THE AMERICAN JOURNAL

OF PATHOLOGY

VOLUME VM SEPTEMBER, 1932 Nuxm

MELANOMA STUDIES *

I. ThEDOPA REACTION IN GENERAL PATHOLOGY

GEORGE F. TamLAw, M.D.

(From £k Laboraries ofSd De$rlmeu ofSorg, CoLlge of Pkysicias adSgwous, Colmbia Uxiersity, New York, N.Y.)

Introduced in 1917 by the distinguished dermatologist of Zurich,Bnmo Bloch, and defended by him vigorously ever since, t" thedopa reaction has been used chiefly by the dermatopathologist(Becker,'' '7 Peck, 12 anXd Kissmeyer 22) It deserves to bemore widely known and practiced both by the histologist and by thegeneral pathologist. Following the simple method devised by Black-berg, which is descibed in detail in the second paper of this series,the dopa reaction * can be carried out easily and accurately in anylaboratory.The dopa reaction is specific for two kinds of ceRls, for melano-

blasts (a term which indudes all melanin-producing cels as distin-guished from mere phagocytes), and for myelogenous leucocytes(cells which have no known connection with melanin production).Both of these cells contain a ferment, an oxidase, which convertsdopa to melanin. The newly formed melanin colors the cell black.This blackening of the reacting cell is the dopa reaction. The fer-ment of the melanoblast is dopa-oxidase- specific for dopa- itoxidizes nothing else. The ferment of the leucocyte is a polyphenol-o Idase, oxdizing many phenols to colored products.

Figure i shows the dopa reaction of a H kin's lymph node.The black spots are the eosinophil and neutrophil leucocytes.Lymphocytes and collagen are colorless.

Received for publication April 22, 1932." The word "dopa" is Bloch's abbreviation for 3, 4-dioxyphenylalain.

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Figure 2 shows the dopa reaction of normal Caucasian skin. Inthe colorless derma are a few black leucocytes. In most sections ofnormal skin there are a few scattered leucocytes; they have nosignificance. The chief point of interest is the blackening of certaincells in the basal layer of the epidermis and in the matrix of thehair- that is to say- the sites of melanin production. These arethe melanoblasts revealed by the dopa reaction.The menoblasts of the epidermis assume many shapes- round,

cuboidal, columnar and branched. Traditionally the branched cellsof the epidermis are called dendritic. Often they contain melanin,often not. Their common property is the ability to oxidize dopa tomelanin, blackening in dopa solutions. Bloch holds that in this dopa-oxidase which converts dopa to melanin he has discovered the agentwhich manufactures natural melanin in mammalia skin. The dopareaction thus becomes an indicator of the presence of the naturaloxidase. Leucocytes being excepted, it follows that every dopa-positive cell is an active melanoblast.

After many experiments on all sorts of tissue, normal and patho-logical, pigmented and non-pigmented, I accept Bloch's view as themost satisfactory working hypothesis yet offered to explain the pro-duction of melanin in human . The illustrations will show someof the evidence which led to this conclusion.Our material consisted of freshly excised surgical specimens from

many parts of the human body. Our first and fundamental conclu-sion was that, leucocytes being excepted, dopa-positive cells arefound only in those tissues where melanin is being produced, orwhere it can be produced under appropriate stimulation. Thesetissues normally are the skin and the mucous membranes of ectoder-mal onrgin; pathologically they are pigmented moles and malignantmelanomas.*

MELANIN IN EXCESS

Having agreed with Bloch that dopa-positive cells are found onlyin menin-producing tissue, in our next finding we were obliged to

* The pigment of the eye constitutes a speial field which has been little cultivated.Since the dopa reaction requires fresh tissue, or tissue that has been fixed in s per centformalin for five hours at the longest; and since it is cusomary to fix smens of hu-man eye much longer than that, there are practical diffculties in attempting dopa reac-tions with this materiaL A thorough study of the dopa reaction of the embryonic eyewas made by Miescheru

