Jotirniii of Ctitancotis i'athology I')H4: I I : 8 8 - 9 4

Immunohistologic study of cellular populations ofhistiocytofibromas ("dermatofibromas")

.1. KANtiAKLS, D. SciiMin, and .1. Titivoi.iri

lnserm U 2tl9, Euborutoire de Recherehc Dcrmatologique et Imnuinologic. llopitul E,. Herriot. I.yon.Erunce

Histiocytofihromas (HI ) are benign tununtrs of the skin, the ccllnlar compositionof which is not yet known with certainty. The imnnmohistologic characteristics of 5lesions weie studied by using monoclonal antibodies and an indirect inimuno-fluorescence method. All tumours were found to contain HEA-DR(-H) eells, and,to a minor degree. OKM1( + ) eells. OKT6(-I ) cells w.ere present in the epidermisoverlying (he tumours; however in the HE themselves, no <)Kr6( + ) cells werefound. Ihc presence of IIEA-DR(-f) and OKM1( + ) cells demonstrates that HEcontain cells bearing antigenic charaeterlslies of hislioeytes btit not of Eatigei liuns'cells, and we feel that the term "hisliocytoiibronia" is a more accurate designationtor these lesions than "dermatolibroma".

Acce/ilcil for ptibtication October 25, i')H3

I listiocytolibronias arc relatively common,benign tumours of the skin, first deseribctl byUnna in IS94 under the name of "fibromasimplex" or "fibroma durum". Many otherdesignations have snbsccjtietitly been usetl forthis mcsenchymal proliferation: "fibrome enpastille" (dva t tc 192S), dcrmatofibionia len-ticularc (Schrcus I93tl), histiocytoma (Wor-ingcr & Kviatkowski 19.̂ 2, Scnear & Caio1936), nodular subcpitlernial fibrosis(Rentiers & Montgomery 1949), scletosinghaemangionias ((iross & Wolbach l'-M3). 'Eliemultiplicity of terms leClccts in some way theuncertainty that exists as to the |irccisc natureof Ihc predominant proliletating cells. In fact.

controversy still exists as to whether theseconsist exehisively of fibioblasts, histioeytesor of a mixed, fibro-histiocytic population.

Inmumohistologie techniques have becomea very useful tool for studying skin biopsies( Ihivolet & Eaure 19(S3). The use of monoclo-nal antibodies is parliciilarly helpful in theinvestigation of the antigenic phcnotype ofseveral celhilai iiopiilalions and the character-ization of vaiious cell types. The aim of thepresent work was lo dclcrniine the ccllitlavcomposition of HI' by studying the imniuno-hislologic profile of Ihc cells involved iti theselesions.

r i ; L i . p o i ' u i . A I I O N . S 89

,. ^I O c n . s e p r o l i f e r a t i o n o f o v o i d a n d f u s i f o r m e e l l s in I h e n i i t l - d e r m i s ( H I - ' , x . i (K l ) .

iv la ter ia l and HICIIUKI.S

lesions tliagiioscci clinically as liis-were tctiiovcti under local

, nacs t l i c s i a (xylocatne, 2'X.). All of themdivided inio 2 portions. One was pro-

ssed fcir touline histology while the other^ a s s n a p Ifo/.en in liqtiid tiitrogeti atid stored

_ 2 ( ) " C . I'our micton-thick sections werethen c u t on a cryolomc (^24°C), air-dtied atidfved in cold aeetone (10 miti). The indirectjmniunofluorescence technique was pcr-(• r i i icd as follows; a) incubation of the slideswith monoclonal anlibodies (vide infra) (4,S

Tin, 37°C) ; b) washing in I'BS (pU 7.2) (30min)» '-') inctibalion with lltioiescein-isolhio-

•vanatc-eonjugated secotul-layer atiliserum

(Mel<'y y" ' ' ' anii-motise Ig, dilulion 1:20. ?>i)

^1,.,^ 37"C"); d) washing as in b) above. Coun-

tcrstai i i ing lor nuclei was (hen |ierlornied, by

flooding the sections with a 1:50 soltition ofpropiditim iodide (2 iiiiti). Alter a litial wash-itig in I'HS, the slides were tiiounted iti timdi-lied polyvinylalcoliol meiliuni atid exainitiedutider a Zeiss lltioreseetil niieroseope withepi-ilhunination.

