Melanonychia associated with subungual follicular inclusions: report of three cases,

AnBrasDermatol.2020;95(2):217---220

Anais

Brasileiros

de

Dermatologia

DERMATOPATHOLOGY

Melanonychia

associated

with

subungual

follicular

inclusions:

report

of

three

cases

夽,夽夽

Marina

Câmara

de

Oliveira

_,

_Carlos

_Baptista

_Barcaui

_,

_Elisa

_de

_Oliveira

_Barcaui

_,

Juan

Pi˜

neiro-Maceira

a_{DermatologyService,HospitalUniversitárioPedroErnesto,UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,RJ,Brazil} b_{DepartmentofRadiology,FaculdadedeMedicina,UniversidadeFederaldoRiodeJaneiro,RiodeJaneiro,RJ,Brazil}

Received22September2018;accepted12March2019

Availableonline12February2020

KEYWORDS

Dermoscopy; Histology; Nails;

Ultrasonography

Abstract Melanonychiaisthechangeinthecolorationofthenailplateresultingfromthe

depositionofmelanin.Amongitscausesaremelanocytichyperplasia,melanocyticactivation

andnailmelanoma.Subungualfollicularinclusionsarehistologicalfindingsofunknownetiology,

possiblyrelatedtotrauma.Wepresentthreecasesofmelanonychiaofdifferentetiologieswith

subungualfollicular inclusions,anassociationthathasnotbeenwelldescribedandwithan

indefinitepathogenesis.

©2020PublishedbyElsevierEspa˜na,S.L.U.onbehalfofSociedadeBrasileiradeDermatologia.

ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/

by/4.0/).

Melanonychiaisthechangeincolorationofthenailplate, whichvariesfrombrowntoblack,duetothedepositionof melanin.Itsprevalenceisapproximately1%,dependingon ageandethnicity.1_{Themostcommonetiologiesarebenign}

夽 _{How to cite thisarticle: Câmara de OliveiraM, Barcaui CB,}

BarcauiEO,Pi˜neiro-MaceiraJ.Melanonychiaassociatedwith subun-gualfollicularinclusions:reportofthreecases.AnBrasDermatol. 2020;95:217---20.

夽夽_{StudyconductedattheDermatologyService,Hospital}

Univer-sitárioPedroErnesto,UniversidadeFederaldoRiodeJaneiro,Rio deJaneiro,RJ,Brazil.

∗_{Correspondingauthor.}

E-mail:marina co@hotmail.com(M.CâmaradeOliveira).

melanocytic hyperplasia (lentigo and melanocytic nevus), melanocytic activation (racial or drug-induced melanony-chia)andsubungualmelanoma. Fromtheclinicalpoint of view, it can be total or longitudinal (striated). It should be better investigated when it affects only one digit in adults,becauseinthis case melanomais the main differ-entialdiagnosis.1,2

Three cases of melanonychia of distinct etiologies are reported,inwhichhistopathologydemonstratedan associ-ationwithsubungualfollicularinclusions.

These patients sought dermatological care due to changes in nail color and were submitted to dermoscopy (DermLitePhotoPolarizedLightDermatoscopeDL3,3Gen, Dana Point, USA) and high-frequency ultrasound (HFUS), 22MHz (My Lab Touch, Esaote, Genoa, Itátia) showed https://doi.org/10.1016/j.abd.2019.03.009

0365-0596/©2020PublishedbyElsevierEspa˜na,S.L.U.onbehalfofSociedadeBrasileiradeDermatologia.Thisisanopenaccessarticle undertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).

218 CâmaradeOliveiraMetal.

Figure1 HFUS, 22MHz, longitudinalview (Case 3).

Hyper-echogenic,heterogeneousarea with irregular shape(arrow),

avascular,locatedinthenailbedwithDopplermapping.