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MELANOMA STUDIES. I

agree with him again that wherever meJanin is being produced inexcess, there the dopa-positive cells are increased in number andoften in complexity of dendrites also. Figure 3 is the dopa reactionOf normal negro sin from the breast. The dopa-positive cells aremore numerous than in the normal Cauan sin of Figure 2. Inthis nego skin most of the dopa-positive cells are round and devoidof dendrites, negativing the common belief that a melanoblast mustbe dendritic. Figure 4 shows circumanal skin from another negro.The dopa-positive cells are numerous; many of them are dendritic.Figure 5 shows the increased number of dopa-positive cells in theepidermis of a dark brown patch of von Recklinghausen's disease inCaucasian skin. All of these melanoblasts are round, without den-drites. Figure 6 shows Cauasian in that has been tanned by ex-posure to X-ray. Here melanin production is very active. The dopa-positive cells of the epidermis are numerous. The many leucocytes inthe conum are an expression of the X-ray dermatitis.Thus, it matters not whether the pigmentation be racial (negro),

or pathologically congenital (von Re usen) or acquired, or areaction to radiation from without (snlight, radium, thorium, X-ray), the incr production of melanin is attended by an increasein the dopa-positive cells.

Figure 7 shows the dopa reaction of a pigmented mole, illustratingBloch's conception of the distinction to be made between active andlatent meanoblasts. This distinction will be discussed under thecaption Latent Melanoblasts. In the upper zone of this mole there isabundant melanin; here the nevus cells are strongly dopa-positive.Passng downward there is less and less melanin and correspondinglythe dopa reaction grows fainter and soon disappears. Three-fourthsof the cells in this nevus are producng no visible melanin; these cellsare dopa-negative. The limitation of melanin production to theupper layers of a pigmented mole is common. It is seen again inFigure 8. In both of these moles the melanin-produacng cells areround and devoid of dendrites.

DENRBc CELLS

The common belief that melanoblasts must be dendritic is an errorcarried over from the frog histology which has long dominated hu-man melanogenesis. It is true that active melanoblasts are oftendendritic, but they are not necessarily so. In the pigmented skins

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and in the moles ilustrated, and in malignant melanomas, the activemelanoblasts may be of any shape- round, cuboidal, stellate ordendritic. The shape of the cell has absolutely nothing to do with itsmelanin-producng power or with its malignancy. Figure 9 showsthe dopa reaction of another pigmented mole removed from the armof a negress. This unusual mole consists exdusively of dendriticcells, all of them dopa-positive. The clinical history of such molesdiffers in no way from that of moles composed of round or othernon-dendritic cells.

METANN ABSENT

Having become convinced that an increase in the number of dopa-positive ceRls goes hand in hand with inceased activity of pigmentformation, we studied the opposite condition -decrease and ab-sence of melanin. Figure io shows the dopa reaction from the edgeof a patch of vitiligo of negro in. On the left is seen normal pig-mented negro epidermis with its dopa-positive cells. Then comes azone of bizarre dendritic cells, as is usual at the margin of pigmen-tation or depigmentation. On the right the oolorless skin begins.Here the dopa-posive cell have disappeared, together with themelanin. This disappearance of the dopa-positive cells in vitiligowas descibed first by Bloch,2 who reported a imilar disappearnceof dopa-positive cels from the hair matrix of graying hair.25

Figure Ii shows the dopa reaction from the edge of a black spot onthe white ear of a guinea-pig. Melanin and dopa-positive cels areabundant in the black spot, totally absent from the white skin.BloCh 7 and his SChool have shown repeatedly that there are no dopa-positive cells in albino skin and that no amount of radiation will elicteither melanin or dopa-positive cells in such skin, although in non-albino skin it is a simple matter to produce both of them by radia-tion (Lutz ¶. Thus, whether the absence of melanin be congenital(albino) or acquired (vitiligo), where there is no melanin there are nodopa-positive cells; or, to put it the other way, where there are nodopa-positive cells no melanin is made.

MELANN REAPPEARS

The final proof that dopa-positive cells are concerned in melaninproduction is that they are the invariable precursors of melanin'sappearance or reappearance. Among dermatologists it is well known

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MELANOMA STUDIES. I

that some patches of vitiligo can be stimulated temporarily to repig-mentation by exposure to radiation (Buschke,27 Buschke and Mul-zer,28 With 29). In such repigmentation of vitiligo, both Bloch andKissmeyer30 have reported that the dopa-positive cells reappearfirst; melanin follows. In my own observations of the repigmenta-tion of scars, this sequence is invariable; it is especially striking innegro skin. Bloch 7' 26 has described the same sequence in the humanembryo, Miescher23 in the eye of the embryo chick, rabbit andguinea-pig, Peck 19 in tanning of human skin by thorium radiation.The dopa-positive cells appear first, melanin next, never in the re-verse order. The inference is that the dopa-positive cells are essentialto the production of melanin.

