessment of melanonychia striata particularly challenging. Nail matrix melanoma is relatively rare, occurs almost always in adults in-volves more frequently the first toe or thumb.The most common nail unit cancer,squamous cell carcinoma / Bowen disease (SCC) of the nail matrix is seldom pigmented. Histopathologic examina-tion remains the gold standard for melanoma and SCC diagnosis,but excisional or partial biopsies from the nail matrix require training and is not routinely performed by the majority of clinicians.Furthermore, the histopathologic evaluation of melanocytic lesions of the nail matrix is particularly challenging, since early melanoma has only bland histopathologic alterations. Dermatoscopy of the nail plate and its free edge significantly improves the clinical diagnosis, since specific patterns have been associated to each one of the causes of melanonychia. Based on knowledge generated and pub-lished in the last decades, we propose herein a stepwise diagnostic approach for melanonychia striata longitudinalis: 1) Hemorrhage first 2) Age matters 3) Number of nails matters 4) Free edge matters 5) Brown or gray? 6) Size matters 7) Regular or irregular and, finally,“follow back”.
Luc Thomas
2023/10/31
10.5826/dpc.1304a204
e2023204
Service de Dermatologie, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, Lyon, France; Université Claude-Bernard-Lyon Lyon, Lyon, France and Lyons cancer research center UMR INSERM U1052 - CNRS5286 - UCBL1 Lyon France
2160-9381
dermatoscopy
en
e2023204
Orentreich N, Markofsky J, Vogelman JH. The effect of aging on the rate of linear nail growth. J Invest Dermatol. 1979 Jul;73(1):126-30. doi: 10.1111/1523-1747.ep12532799. PMID: 448171.
Seven Plus One Steps to Assess Pigmented Nail Bands (Melanonychia Striata Longitudinalis)
https://dpcj.org/index.php/dpc/article/download/3191/2398
      Seven Plus One Steps to Assess Pigmented Nail
       Bands (Melanonychia Striata Longitudinalis)
                 Aimilios Lallas,1 Katarzyna Korecka,2 Zoe Apalla,3 Dimitrios Sgouros,4
                      Konstantinos Liopyris,5 Giuseppe Argenziano,6 Luc Thomas7


1 First Dermatology Department, School of Medicine, Faculty of Health Sciences, Aristotle University, Thessaloniki, Greece
2 Department of Dermatology, Heliodor Swiecicki Clinical Hospital, University of Medical Sciences, Poznan, Poland
3 Second Dermatology Department, School of Medicine, Faculty of Health Sciences, Aristotle University, Thessaloniki, Greece
4 Second Department of Dermatology and Venereology, ATTIKON General University Hospital, Medical School, National and Kapodistrian
  University, Athens, Greece
5 Andreas Sygros Hospital for Cutaneous and Venereal Diseases, Athens, Greece
6 Dermatology Unit, Department of Mentals and Physical Health and Preventive medicine, University of Campania Luigi Vanvitelli Naples,
  Napoli, Italy
7 Service de Dermatologie, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, Lyon, France; Université Claude-Bernard-Lyon Lyon, Lyon,
  France and Lyons cancer research center UMR INSERM U1052 - CNRS5286 - UCBL1 Lyon France



Citation: Lallas A, Korecka K, Apalla Z, et al. Seven Plus One Steps To Assess Pigmented Nail Bands (Melanonychia Striata Longitudinalis).
Dermatol Pract Concept. 2023;13(4):e2023204. DOI: https://doi.org/10.5826/dpc.1304a204
Accepted: February 21, 2023; Published: October 2023
Copyright: ©2023 Lallas et al. This is an open-access article distributed under the terms of the Creative Commons
Attribution-NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted
noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited.
Funding: None.
Competing Interests: None.
Authorship: All authors have contributed significantly to this publication.
Corresponding Author: Aimilios Lallas, First Department of Dermatology, School of Medicine, Aristotle University, Thessaloniki, Greece.
Tel.: +302313308879 E-mail: alallas@auth.gr