Figure2 Histopathology(Case1).Epithelialisletswith

ker-atinizationoftheircentralportioninvariabledegree,located

intheconnectivetissueofthenailbed(Hematoxylin&eosin,

×400).

hyperechogenicareaslocatedinthenailbed(Fig.1). Subse-quently,thelesionswereexcisedbyshaveandthematerial sentforhistopathologicalexamination.

Case1:Male,63years,phototypeIII,presenting a lon-gitudinal melanoníquia measuring 3mm in width, in the centralportionofthelefthallux,withevolutionof8months. Irregularbandsofbluishgrayandlightbrownpigmentation wereobservedondermoscopy ofthe nailplate, affecting the entire length of the nail until its free edge. In the histopathologysubungual follicular inclusions were identi-fiedinassociationwithmelanonychia,withoutconcomitant melanocyticlesion(Fig.2).

Case2:Male,43years,phototypeIII,presenting a lon-gitudinal melanoníquia measuring 2mm in width, in the centralportioninthefirstleftquirodactyl,witha3-month evolution.Thepigmentedbanddidnotaffectthedistaledge ofthenail(Fig.3).Shavewasperformedonthenailmatrix (Fig.4)andhistopathology revealed melanocytic nevusin associationwithfollicularinclusions(Fig.5).

Case3:Male,53years,phototypeIII,presentinga longi-tudinalmelanonychiaaffectingtheentirelengthoftheright hallux,withanevolutionof2years.Irregularbandsoflight brownanddarkpigmentationwereobservedondermoscopy of the nail plate, affecting the entire length of the nail untilitsfreeborder,withpigmentleakageattheproximal

Figure3 Clinicanddermoscopy(Case2).Dermoscopyofthe

nailplateshowsirregularbandsoftriangular-shaped

pigmenta-tionwithabluish-graycolorandwiderintheproximalanddark

brownandfinerportionsinthedistalportion.

border(Hutchinson’ssign).Histopathologyrevealed intraep-ithelialmelanocyticdysplasiain associationwithfollicular inclusions.

Subungualfollicular inclusions weredescribed by Sam-man in 1959, involving the toes and, in 1969, the quirodactylsbyLewin.3,4_{Sincethen,ithasbeen described}

withdifferentdenominations,suchassubungualepidermoid cysts,microcystsfolliclesofthenailbed,subungualcalcified inclusions,amongothers.5

Althoughthepathogenesisisunknown,thehypothesisis thattraumaisthemaintriggeringfactor,althoughclinical signs of trauma arenotalways present.4,6,7 _{Some authors}

believethat thereis proliferationof dermal fibroblasts in thenailbed,consequently leadingtosequestrationofthe bedepitheliuminthedermiswithconsequentformationof theinclusions.4,7

Perrinclaims for the use of the term follicular micro-cystsforthesebulbousproliferationsoftheepithelialcones, located in the subungual connectivetissue, usually with-out connectiontothe nail bedepithelium.8 _Hisargument isbasedonfindingsfromtheliteraturewhichindicatethat thenailbedepitheliumhasvestigialfollicularunits,which is justified by the embryological data that the nail bed epithelium isan invaginationof thedorsal epidermis that coversthefingerandcontainsraresprouts,unlikepalmsand plants.We adoptedthe nomenclaturesubungual follicular inclusions, sinceitincludes theargumentofthe follicular originproposedbyPerrin8_{andmaintainspartoftheoriginal}

nomenclature proposed by Samman and Lewin3,4 _because

thereisnotalwaysamicrocysticformationintheepithelial inclusions.

Thehalluxisthemostaffectedfinger,corroboratingwith thehypothesisthattraumaisthetriggeringfactor.5,6_There

Melanonychiaassociatedwithsubungualfollicularinclusions 219

Figure4 Materialobtainedby shaving,and dermoscopyof

the nail matrix (Case 2). After shaving,the material is

sup-portedon paperbefore being placedin theformalin. In the

nailmatrixthereisasmallarea withirregularbandsofdark

brownpigmentationandglobulesintheproximalportion.