THE AcANTHoSES

In his early experiments Bloch soon found dopa-positive dendriticcells to be abundant among the epithelium of the acanthoses. Theword is Unna's; it applies to the thickening of the prickle-cell layerof the epidermis seen in psoriasis, papilloma, condyloma and similarlesions. Usually there is no excessive pigmentation, often no melaninwhatever. This observation has been confirmed by all dopa workers.I have seen it repeatedly. In fact, the massing of dopa-positive den-dritic cells a little distance back from the margin of a granulatingwound might be ascribed to the acanthosis always present in thiszone quite as justly as to their being forerunners of pigmentation.

According to Kyrle,31 that rare spirit too early lost to dermato-pathology, the cells of the epidermal basal layer have two functions,melanin formation and proliferation. It seems that stimulation ofeither function increases the number and complexity of the dopa-positive cells. I have been unable to correlate this acanthotic in-crease of these cells with their pigment function. This phase of theiractivity awaits adequate explanation.

MUCOUS MEMBRANES

Among mucous membranes, production of melanin is confined tothose of ectodermal origin. Adachi 82 found melanin in the epithe-lium of the mucous membrane of the cheek, lower lip, prepuce andvagina. He was limited to hand-cut, unstained sections. Using boththe silver and the dopa reaction, Redslob 3 found melanin and dopa-positive cells in normal human conjunctiva, Ramel 34 in normal hu-

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man "buccal mucosa" (site not stated). Becker 16 found both mel-anin and dopa-positive cells in Adaci's locations and added thenormal mucous membrane from the middle of the cheek and fromthe pharynx at the level of the hyoid bone. Laidlaw and Cahn 3

found dopa-positive cells and melanin in normal hmn gum (Fig.12); Laidw (unpubfished) in normal anal cnal. The presence ofmelanoblasts exlains the occurrence of prmary melanoma in thesemucous membranes and also the absence of primary melanoma innon-ectodermal mucous membranes which normaly harbor nomelanoblasts and make no melanin.

In blonds, melanin and dopa-positive cells of the mucous mem-branes are scanty, as they are in blond skin; in the mucous mem-branes of negroes and brunets, they are abundant, an observationalready made by Adachi in regard to melanin. To the naked eye,such a mucous membrane may look pink and without a trace ofpigmentation; nevertheless, on microscopic emination melaninwill be found in abundance. Ramel noted radal pigmentaton of themouth in Tziganes; Cahn observed similar radal pigmentation of themouth in negroes and in a negroid type of Bavanran Jew.

CHROXATOPHORES OF T1 DEIRMA

In the upper layers of the derma of every normally pigmentedskin there are seen cells of various shapes containing melanin. Thesecells never give the dopa reaction. Consequently acoDrding to thedopa hypothesis they contain no ondase and they cannot have pro-duced the melanin which they contain. Often these cells are ob-viously phagocytic; they seize and retain any pigment that happensto enter the skin, such as tattoo pigment, blood pigment and gun-powder. Miescher x proved their phagocytic power for melanin andtheir long retention of it by injecting melanin into living human skinand esing bits of sin at various intervals afterward. To distin-guish them from melanoblasts, these cells are called pigment car-riers, chromatophores.Within certain limitations, to be mentioned presently, the dopa

reaction is the one reliable method of distinguihing the meloblastfrom the chromatophore. This distinction may be seen in any negroskin or pigmented Caucian skin. Miescher 37 and von Albertiniand Walthard u have used the dopa reaction to identify melano-blasts in the metastases of malignant melanoma.

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MELANOMA STUDIES. I

LATErNT (DOPA-NEGATIVE) ELANOBLASTS

The use of the dopa reaction as a speific stain for melanoblastsstumbles over the difficulty that the cell capable of producng mel-ann is not always and everywhere dopa-positive; it does not alwaysontain the oxdase. This is seen readily i pigmented moles andin melaas where broad areas of the tumor are free from visiblemelanin and from dopa-positive cells. Here a negative reactionmeans nothing; only the positive cells count. (The situation is dif-ferent with the chromatophores of ordinary pigmented in. Thou-sands of microscopic sectionsemed by competent dopa workershave never once revealed a positive dopa reaction in the cromato-phores of the upper derma. We may accept them as permanentlylacing the melanin-producing oxidase).