  ABSTRACT             Melanonychia striata longitudinalis might involve one or more fingers and/or toes and might result
                       from several different causes, including benign and malignant tumors, trauma, infections, and acti-
                       vation of melanocytes that might be reactive or related to the pigmentary trait, drugs and some rare
                       syndromes. This broad differential diagnosis renders the clinical assessment of melanonychia striata
                       particularly challenging. Nail matrix melanoma is relatively rare, occurs almost always in adults in-
                       volves more frequently the first toe or thumb. The most common nail unit cancer, squamous cell
                       carcinoma / Bowen disease (SCC) of the nail matrix is seldom pigmented. Histopathologic examina-
                       tion remains the gold standard for melanoma and SCC diagnosis, but excisional or partial biopsies
                       from the nail matrix require training and is not routinely performed by the majority of clinicians.
                       Furthermore, the histopathologic evaluation of melanocytic lesions of the nail matrix is particularly
                       challenging, since early melanoma has only bland histopathologic alterations. Dermatoscopy of the
                       nail plate and its free edge significantly improves the clinical diagnosis, since specific patterns have
                       been associated to each one of the causes of melanonychia. Based on knowledge generated and pub-
                       lished in the last decades, we propose herein a stepwise diagnostic approach for melanonychia striata
                       longitudinalis: 1) Hemorrhage first 2) Age matters 3) Number of nails matters 4) Free edge matters
                       5) Brown or gray? 6) Size matters 7) Regular or irregular and, finally, “follow back”.