Figure 5 Histopathology (Case 2). Junctional nest of

pig-mentedmelanocyticcellsinrelationtoepithelialisletslocated

inthesuperficialconnectivetissueofthenailbed(Hematoxylin

&eosin,×400).

mayassociateditselfasanailclubbing,striations, onychol-ysis,subungualhyperkeratosis,anonychnia,ornoapparent clinicalmanifestation.5,7_{Whenclinicalchangesoccur,they}

areusuallyasymptomaticor, dependingonthesizeofthe inclusions,maycausenailbededema.4,9

Anotherclinicalmanifestationismelanonychia,the lon-gitudinalonebeingthemostcommonlyfoundpresentation. Albeittherearenoreportstoconfirmthehypothesis,itis suggestedthatitisduetotheactivationofthemelanocytes ofthe nailbed.8_{In case 2an associated junctionalnevus}

wasobservedand incase 3therewasa melanocytic dys-plasiawhichisopposedtothetheoryofsimplemelanocytic activation.However,incase1histopathologydidnotreveal melanocytic lesion concomitant with subungual follicular inclusions.

Sometumorslocatedinthenailbedrepresentaclinical differentialdiagnosis,suchaskeratoacanthoma,squamous cellcarcinoma,subungualmyxoidcystandglomustumor.4

Theassociationofsubungualmelanomawithfollicular inclu-sionshasbeenreported,buttherelationbetweenthemhas notyetbeenestablished.5

The histopathological analysis of the nail bed is vital for the diagnosis. Obtaining the tissue for examination is performedafteravulsionofthenailplateandbiopsy. The histopathologicaldiagnosis isbasedonthefindingofislets ofepitheliumlocatedinconnectivetissue,invariable num-berandsize,withpartialorcompletekeratinizationofits centralportion.Theseisletsarenotrelatedtothenailbed epithelium.5,7

Dermoscopy revealed an ‘‘eclipse sign’’, a well-demarcated ring-shaped image that may represent the epithelialisletswithcentralkeratinization.9_{Thisfindingis}

usefultodifferentiatefromothernailtumors,butwasnot foundinanyofreportedcases.

The subungual follicular inclusions can be observed in HFUSashypoorhyperechogenicareaswithirregularshape, locatedin the nail bed, hypoechoic.In Doppler mapping, thestructureis avascular, whichdifferentiatesitself from tumorsofthenailunit.10

Subungualfollicularinclusionsareproliferative, epithe-lial, benign lesions, and often incisional biopsy is both diagnosticandtherapeutic.7

Sincethesubungualfollicularinclusionsare histopatho-logicalfindingspoorlydescribedintheliterature,withnine publishedarticles,itisimportanttoknowmoreaboutthis condition, sinceit can cause differentclinical manifesta-tionsinthenails.

Financial

support

Nonedeclared.

Authors’

contributions

MarinaCâmaradeOliveira:Approvalofthefinalversionof themanuscript;conceptionandplanningofthestudy; elab-orationandwriting ofthemanuscript;obtaining,analysis, and interpretation of the data; effective participation in researchorientation;

220 CâmaradeOliveiraMetal. Carlos Baptista Barcaui: Approval of the final version

of themanuscript; conception and planningof the study; elaborationandwritingofthemanuscript;obtaining, anal-ysis,andinterpretationofthedata;effectiveparticipation in research orientation; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; criticalreview of the literature; critical review of themanuscript.

Elisade Oliveira Barcaui:Approval of the final version of themanuscript; conception and planningof the study; elaborationandwritingofthemanuscript;obtaining, anal-ysis,andinterpretationofthedata;effectiveparticipation in research orientation; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; criticalreview of the literature; critical review of themanuscript.

Juan Pi˜neiro-Maceira: Approval of the final version of the manuscript; conception and planning of the study; elaborationandwritingofthemanuscript;obtaining, anal-ysis,andinterpretationofthedata;effectiveparticipation in research orientation; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; criticalreview of the literature; critical review of themanuscript.

Conflicts

of

interest

Nonedeclared.

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