In his first publication, Bloc 1 wrote that in malignant melanomathe cells around the growing margin of the tumor were most apt to bedopa-positive, while many of the cells in the center of the tumor werenegative- an observation confirmed by Miescher n and by vonAlbertini and Walthard.u Both Bloch and Miescher point out thatthe dopa-positive meanobast, whether dendritic or non-dendritic,does not always contai melanin, neither is the melanin-containingcell always dope-positive. These discrepandes are exlaied best byBloch's ferment hypothesis, according to which a distinction must bemade between the oxidase (which carries out the dopa reaction), andthe finished melanin (which does not carry out the reaction). Thedopa-positive factor- the oidase- appears in the cell some timebefore the resulting melanin is visible (see caption Melanin Reap-pears); the melanin itself may remain in the cell long after the oxi-dase has disappeared (Mieschers eperimental injection of melanininto human skin).My own experience is in strct harmony with the ferment hy-

pothesis; but, whatever the explanation, there re the fact thatthe dopa reaction must be used with this precaution, that not all celscapable of producng melanin are at all times dopa-positive. In herstudies of pigmentation of the skin of the embryo and newly borngray mouse, Steiner-Wourlisch ° found that even in this normal,progressive pigmentation the production of melanin is not con-tinuous, and the dopa reaction is not continuously present; there areintervals of rest.

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MONGOL CELLS

These nrbbon-like cells buried deep in the corium over the sacrumand along the backs of infants of all races are true melanoblasts, theonly melanoblasts of mesodermal onrgin in normal hujman skn.Bloch7 and Bahrawy 4 found them to be dopa-positive. As ananomaly I saw them in the neurofibromatous in of von Rekling-hausen's disease from over the sacrum of a Caucan girl i8 years ofage. As shown in Figure 13, they were dopa-positive. They black-ened with silver also, proving their scanty pigment to be melanin.Melanomas arisng from these cells and from their analogues, thecells of blue nevi, are the only melanotic tumors of human skin towhich the name melanosacoma can jutly be applied, a view firstformulated by Darier,42 prompted by a suggestion from Bloch.Not every nevus that looks bluish black conforms histologically to

the TiicheJadassohn blue nevus.0 Even epidermal melanin in thetips of long rete pegs will look bluish and not brown if there is littleor no melanin in the surface epithelium (Fig. 12). Sato ihas made asimilar observation of ordinary nevus nests that were deeply placedin the corium. The diagnosis of blue nevus, and the sequent mela-nosarcoma, should rest on microscopic examination.

SARCOXA AND CARCINOMA

The dopa reaction has no relation to malignancy, as such. Inrepeated tests of various forms of non-melanotic saroma and car-dnoma, I have found the tumor cells to be consistently dopa-negative.

EPnTELOxA

Recalling Kyrle's dictm that the function of the epidermal basalcells is twofold, proliferation and melanin production, it might beexpected that the progeny of these cells in forming an epitheliomawould show some melanoblastic characteristics, espeially sinceacanthosis or thiening of the prickle-ell layer is attended by anincrease in the dopa-positive cells. This expectation is fulfilled. Asin all tumors, function is performed imperfectly and irregularly. Insome epitheliomas I find no dopa-positive cells; the dopa-positivecells of the overlying skin stop some distance back from the edge ofthe ulcer as they do in non-malignant granulatng wounds. In other

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MELANOA SUDIES. I

epitheliomas the dopa-positive cells continue in the surface epithe-li over the tumor, or a few scattered dopa-positive cells are seenamong the tumor epithelia, chiefly in the basal layer. As in theacanthoses, these cels are mostly dendritic. Their presece in anepitheiomna seems to have no significance.