Opinion | Dermatol Pract Concept. 2023;13(4):e2023204                                                                                     1
Introduction                                                      or discomfort for the patients. Therefore, there is no signifi-
                                                                  cant barrier for clinicians to excise equivocal lesions located
Melanonychia striata longitudinalis is a term of Greek-Latin      on the trunk or extremities or biopsy doubtful lesions on
origin still used to describe the presence of a proximal          anatomically sensitive areas such as the face.
to-distal linear pigmentation of the nail plate [1-3]. A pig-        In contrast, an excisional or partial biopsy form the nail
mented nail band might have variable width, might involve         matrix is a much more demanding procedure that requires
one or more fingers and/or toes and might result from sev-        training and is not routinely performed by the majority of
eral different causes [1,3,4]. The list of disorders that may     clinicians [11]. It is considered as a complex, painful proce-
cause nail pigmentation includes benign and malignant tu-         dure with an associated risk of a permanent damage to the
mors, trauma, infections, and activation of melanocytes that      nail plate, although the latter is not necessarily true. Further-
might be reactive or related to the pigmentary trait, drugs       more, the histopathologic evaluation of melanocytic lesions
and some rare syndromes [5]. This broad differential diag-        of the nail matrix is particularly challenging, since early mel-
nosis renders the clinical assessment of melanonychia striata     anoma has only bland histopathologic alterations [12,13].
particularly challenging.                                            Taken all the above into consideration, an accurate clini-
    Among the various possible causes of melanonychia stri-       cal evaluation of melanonychia striata is particularly relevant
ata, melanoma is definitely the most important to be clini-       and valuable in the routine practice. Based on knowledge
cally recognized at the earliest possible stage. Nail melanoma    generated and published in the last decades, we propose
is relatively rare, representing 0.7%-3.5 % of all melano-        herein a seven-step diagnostic approach for melanonychia
mas [6]. Usually, it is diagnosed during adulthood and more       striata longitudinalis aiming to provide succinct, comprehen-
frequently involves the first toe or thumb. Nail melanoma         sive and clinically useful recommendations.
almost always develops in the nail matrix, but, since a large
proportion of matrix is hidden in the proximal nail fold,         Step 1. Hemorrhage First
what is macroscopically visible is a pigmented band on the        In individuals of white skin, subungual hemorrhage is by far
nail plate, originating from the proximal nail fold and ex-       the most common cause of nail plate pigmentation. There-
tending linearly towards the periphery until the distal end-      fore, the “pre-test” probability of blood being responsible
ing of the nail plate. The pathogenesis of nail melanoma is       for nail plate pigmentation is definitely high. Usually, the
poorly understood, unlike other melanoma types the role of        recognition of a subungual hemorrhage is straight forward
ultraviolet exposure is probably minimal, it belongs to the       on clinical and dermatoscopic examination. It is typified by
lentiginous pathology subtype of melanomas (Acral Len-            an initially red-to purple color, sharply demarcated borders,
tiginous melanoma [ALM]) characterized by an initial slow         peripheral blood spots and/or linear distal projections (fila-
growth profile and a little tumor load at early stage. Its evo-   mentous lines). Over time the color often turns brown yet
lution towards a more aggressive and visible tumor with an        the silhouette with a sharp proximal border and distal pro-
ulcerated and nodular, often amelanotic, component occurs         jections does not change. (Figures 1 and 2) [14-16]. More-
after months of years of apparently indolent melanonychia         over, hemorrhages often do not arise from the proximal nail
striata. Prognosis, correlated with Breslow index just like ev-   fold, which helps to exclude melanocytic tumors that always
ery melanoma subtype, is then clearly impaired underlining        develop on the nail matrix and, therefore, result to nail bands
the importance of an earlier diagnosis at the melanonychia        originating from the proximal nail fold (Figure 1).
striata stage. Its genotypic profile very rarely shows BRAF          However, it has to be underlined that the presence of
or NRAS mutations yet CKIT mutations appears to be more           hemorrhage does not exclude the co-existence of a malig-
unusual than initially thought [7,8].                             nant tumor, such as melanoma or squamous cell carcinoma,
    During the last 20 years, dermatoscopy acquired               that might destroy the nail bed and cause bleeding (Figures 3
an invaluable role in the diagnosis of pigmented and              and 4) [17-19]. For this reason, the diagnosis of a subungual
non-pigmented skin tumors, improving the detection of mel-        hemorrhage should prompt clinicians to perform a photo-
anoma and other skin cancers and the recognition of benign        graphic documentation and follow up at a 3-6 months inter-
tumors as well [9]. Indeed, robust evidence confirms that         val in order to monitor the migration, at approximately half
dermatoscopy increases both the sensitivity and specificity       the speed of the nail growth one, of the blood towards the
for melanoma diagnosis [10]. However, biopsy and histo-           distal end and the restitution of the nail plate.
pathologic examination remain the gold standard procedure            Considering that hemorrhage is the most frequent cause,
for lesions that cannot be safely diagnosed on clinical and       the assessment of most nail pigmentations will end at this
dermatoscopic examination. A partial or excisional biopsy         first step. If, however, a hemorrhage cannot be diagnosed
is usually an easy to perform procedure, without significant      with confidence on clinical and dermatoscopic examination,
requirements in time and costs and with minimal morbidity         the evaluation should proceed to step 2.



2                                                                            Opinion | Dermatol Pract Concept. 2023;13(4):e2023204
                   Figure 1. A subungual hemorrhage not arising from the proximal nail fold. Dermatoscopically is it
                   typified by red color, sharp demarcation and satellite blood spots.




                   Figure 2. A subungual hemorrhage arising from the proximal nail fold. Dermatoscopy reveals red,
                   purple and black colors and the characteristic linear hemorrhages at the distal part.




                   Figure 3. A subungual squamous cell carcinoma complicated with hemorrhage.



Opinion | Dermatol Pract Concept. 2023;13(4):e2023204                                                                  3
                   Figure 4. An advanced subungual melanoma that destroyed a significant part of the nail plate and
                   caused hemorrhage.