Monoelotial atitibodies used itieluded: a)OK 16 (Ortlio Kung I'hartnaceutieal). react-itig with a surface antigeti of cortical tliy-inocN'les atid human Langcthans' cells (LC)(lithian et al. l')Sl. N4urphy el al. 1981)allhotigh absctil Itom maciophages (Du-betttet et al. 1982). b) OK.M1 (Ottho KungPharmaceutical), reading with a .surface anli-geti ol' cells of hutiian tuotioeytes (Bread et al.IWO), c) BI.2. iirepared by .L Hrochier (In-sertii 11 80, Lyoti) according to the method ofcclltilar hybridi/alion. Ihis monoclonal anti-body reacts with a tnotiotiiorphic HLA-DRanligen (Sclimill e( al. I9,S2).

KANIIAKIS !• r AL.

lablc I.Reactivity pattern of the tumours.

^~^^^^^ CasesMCA ^ ^ ^ ^ ^ ^

BL2(IILA-DR)

OKTfi

OKMl

D++ +11 +D ()

E OD +

2

E-H-h

D-I- +

E4- + +D O

E OD4- +

3

E+.acrosyringium

D + + -^-

E+ +D O

E OD +

4

E+

D+-1-

E+ +D O

E O

5

EO ^

D-(--f

E-t-D O f

E O 1D +

MCA: monoclonal antibodiesE : epidermisD : dermisO : negative labelling+ . +^ or + + + : refer lo the number of labelled LX-IIS (moderate to large)

KisiiKs

Ilistoloi^y

On rotitinc histologic examination, 4 of thelesions were elassified as eellular liis-(iocylofihromas, i.e., they contained a denseproliferation of ovoid and elongated cells,located iti the tnid and lower dermis atidsometimes artanged in a whirl-like pattern(Fig. 1). The overlying epidermis wasacanthotie aiul papillomatous. One ttiniour(Case 3) was a fibrous histioeytofibroma, i.e.,it contained predominantly dense eollagenbundles atnong which some fusiform cellswere interspersed.

Initntinohistoiogy (Table 1)

The results of immunohistology are shownanalytically in Table 1. Generally, sitnilar re-aetion patterns were observed in all eases, a)0KT6: this atitibody revealed a variable nutn-ber of positive, dendritic eells in the epider-tnis. However, no 0KT6( + ) cells cotild bedetected in the dermis in any of the ttimotirs.

and the complete absenee of these eells frotnthe dertnis was in sharp conlrast with theirpresence in the epidermis (Fig. 2). b) OKMl:no positive cells were tevealed by this anti-body in the epidermis. In the dermis a moder-ate number of positive, stellate or fusiformcells was seen (Fig. 3). c) BL2: this antibodyrevealed a varying nutnber of positive dendri-tic cells in the epidermis. BL2( + ) intta-epi-dermal eells were less numerous thatiOKr6( + ) ones. In Case 3, a positive stainitigof the aerosyringeal cells (eells of the ititra-.epidermal part of the eeerine sweat-duet) wasobserved (V'xg. 4).

In the dermis, a latge number of BL2(+)eells could be seen (Fig. 5), and liL2( + ) cellswere mueh more numerous than BL2(-).

Discussion 'R

MF ate telatively comtnon, benign tuniouts ofthe skin ptcsenting as firm, reddish-btowil,asymptotiiatic, single or multiple nodules.They ate histologically characterized hy a

i ioriBUOMA cni.i. POPUI AIIONS 91

2 NiinKTCiis ()K'l"(i( f ) (LangcilKiiis") cells in I he epidermis of ii HI'". In I he derniis no reactivity is seen

fw. 3. Stellate OKMI( + ) eells (anows) in the dermis of Case 4 (x500).

fig. 4. Aerosyritigiutti lahellet l bytnotioelotial ant i lnxly B1.2 (at i t i -H L A - 1 ) R )

Fig. 5. Cellular p to l i le ra t ion in Case 2. Most cells a te labelled hy tnonoclonal an t ibody BL2 ( a n t i - l l L A -l ) k ) . Nuclei of B L 2 ( - ) cells a t e sectt iti the k i t parl of Ihc piclttrc ( ;u tows) .

l lSllOCl'IOl IHROMA CRl I. 93

celluliir prohfcialion of v;iii;ible dcnsily.which has a nodular, ill-defined i;(inriguralionand is located in the mid and lower dermis.The tumour coni|irises fusiform ;uul ovoidcells which are intermingled with collagenfibers. The amount of collagen is more abun-dant in the so-ealled fibrous type than in thecel lular type, in whieli the cellular eornponentpredominates. Small ca|iillaries with promi-pciit endothelial eells are oceasionally found.Special staining reveals in some eases depositsof lipid or hemosiderin within the tumourcells. In some instances nuiltiiuicleate giantcells can also be seen.

