*Editorial* **Veterinary Comparative Pathology, a Scientific Tool for a Thriving Planet**

**Alejandro Suárez-Bonnet 1,\* and Gustavo A. Ramírez Rivero 2**

	- **\*** Correspondence: asuarezbonnet@rvc.ac.uk

In recent years, Earth has overcome unpredictable challenges. From drastic climate change to a viral pandemic of probable zoonotic origin, these concurrent events have raised, to an unprecedented scale, the awareness that the natural world dominates humankind and not vice versa.

Where does veterinary pathology fit in this storm of events? More than a century ago, Virchow Robins, the son of a butcher and often seen as the founder of modern medicine and pathology, and other contemporary scientists like Robert Koch and Louis Pasteur, worked with an enviable mind on diseases that affected both animals and humans. William Osler, a human physician, also studied parasitic diseases in animals and named the parasite *Oslerus osleri* a nematode of canids. In fact, we owe the term 'One Medicine', the precursor of 'One Health', to Dr. Osler. As science used to be more open and scientists considered the natural world, human beings, and nonhuman animals as one, the concept of 'One Medicine' may have naturally developed. In contrast, current medical, biomedical, and basic research works focus on their individual areas, overlooking the bigger picture of the 'One Health' concept.

In this Special Issue, now edited as a book entitled *Comparative Pathology and Immunohistochemistry of Veterinary Species*, the reader can find pathology-focused, rigorously peer-reviewed manuscripts on different aspects of veterinary pathology from a comparative pathology perspective with a particular focus on immunohistochemistry as an ancillary diagnostic tool and a complementary technique in pathology research.

As veterinary pathologists, we have broad knowledge of disease processes in various species with variable physiology and response to disease. The variety of areas where comparative veterinary pathology will elucidate the pathogenesis of vertebrate and invertebrate animal diseases is as wide as the number of diseases, aetiologies, and species known by science, whether they are neoplastic, infectious, non-infectious, or environmentally related.

Comparative pathology, or as we prefer to call it, 'One Pathology', is the cornerstone of biomedical sciences and, ultimately, veterinary and human medicine. Only if we understand that there are no physical or philosophical boundaries between species, diseases, and the natural world and that they are, in reality, related and causally linked will we be able to unveil the secrets to a healthier planet.

**Conflicts of Interest:** The authors declare no conflict of interest.

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**Citation:** Suárez-Bonnet, A.; Ramírez Rivero, G.A. Veterinary Comparative Pathology, a Scientific Tool for a Thriving Planet. *Animals* **2023**, *13*, 1504. https://doi.org/10.3390/ ani13091504

Received: 5 April 2023 Revised: 19 April 2023 Accepted: 26 April 2023 Published: 28 April 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

*Article*

## *KIT* **Somatic Mutations and Immunohistochemical Expression in Canine Oral Melanoma**

**Ginevra Brocca 1,\*, Beatrice Poncina 1, Alessandro Sammarco 1,2, Laura Cavicchioli 1 and Massimo Castagnaro 1**


Received: 9 November 2020; Accepted: 7 December 2020; Published: 10 December 2020

**Simple Summary:** Malignant melanomas arising from mucosal sites are very aggressive neoplastic entities which affect both humans and dogs. The family of tyrosine kinase receptors has been increasingly studied in humans for this type of neoplasm, especially the gene coding for the proto-oncogene *KIT*, and tyrosine kinase inhibitors are actually available as treatment. However, *KIT* alteration status in canine oral melanoma still lacks characterization. In this study, we investigated the mutational status and the tissue expression of *KIT* through DNA sequencing and immunohistochemical analysis, respectively. A homogeneous cohort of 14 canine oral melanomas has been collected, and while tissue expression of the protein was detected, no mutations were identifiable, most likely attributing the dysregulation of this oncogene to a more complex pattern of genomic aberration.

**Abstract:** Canine oral melanoma (COM) is an aggressive neoplasm with a low response to therapies, sharing similarities with human mucosal melanomas. In the latter, significant alterations of the proto-oncogene *KIT* have been shown, while in COMs only its exon 11 has been adequately investigated. In this study, 14 formalin-fixed, paraffin-embedded COMs were selected considering the following inclusion criteria: unequivocal diagnosis, presence of healthy tissue, and a known amplification status of the gene *KIT* (seven samples affected and seven non-affected by amplification). The DNA was extracted and *KIT* target exons 13, 17, and 18 were amplified by PCR and sequenced. Immunohistochemistry (IHC) for KIT and Ki67 was performed, and a quantitative index was calculated for each protein. PCR amplification and sequencing was successful in 97.62% of cases, and no single nucleotide polymorphism (SNP) was detected in any of the exons examined, similarly to exon 11 in other studies. The immunolabeling of KIT was positive in 84.6% of the samples with a mean value of 3.1 cells in positive cases, ye<sup>t</sup> there was no correlation with aberration status. Our findings confirm the hypothesis that SNPs are not a frequent event in *KIT* activation in COMs, with the pathway activation relying mainly on amplification.

**Keywords:** Canine oral melanoma (COM); copy number aberration (CNA); dog; immunohistochemistry (IHC); single nucleotide polymorphism (SNP); receptor tyrosine kinase (KIT)