Step 2. Age Matters                                                  Step 3. Number of Nails Matters
Nail melanoma in childhood is exceedingly rare. Overall, 21          Nail matrix cancer usually involves only one finger or toe.
cases have been reported in the literature, of which only two        Thus, longitudinal melanonychia affecting multiple nails is
in white individuals [20-22]. In most of these case reports,         rather suggestive of a systemic factor that activates nail ma-
the histopathologic diagnosis was equivocal and all but 2 le-        trix melanocytes to produce increased amounts of melanin.
sions were intraepidermal (in situ). There are only 2 reported       One exception is SCC-Bowen that might be polydactylic es-
cases with an unequivocal diagnosis of invasive melanoma             pecially in contiguous fingers in subjects exposed to ioniz-
developing in a Chinese and a Japanese child, respectively. In       ing radiations. Drugs are among the most frequent causes of
large reported series of nail melanoma from referral centers,        activation of nail matrix melanocytes. Drug-induced mela-
no patient was younger than 30 years old [19,23]. A study by         nonychia usually appears 3-8 weeks after the drug intake
Blessing et al on 100 cases of subungual melanoma revealed           and presents as light brown-black longitudinal or multiple
no malignancy in the age group below 30 years old. In an-            transverse bands [27]. Drugs responsible for such changes
other study by Phan et al with 126 cases of acral and nail           include chemotherapeutic agents, hydroxyurea, psoralens,
melanoma, patients age ranged from 28 to 91 years [19,23].           and others [28]. It is usually reversible within 6-8 weeks, al-
In published series of longitudinal melanonychia in children,        though it may persist for months after withdrawal of the
no melanoma case was reported [24]. The latter epidemio-             responsible drug. Melanonychia on multiple nails may also
logic information becomes even more relevant in the light of         result from pregnancy, fungal infections, ethnic pigmenta-
evidence suggesting that congenital subungual nevi might be          tion, Laugier-Hunzkier syndrome or inflammatory disorders
particularly worrisome in terms of their clinical and derma-         [27,29,30]. Whenever assessing a patient with polydactylic
toscopic morphology and also in terms of their growth rate.          melanonychia, it is advised to take a detailed medical history
Nail matrix nevi may be present at birth (congenital), but           that may help uncover the causative factor.
they can also appear during the first years of life (congenital          Similarly to what mentioned above about hemorrhage,
type) [25]. A recently published multicentric cohort study by        it should be underlined that a systemic cause of polydac-
the International Dermoscopy Society found that more than            tylic melanonychia does not exclude the possibility of mela-
half of congenital and congenital-type nail matrix nevi dis-         noma. For instance, since it is well-known that ALM is the
played an irregular pattern of longitudinal microlines, remi-        most common melanoma subtype in dark skin types, an
niscent of subungual melanoma [26].                                  ethnic-type pigmentation of several nails does not exclude
    Therefore, it appears that any pigmented nail band in            that a melanoma or SCC might appear in one of these nails.
children is most likely benign, usually caused by a congenital
nail matrix nevus, even if the lesion is large, dermatoscopi-
cally irregular or extends to the periungual skin (Figures 5         Step 4. Free Edge Matters
and 6) [22]. While many of these lesions may cause anxiety in        Dermatoscopic examination of the free edge of the nail plate
the children parents or guardians, evidence suggests they are        provides additional information that might be clinically rel-
most likely benign and may only require a regular follow-up.         evant. First, it allows a more precise topographic evaluation



4                                                                               Opinion | Dermatol Pract Concept. 2023;13(4):e2023204
                   Figure 5. A 7-year old child with a nail matrix congenital nevus resulting in a melanonychia striata
                   involving almost the entire nail plate and characterized by asymmetry of colors.