Although the clinical and histologie fea-tures of IIF are well known, no unec|uivocal•lereement exists as to the nature of the pro-liferatini; eells. Many authors have supportedtlieir histiocytie tlirierentiation and, theretore,p roposed the term "histioeytoma". Evidencejn favour of this origin came troni experimentscJemonslraling Ihat HI' eells have phagoeytiecapabilities (Senear & Caro 1936). However,other authors on tlie basis of iiltrastrueturalstudies (Mihatseh-Konz et al. 1973) have as-signed a purely fihtoblastie otigin to the tu-mour , supporting the idea that fibrolilastscan, at titnes, develop phagoeytie capacities.j-icnce. the view has been expressed that all••histioeytomas" eonsist of libroblasts andshould, therefore, be called "dermatolibro-mas" (Mihalsch-Konz et al. 197,3).

It is generally kninvn that IILA-DR (ClassII) antigens have, as o|-)posed to HI,A-A, B, C(Class I) antigens, a restrieted cellular dis-tributitin being expressed by certain cell lines(which are generally assoeiated with immunefunctions) and exhihitcd at specific stages ofdifferentiation within other cell lines. SuchiTicsenchytnal cells include principallyU-lymphocytes, activated 1-lymphocytes andcells of the monocyte-macrophage line (Nataliet al. 19^52). Our study showed that the greatmajority of HF cells bear HLA-DR andgens.A generally weaker OKMl activity was also

detected among these cells. The presence ofHLA-DR(-h), OKMl(-h) HF cells is strongcvidenee in favour of their histiocytie dilTeren-tiation. Therefore, we believe that histioeytesare actually involved in the histogenesis ofthese lesions, for which the term "histiocyto-fibroma" should be used in preference to theless aecurate term "derniatofibroma".

The presence of HLA-1)R(+) eells in theaerosyringium (whieh is epithelially deri\ed)is an unexpeeted finding, to which speeialattention should be drawn. Although it has\ery reeently been reported (Ilarrist et al.19S3), this lintling is remarkable, sinee LC andindeterminate cells have so far becti eotisid-ered as the only intraepidermal HLA-DR-beariiig eells. HLA-DR antigens havealso been found on guinea-pig and mousemammary-gland epithelial cells (Klareskog etal. 19,St)), and it has been postulated that theseglands, like other epithelial tissues (small in-testine, salivary glands, respiratory traet),may be involved in ihe homing of IgA-secret-ing plasma eells (Klareskog et al. \9H0). Wehave already undertaken studies to elueidatewhether sweat glands might also he involvedin the development of k>cal immunity.

LC are bone-marrow-derived, imnuino-eompetent cells which show many antigenieaiul functional analogies with histioeytes, suehas presence of Le-IgG and complement reeep-tors, and HLA-DR antigens (StingI & Wolffl9iS3). Therefore, it would seem reasonable toexpect their i^articipation in the eellular popu-lations of lesions whieh, like HF. are charac-terized by a histioeytic proliferation. Ourstudy showed the presence of a relativelylarge number of LC in the epidermis overlyingall 5 I ll'\ However, no LC was seen within thedermal component of the lesions. This findingfurther supports the eoncept that, at the pres-etit time, histiocytosis .X is the uniijue patho-logieal process in whieh a proliferation of LChas been found to occur (Cambazard et al.19,S3).

K A N I l A K I S E l A L .

Ackiiowlcclgcments

We arc grateful to Drs . M. Chal ianon and S.

Euvrard Tor kititlly providing us with surgical

material lor this study.

Rt'lerences

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Adthcss:Dr. ./. Kanilakis.Itisertii U 2(19,1 abotatoite dc RechctchcOcttuatologique et Itnnuttiologie,ilopital E. Heniot-Pav R,69.^74 Lyon Cedex 08,France.