MELANOIS COU

In meanosis coli the tunica propria of the mucosa contains manylarge, round, stellate and spindle cells loaded with yellow-browngranules. In the specimens which I have emined the pigment re-acts like melanin in that the fine granules blaen quickly in silver,while the larger granules require a long tine, perhaps several days.Current opinion is divided as to the nature of the pigment, but isagreed that it has been absorbed from the intesinal contents andphagocytized by these cells. The view that the cells are phagocytesis corroborated by Walthard's" finding them dopa-negative atautopsy.Negative dopa reactions of autopsy material are open to su-picion,

owing to the length of time that necessariy elapses between deathand the immersion of the tissue in dopa. By the kindness of DoctorJanssen, I was able to immerse a specimen of diffuse melanosis ofthe upper part of the rectum in dopa within two hours of its excisionfrom the living body. Microscopically the mucosa presented thetypical appearance of melanosis coli The pigment-bearing cellswere dopa-negative. There were no dopa-positive cells, except poly-nudear leucocytes which abound in this mucosa. I have treatedmany fresh surgical specmens of colon and rectum with dopa andalso tested them for melanin with silver with consistent negative re-sults. The condusion is that there are no melanoblasts and nomelanin in the colon or in the rectum above the mucocutaneousjunction. It follows that the occurrence of prmary melanoma abovethis line is highly improbable. If it occurs, it must spring from mis-placed islands of ectoderm.

THE SILvER CoNTRovEiRsySoon after Bloch's first publications Heudorfer4l declared that

there is nothing specific in the dopa raction and that it merely dupli-cates pigment staining with silver, an assertion endorsed by Lem-

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mel47 and Meirowsky.4 My own expenence, coveng hundreds ofsections of kin stained with various silver techniques, and addi-tional hundreds of dopa sections compared with silver staining of thesame in, agrees absolutely wth Bloch's statement that the dopareaction and the silver reaction are totally different things. To anexperienced dopa worker it is obvious that Bloch's critics have beenmisled by overstained dopa sections. The correct reactions couldnever be mistaken for one another. Silver blackens melanin where-ever found, in the derma as in the epidermis, in meloblasts,phagocytes, and free in the lymph spaces indifferently. If the dopa-positive cells happen to contain melanin they Will stain with siver;otherwise not. Dopa, on the other hand, singles out the activemelanoblasts, leaving the melanin in the resting cells unstained.The only melanin that blakens with dopa is the melanin insideof a dopa-positive cell, on which the dopa-melanin is adsorbed ordeposited.

TEE D LPA NLnM N CONTROVERSY

On the publication of the dopa rection Kreibich dedared thathe had long seacred smilar effects from dimethylparaphenylendia-mm (one of the components of the Schultze-Wimkler formula), a posi-io in which he is supported by Melrowsky,4 who goes even furtherand finds the dopa reaction duplicated by a whole series of easilyoxidizable phenols. After many trials with this most highly praisedphenol of this group, I agree with Bloch n and with Walthard4' thatthis phenol, like silver, stains only the melanin and not the proto-piasm of the cell. Even when the reaction succees, the demonstra-tion of the dendritic cells is far inferior to that of the dopa reaction,as Meirowsky himself admits.

TIE MAST CELL CoNroviERsy

Of the many controversies prompted by the dopa reaction, theoddest and the least necessry would seem to be the difference ofopinion of equally well qualified observers over the reaction of mastcells. That mater of dermatopathology, P. G. Unna, wrote long agothat mast cells abound in the snout of the white rat and in humanneurofibroma. It is a simple matter to erse fresh frozen sectionsof these tissues in dopa solution and counterstain them with cresyl

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MELANOMA STUDIES. I 487

violet. In such sections it is seen beyond any possible doubt thatBloch scores once again. The mast cell, both in the white rat and inhumnn neurofibroma, is dopa-negative The reader may see this forhinself in Figures 5 and 13, from the same von Recklnghausenneurofibroma. These sections contain myriads of mast cells, not oneof which has become visible in the dopa solution.

SUMARY

i. Bloch's dopa doctrine is endorsed as the best working hy-pothesis of melanin production in human skin.

2. The dopa reaction is indispensable in the study of pigmentedmoles, melanoma and the movements of melanin.

3. In the identification of melanoblasts with the dopa reaction,only the positive cells are significant.

4. The appearance of dopa-positive dendritic cells in non-pigmented acanthoses remains unexlained.

5. In the controversies which have arisen over the dopa reaction,Bloch's histological findings are corroborated.

In conclusion I must than Professor Bloch for his kindness insending me a portion of his dwindling store of dopa in the beginningof these studies t years ago; Dr. S. N. Blackberg of the Depart-ment of Pharmacology, who showed me how simple a matter thedopa reaction could be made to be; Dr. Jerome Webster for manyfresh specimens from his plastic surgery clinic; and Professor PurdyStout who generously places his choicest material at my disposal.

