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Animal-type melanoma (ATM) was first described in the literature by Levene in 1979 in relation to a patient with a characteristic clinical presentation, and only later, rare and anecdotal case series have tried to shed light on an entity that has undergone several nosographic classification changes, and which, since 2018, is classified under the term “pigmented epithelioid melanocytoma”. Here, researchers conduct a brief review of the current literature on ATM and present a new clinical case with histopathological, immunophenotypic, and molecular investigations.
Animal-type melanoma is a rare variant of malignant melanoma described for the first time in humans in 1979 by Levene , which took this name by virtue of alleged similarity with equine melanotic disease (in gray horses) . The nomenclatures used over the years have been different and multiform, and the rarity of these entities has further complicated a situation that is already complex in itself . Histologically, ATM is characterized by heavily melanized spindle, dendritic, and/or epithelioid cells and a deep solid and periappendageal growth pattern . In the latest edition of the WHO Skin Tumors, ATM was classified as “pigmented epithelioid melanocytoma” (PEM) and it was strongly advised against using the term “animal-type melanoma” again, as it is a potential source of confusion . Interestingly, in 2010, Ludgate et al. proposed a scheme that divides these lesions into “equivocal” and “unequivocal”, stressing the concept of how the rarity of this entity and of the non-stringent morphological criteria can determine difficulties in the definition, in the correct nosographic classification, and thus in the best therapeutic approach for the patient . In this paper, it is our intention to discuss the history of this entity, to outline the classification changes that have occurred up to the most recent times, and to present a new case of ATM that we have been able to study over the last few months. Finally, in the discussion session, we briefly discuss the different positions taken by the various authors in the literature.
The entry is from 10.3390/dermatopathology8030033
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