                   Figure 6. A 4-year old child with a nail matrix congenital nevus resulting in a highly asymmetric
                   pigmentation of the nail plate that expands also to the skin of the lateral and distal nail fold. The
                   pigmentation of the periungual skin of the distal nailfold is typified by a characteristic fibrillar pat-
                   tern, which typically results for subungual congenital nevi.




of the pigmentation. Specifically, pigmentations involving               Step 5. Brown or Gray?
the upper part of the nail plate probably result from a mela-            If all the aforementioned causes have been excluded in the
nocytic tumor located on the proximal matrix, while those                previous steps, the next step is to try to predict if the pig-
involving the lower part of the nail plate correspond to tu-             mented nail band results from proliferation (melanocytic
mors of the distal matrix [31]. Second, the assessment of the            tumor) or simple activation of nail matrix melanocytes.
free edge might reveal nail plate deformities suggestive of              Although, as described above, activation of nail matrix me-
non-­melanocytic tumors, which, occassionaly, might be pig-              lanocytes is usually polydactylic when resulting from a sys-
mented. For example, detection of localized thickness changes            temic cause, it might also occur in only one digit reactively to
of the free edge of the plate almost excludes “melanocytic”              a previous trauma, infection or other local cause [35].
causes, and the presence of characteristic clues might confirm                Discriminating between a monodactylic melanocytic
the diagnosis of a non-melanocytic tumor such as pigmented               activation and a nail matrix tumor is challenging and der-
onychopapilloma, onychomatrichoma, Bowen disease or                      matoscopy might be of help. A melanocytic proliferation
squamous cell carcinoma [32-34] (­Figures 7 and 9).                      (benign-nevus or malignant-melanoma) usually results to a



Opinion | Dermatol Pract Concept. 2023;13(4):e2023204                                                                                  5
    Figure 7. Dermatoscopy of the free edge reveals a focally thinner nail plate, a hyperkeratotic plug
    underneath the nail plate and a punctate hemorrhage, suggestive of onychopapilloma.




    Figure 8. An onychomatrichoma typified in free edge nail plate dermatoscopy by extensive thicken-
    ing of the nail plate and the characteristic nail pitting or “honeycomb pattern”.




    Figure 9. Free edge nail plate dermatoscopy of this squamous cell carcinoma reveals extensive local-
    ized subungual hyperkeratosis without pitting.



6                                                                   Opinion | Dermatol Pract Concept. 2023;13(4):e2023204
                   Figure 10. A brown color of the nail band is suggestive of a melanocytic tumor of the nail matrix,
                   in this case a nevus.




                   Figure 11. A gray color of the nail band is suggestive of activation of nail matrix melanocytes, in
                   this case reactive to a previous trauma.


brown or black-colored nail band. In contrast, a gray color           should only be considered one-sided, meaning that a wide
of the band is rather suggestive of melanocytic activation            nail band is suspicious for melanoma, but a narrow band
(Figure 10 and 11). In most cases lentigo of the nail matrix          does not exclude an early and still small melanoma of the
(isolated or in the context of a Laugier-Huntziker disease or         nail matrix. Obviously, the size criterion does not apply in
another lentiginosis) the color is also gray.                         childhood, but this was already discussed above. In terms of
                                                                      management, this translates into the following recommenda-
Step 6. Size Matters                                                  tion when evaluating a mododactylic pigmented nail band of
A monodactylic longitudinal melanonychia of brown-black               brown-black color in adults: Wide bands (covering more than
color is probably suggestive of a melanocytic tumor on the            2/3 of the surface of the nail plate should be managed with
nail matrix, either a nevus or a melanoma [1,36]. Before as-          extreme caution and possibly histopathologically evaluated
sessing the dermatoscopic pattern and features of the nail            even if they are not particularly asymmetric, whereas smaller
band, useful diagnostic information derives from its width. A         bands should enter the following step (Figures 12 and 13).
retrospective observational study done by the International
Dermoscopy Society [26] analyzed 82 cases of pigmented nail           Step 7. Regular or Irregular?
bands in adults and reported that an involvement of more              The dermatoscopic features of pigmented nail bands resulting
than ⅔ of the nail plate posed an 8-fold increased probability        from nail matrix nevi and melanoma have been previously
of melanoma. It has to be emphasized that the “size” criterion        investigated [37-39]. Typically, nail matrix nevi produce a



Opinion | Dermatol Pract Concept. 2023;13(4):e2023204                                                                              7
                   Figure 12. Subungual nevi in adults usually result in relatively narrow nail bands that rarely involve
                   more than 2/3 of the nail plate.