REFERENCES

i. Bloch, B., and Ryhin&r, P. H ische Studim inmbedebendenGewebe; iiber fementative Oxydation und P tbidung. Ztscr.f. d.ge. cpr. Had., 1917,5, 179-263.

2. Bloch, B. C e Untrmhugen bef das pzifiEhe pgmentidndeFement der Haut, die Dopaoxydase- Zsds.f. Pkysid. Che.w, I9I6-I7,98, 226-254.

3. Bloch, B. Das Pmblem der Pigmntbildu in der Haut Arc/. f. De4.u. SYPk., 19I7, 124, 129-208.

4. Bkc, B., and Loefile, W. Untemschungen Ober die Bronzefirbng derHaut bei Adison'sch Krankrheit. lDchs Arck.f. klix. Hcd., 1917,1I2, 262-29i.

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S. Bloch, B. Zur Kritik der Dopalebre Arch.f. Dermal. u. Syph., I921, I36,23I-244.

6. Bloch, B. Zur Chromatophorenfrage. Drmxat. Ziscr., 1921, 34, 253-262.7. Bloch, B. Nouvelles r sur le problme de la pigmentation dans la

peau. BuU. Soc.fraxsn. de dermat. cd sypk., 1921, 28, 77-96.8. Bloch, B. Der jetzige Stand der Pigntlehre. Zentraibl. f. Haut- u.

Gcsckiskr., 1923, 8, 1-10.9. Bloch, B., and Schaaf, F. Pigmentstudien. Biokem. Ztscdr., 1925, 162,

i8I-2o6.Io. Bloch, B. Les naevo-carcinomes Paris mi., 1925, 55, I6I-I71.ii. Bloch, B. Ueber benigne, nicht naevoide Meaitheiome der Haut,

nebst 8 inber das Wesen und dieGe der Dendritenzellen.Arcs. f. Deraw. u. Syph., 1927, 153, 20-40.

12. Bloch, B. Das Pigment. Jadassohn's Handbuch der Haut- und Gesch-lechtslrankheiten. Berin, 1927, I, part I.

13. Bloch, B. The problem of pigment formation. (Harvard Iecture.) Am. J.Hf. SC., 1929, I77, 6o9-6i8.

14. Bloch, B., and Peck, S. M. Der Nachweis der Oxydase in den Z7dlen desmyeoishen Syst durch 3, 4-DioxYPhenylaanin (Dopa). Foliahwmau., 1930, 4!, I66-173.

I5. Bloh, B., and Schaaf, F. Ueber die P ethdung in der Haut, unter be-sonderer Ber}cksichdgung der optischen Spezifitit der Dopaoxydase.Klin. Wchnschr., 1932, II, 10-14.

x6. Becker, S. W. Melanin pigmentation and dendritic cells. Arch. Derma.Sypk., 1927, I6, 259-290.

17. Becker, S. W. Cutaeous melanoma Arch. Deat. & Sypk., 1930, 21,818-835.

i8. Peck, S. M. Zur Pigmentgenese in der Haut und den Haaren von Kanin-chen. Arch. f. Dermal. u. Sypk., 1929, '57, 234-263.

ig. Peck, S. M. Pigment (nin) studies of the humn skin after applicationof thorium-X. Arch. Dermat. & Syph., 1930, 21, 916956.

20. Peck, S. M. The m c pigment in the skin, hair and eye of the grayrabbit. Arch. Dermat. & Syph., 1931, 23, 705- 729.

21. Kissmeyer, A. Der Herkunft der Naevuszelle, durch das Dopa-Ver-fahren beleuchtet. Arc. f. Dermat. u. Syph., I921, 130, 478-483.

22. Kissmeyer, A. Etudes sur les naevi pigmentaires de la peau humaine.Pans, 1927.

23. Mi , G. Die P entg ese im Auge, nebst Bemerkungen uber dieNatur des Pigmentkorns. Arch. f. mikr. Anal., 1923, 97, 326-396.

24. Bloch, B. Zur Pathogenese der Vitiligo. Arck. f. Dermal. u. Syph., 1917,124, 209-232.

25. Bloch, B. Ueber die Entstehung deHHaut- und Haarpigments beim men-schlichen Embryo und das Erk6schen der Pigmentbildung in ergrauten

MELANOMA STUDIES. 489

Haar (Ursache der Canities). Arc. f. Doat. u. Syph., 1921, 135, 77-I08.

