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Dermatopathology: Practical & Conceptual April - June 2008
5. New Heights: “Animal-type” melanoma and entities related to it (Part I): Evolution of a concept
François Milette, M.D.
A. Bernard Ackerman, M.D.
Contents of Part I
I. Melanosis in horses and men? (Dick, 1832)
II. A précis of equine melanotic disease (Levene, 1971)
III. Melanoma arising in “blue nevi”? (Darier, 1925)
IV. Diffuse mesodermal pigmentation? (Carleton and Biggs, 1948)
V. Melanotic disorders in horses and men? (Levene, 1979)
VI. Pilar neurocristic hamartoma? (Tuthill, Clark, and Levene, 1982)
VII. Malignant melanoma arising in a blue nevus? (Pathy, Helm, Elston, Bergfeld and Tuthill, 1993)
VIII. Cutaneous malignant melanotic neurocristic tumor arising in neurocristic hamartoma? (Pearson, Weiss, Headington, 1996)
IX. Malignant melanoma with prominent pigment synthesis: “Animal-type melanoma”? (Crowson, Magro, Mihm, 1999)
X. Animal type melanoma? (Requena, de la Cruz, Moreno, Sangueza, Requena, 2001)
XI. Animal-type melanoma? (Kazakov, Rütten, Kempf, Michal, 2004)
XII. In the textbooks?
XIII. Melanomas in horses as described in veterinary medicine literature? (Valentine, 1995; Seltenhammer, 2004)
I. Melanosis in horses and men? (Dick, 1832)
According to most authors who have written about animal-type melanoma, Dick was the first to report on that particular condition in horses. [
] The only of those authors who seems actually to have read Dick, however, is Levene (1971). [
] All others cited him incorrectly, as will become obvious from scrutiny of the citations following in the context of what, in fact, Dick truly wrote, his statements, verbatim, coming immediately after these quotations brief:
"Dick, in 1832, was the first author to describe neoplasms comprising nodules of heavily pigmented melanized melanocytes in the skin of gray horses."
"Dick in 1832 coined the term equine-type melanoma . . ."
"Dick reported the existence of skin neoplasms in grey horses consisting of nodules of heavily pigmented cells."
These affirmations, repeated again and again, seem to give legitimacy to the concepts of "animal-type melanoma" and "equine-type melanoma," endowing them with respectability that is conferred by virtue of their having been set forth nearly 175 years ago. But read what Dick really wrote and judge for yourself whether he has been quoted accurately:
"Melanosis in Horses and Men: It is pretty generally known amongst veterinary surgeons that gray horses are peculiarly liable to melanosis; and it appears to me that the disease proceeds, in the individuals in which it occurs, as the animal changes in color from dark to light gray or white. Will you or anyone of your numerous scientific correspondents have the kindness to inform me whether anything analogous occurs in human subject; that is to say, whether persons of dark complexions have been observed to be more liable to this disease as their hair changes to gray or white. If such is found to be the case, it would, I am sure, be interesting to many of your readers, as well as myself. If at the same time it could be ascertained whether the coloring matter of the hair, and the dark coloring matter of the melanosis humour are analogous.
I am, Sir, your most obedient servant
William Dick, V.S.
Apart from the fact that this kind of letter anecdotal would have no chance of being published today, all that can be gleaned from it is that Dick may have been the first to query whether any disease in humans resembles what he called "melanosis" in horses. He did not coin a term of any kind and he made no mention of "neoplasms of heavily pigmented cells." Neither the word "cell" nor the word "melanocyte" appears in his short letter. Dick told only of an observation supposed and asked a question naïve.
Given these facts, citations like those of Requena et al., [
] Kazakov et al., [
] and Mihm et al., [
] are seen to be pure invention and revisionism! In fact, the term "animal- type melanoma" was "coined" in 1999 by Mihm and followers of him*; [
] it is only little more than 7 years old and does not deserve to live longer, as will become obvious as a reader reads on. How surprised Dick would be if he were he to resurrect to find himself credited with the "first description" of any disease! Moreover, the account historical given laconically by Mihm and his acolytes are inexact, a beginning inauspicious thoroughly.
In fact, lesions melanotic in horses were mentioned for the first time in 1809 by Gollety-Latourelle, a French veterinarian working at the Lyon Veterinary School, and, a few years later, in 1813, by Gohier (both cited by Levene 1971 [
]). Those two students of the subject traced the origin of the disease to a single white stallion that died in 1784, almost 50 years before Dick wrote his oft-referred-to letter!
The best description of the disease in horses that engages us here is to be found in Levene's article of 1971. [
] It is summarized now in order to allow understanding better of the discussion that follows.
*In order to be faithful to facts it must be added here that Wallace H. Clark Jr., the mentor of Mihm in dermatopathology and an influence powerful on him, began to speak of "animal-type melanoma" in reference to certain melanomas pigmented extraordinarily by melanin as long ago as the late 1970s, even though he never wrote about the subject, including in his text devoted to melanoma published in 1979 (A. B. A., who was privy, first hand, to the comments of Clark).
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