                  Figure 13. A melanonychia striata developing in a 55-year old woman. Although the band displays
                  only mild asymmetry, the fact that it involves almost the entire nail plate is highly suggestive of
                  melanoma.



relatively homogeneous band in terms of color that might                contrast, homogeneous and narrow nail bands can be safely
vary from light brown to dark brown or black. In contrast,              monitored, taking into consideration also the last step below.
a pigmented nail band resulting from nail matrix melanoma
is more likely irregular, consisting of parallel lines of vari-         The Last Step: Follow-up or Follow-back?
able width and variable shades of brown, gray or black color            Sequential follow up with digital dermatoscopic images is
(Figure 14). Additional features are the presence of granu-             commonly used in daily practice and was shown to be par-
lar pigmentation and the expansion of the pigmentation                  ticularly useful when appropriately applied. This is because
on the periungual skin of the proximal or lateral nail folds            it provides robust information on the natural biologic evo-
­(Figure 15) that might visible macroscopically (Hutchinson             lution of lesions and, therefore, enables the recognition of
sign) or only dermatoscopically (micro-Hutchinson sign)                 early featureless melanoma while helping to reduce the ex-
[14,38-41]. At a more advanced stage, melanoma may also                 cision rate of benign lesions [42,43]. For the assessment of
cause nail dystrophy and splitting of the nail bed (Figure 16).         pigmented nail bands, follow-up is particularly helpful for
The presence of one or more of the above dermatoscopic                  several reasons. First, as discussed above, obtaining biopsies
features should raise the suspicion of melanoma and prob-               from the nail matrix is technically much more demanding as
ably warrants biopsy and histopathologic examination. In                compared to other anatomic sites. Second, early melanoma



8                                                                                   Opinion | Dermatol Pract Concept. 2023;13(4):e2023204
                   Figure 14. A uniform in color pigmented nail band on the left (nevus) and an asymmetric nail band
                   on the right, consisting of internal lines of different color and thickness (melanoma).




                   Figure 15. The expansion of pigmentation in the periungual skin (Hutchinson sign) is almost al-
                   ways suggestive of melanoma in adults.




                   Figure 16. Onychodystrophy and nail plate loss in a melanoma.



Opinion | Dermatol Pract Concept. 2023;13(4):e2023204                                                                  9
                           Figure 17. Dermatoscopic examination of the nail plate with a melanonychia stri-
                           ata reveals the evolution dynamic within a timeline of a few months back.




might display only bland histopathologic features and perfo-             This study is only conceptual and opinion-based. The re-
ming biopsy of melanomas at a very early stage might results         view of the literature was not performed with a systematic
in inconclusive or false negative histopathology assessments         methodology and all the suggested recommendations should
[11,25,44]. Third, after inconclusive biopsy of a melanon-           be interpreted critically.
ychia striata, dermoscopy follow-up becomes very difficult
since the scar in the matrix (even after a shave biopsy) cre-
                                                                     Conclusions
ates irregular patent of the possible recurrent pigmentation.
Fourth, the presence of blood or other substances (ex. ker-          In this 7-step + 1 approach, we attempted to incorporate
atin) might impede the complete visualization of the nail            available evidence on assessment of melanonychia striata,
plate at the baseline visit. In fact, in the current document,       addressing important issues that influence clinical decision-
follow up has been recommended in several scenarios (eg              making and diagnostic procedures.
hemorrhage, nevi in children, narrow homogeneous bands
in adults).
     The main limitation of this strategy is the obvious need
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