26. Lutz, W. Zur Kennfnis der Wikung der Stahblen auf dieHaut, mit spler B sigung der P t dung. Arch. f.DImat. u. SSYh., 1917, 124, 233-296.

27. Buschke, A. Notiz zur Behang des Vitiligo mit Licht. Med. Kim..1907,3, 983-984.

28. Buschke, A., and MUl, P. WeitereB htungen iber LihtpigmntBerl. klsi. Wchshr., 1907,44, 1575-I576.

29. With, C. Studies on the effect of lgt on vitiigo. Brit. J. Delat., 1920,32, I4S-I5S.

30. mer, A. Studies on pigment with the dopa eaction, ialy ncases of vitligo. Brit. J. Dlnnat., I920, 32, S6-i62.

31. Kyre, J. Vorlsungen fiber die Histo-Biolog der menschlichen Haut undlhrer ErkrankungaL Wien und Berinm. 1925, I.

32. Adachi, B. Hautpigment beim Me und bei den Affen. Zsr. f.Morphol. u. Axthrop., I903, 6, 1-131.

33. Re , E. Etude sur le pDignCt de l'Eithf6im c tval et co.e.Ann. d'ocui., 1922, '59, 523-537.

34. R Mel, E. La p tation de la muqueuse buccale interpr6t& par ladopa-r&actiL Deuiime Congres d. dermat. et. syph. de langue fan-Cazse. StlaSbourg, 1923,408-409.

35. Laidlaw, G. F., and Cahn, L. R. Mdanobasts of the gum. J. Dent. Re-search., 1932, 12, 534-537-

36. Mie er,G. Chromatophoreinder Hautdes Menash Arch.f.Deia.u. Syph., 1922, '39, 313-425.

37. MieM e, G. Ein Beitrag zur epithelialn Genese der malignen Meanomeder Haut. Ceuralb. f. aUg. PatkO. U. path. Anat., I9I9, 30, 353-364.

38. von Alertini, A., and Walthard, B. Ueber genae MlanomatosisundM nosis mit Be tigug der Doparmktion. Fraxk-furt. Ztscir. f. Path., I927, 35, 22-47.

39. Meh,, G. Die Entstung der b6sarigen Mdamome der Haut. Vir-chdws Arch. f. Path. Anat., 1927, 2, 86- 42.

40. Steiwer-Worlisch, A. Das meanotsche Piment der Haut bei der grauenHausmus. ZtSCkr. f. Zdlforsch., 1925, 2, 453-479.

41. Bahawy, A. A. Ueber die Mongollieck bei EUnropier Ein Beitrag zurPigmentlere. Arch. f. Demat. U. Syph., 1922, 1, 17I-192.

42. Darier, J. Lem me maln mE ymat O mno-sarcome. Bull.Assoc. franf. p. l'sude du cancer, 1925, 4, 221-249.

43. Tiche, M. Ueber benigne Meanome (" Chromatophorome") der Haut"blaue Naevi." Virckows. Arch. f. path. Axat., I906, I86, 212-229.

44. Sato, K. Beitrag zur Kenntnis des "blauen Naevus." Diat. Wchnsckr.,1921, 73, 1073-IO77-

490 LAIDLAW

45. Walthard, B. Zur Dopafrage. Frakffrt. Ztsckr. f. Pat/., I926, 33, 141-I58.

46. Heudorfer, K. Untersuchungen iiber die Entstehung des Oberhautpig-ments und dessen iehungen zur Addison'sche Krankheit. Arck. f.Drmwt. u. Sypk., 1921, 134, 339-369.

47. Lemmel A. Die Bedeutung der Dopaeaktion fOir die Berteilung derManom Cetrab. f. aUg. Patsot. u. patk. Axat., 1921, 32, 89-92.

48. Meiowsky, Baar and BauL. Die gegenwirtige Stand der P tfrage.ZistraTh. f. Haut- u. Gescekkskr., 1923, 8, 97-109.

49. Krelbi, C. Zur Bloch's Dopareaktion. Drwat. Wc/nsc/r., I9I8, 66,193-I95-

DESCRIPTION OF PLATES

PLATE 83

All figures are untoucied photomicrographs of dopa reactions at pH 7. 4 andat 37TC for from 3 to 4 hours.FIG. I. Hodgkin's lymph node Myeogenous leucocytes blak; lymphocytes

and coloFIG. 2. Normal CaUcsian skin from breast In the basal layer of the epidrmis

the are blackened sts of vious shapes, both romd and de-dritic. They are few in number and spaced far apart. The ret of the epi-thelium and re cols

FIG. 3. Normal negro skin from breast In the epides the dopa-positecells (ma ) are mre num ous than in Fig. 2. Almost all of themare round, not d itic. The chromtophoes of the corium are viible as

gry spindle cells. They contain no ferment and do not black indopaL

AxCAN~ JOURNAL OF PATHOLOGY. VOL VrIII

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PLATE 84

FIG. 4. Normal crcumanal skin from another negro. The dopa-positive cells ofthe epidermis are very black, very numerous and most of them are dendri-tic. In this corium there are many chromatophores loaded with melanin;none of them blacken in dopa.

FIG. ;. Dark brown patch of von Recklinghausen pigmentation of Caucasianskin. 'Melanoblasts of the epidermis verv numerous. Almost all of them areround, a few are dendritic.

FIG. 6. Caucasian skin tanned by X-ray. Dopa-positive cells of the epidermismuch more numerous than in the normal epidermis of Fig. 2. In the papil-lary layer of the corium there are many black leucocytes, an expression ofthe X-ray dermatitis.

AMERICAN JOURNAL OF PATHOLOGY. VOL VII

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PLATE 85FIG. 7. Pigmented mole. In the center is a hair in its follicle. There is much

melanin in the upper lavers of the mole and here the nevus cells are stronglydopa-positive, very black. Passing downward the melanin decreases andcorrespondingly the dopa reaction becomes fainter. In the lower part of themole, where no melanin is being produced, the nevus cells are dopa-negative.

FIG. 8. Another pigmented mole with the same features as Fig. 7. In both ofthese moles the active melanoblasts, the nevus cells, are round and freefrom dendrites.

AcA JORNAL OF PATHOLOGY. VOL Vm PLATE 85

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LMelanoma Studies. IILaidlaw

PliTE 86

FIG. 9. Unusual pigmented mole consisting entirely of dendritic cells. all ofthem dopa-positive. From the arm of a negress.(FIGS. 5, 7. 8 and 9 from patients of Dr. WN-ebster.)

FIG. IO. Margin of patch of vitiligo of negro skin. On the left. normal negroepidermis with abundant melanin and dopa-positive melanoblasts. In themiddle, the zone of bizarre dendritic cells usually seen at the margin of ac-tive pigmentation or depigmentation of the epidermis. On the right, thecolorless epidermis; both melanin and dopa-positive cells have disappeared.(Patient of Dr. 'Marie Karelitz.)

FIG. ii. Edge of black spot on white ear of guinea-pig. In the epidermis of theblack spot, melanin and dopa-positive melanoblasts are abundant; they aretotally absent from the epidermis of the white skin. At the margin of theblack spot, where melanin becomes scanty, the outline of the dendriticmelanoblasts is seen more clearly.

AmAC N. JOUNAL OF PATHOLOGY. VOI. XIII PLATE 86

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PLATE 87

FIG. I 2. Slate-colored pigmentation of gum of Latin-American; black hair, darkeyes. In the middle third of the very thick stratified epithelium there aremany dopa-positive dendritic cells. The melanin itself is situated chiefly inthe lower end of the very long, slender rete pegs. The deep situation of themelanin and the absence of superficial pigment accounts for the blue colorof the gum, although the melanin is exclusively in the epithelium and not inthe corium, as in the Tieche-Jadassohn blue nevus. An X mark has beenplaced just below the tips of the longer rete pegs. (Patient of Dr. LesterCahn.)

FIG. 13. Dopa-positive -Mongol cells. Neurofibromatous skin in von Reckling-hausen's disease from over the sacrum of Caucasian girl (Polish Jew) i8years of age. The corium is very thick, averaging 1.5 cm. The groups ofribbon-like cells are situated deep in the corium, in its middle or lower third.They are filled with fine granules of melanin. (Patient of Dr. WVebster.)

AmERIcA.N. JOURNAL OF PATHOLOGY. VOL VIII

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