Twelve dogs with oral malignant melanomas (MM) were evaluated in this study, with demographic details indicating a balanced distribution of gender, age, and weight among various breeds. Tumor locations varied, with diverse surgical procedures being performed, including mandibulectomies and maxillectomies. Lymphadenectomies were conducted, revealing a 16.66% metastatic rate in regional lymph nodes. At the time of surgery, clinical staging identified stages I, II, and III, with most cases having non-infiltrated margins and a high mitotic index. Follow-up revealed local recurrences and metastases, prompting additional surgeries and affecting survival rates. This study reports varying outcomes, with some dogs completing one year without recurrence, while others experienced progressive disease, leading to six oral melanoma-related deaths. The characteristics of melanotic melanoma and amelanotic melanoma are observed in order to study differences between them, the degree of aggressiveness, the mortality rate and the possibility of future therapeutic targets. Although high pigmentation has been correlated with a better outcome, we could not find any significant correlation between survival and achromia. Oral benign melanomas might exist, and this could justify variabilities between stage and survival; however, carefulness is required due to their unpredictable behavior. The findings underscore the complexity of oral melanoma cases and highlight the need for further research on effective management strategies.

Background: Canine oral melanoma (COM) is an aggressive and often fatal neoplasm in dogs, with clinical and molecular similarities to human melanoma. Despite its relevance as a comparative oncology model, the molecular mechanisms underlying COM remain poorly understood. This study aimed to characterize gene expression profiles in COM to identify differentially expressed genes (DEGs), potential biomarkers, and therapeutic targets. Methods: In this pilot study, we performed RNA sequencing (RNA-seq) on tumor and healthy oral tissue samples from dogs. Two independent analytical pipelines—Bowtie2-DESeq2 and HISAT-StringTie-Ballgown—were used to ensure robustness in DEG detection. We also conducted pathway enrichment and isoform-level analyses to investigate biological processes and alternative splicing events. Results: Both approaches identified a core set of 929 common DEGs. Key oncogenic pathways, including MAPK/ERK and cell cycle regulation, were significantly affected, with notable upregulation of BRAF, NRAS, CDK4, and MITF (log2FC = 2.86, p < 0.001). The transcription factor SOX10 and the cytokine IL-33, both previously implicated in melanoma progression, were consistently overexpressed. Additionally, NF1, a known RAS pathway inhibitor, was also upregulated. Isoform analysis revealed novel transcript variants, suggesting a complex layer of post-transcriptional regulation in COM. Many DEGs remained uncharacterized, and chromosomal distribution analysis highlighted potential genomic influences. Conclusions: Our findings provide new insights into the molecular landscape of COM, reinforcing its utility as a model for human melanoma. The identification of conserved oncogenic pathways and novel transcript variants opens avenues for further functional studies and the development of targeted therapies in both veterinary and human oncology.

Primary hepatic masses in dogs represent a heterogeneous group of lesions with variable biological behavior and challenging preoperative characterization. The objective of this retrospective study was to describe the clinical presentation, diagnostic findings, surgical management, and outcome of dogs with primary hepatic masses treated surgically. Ten dogs with resectable hepatic lesions and no evidence of extrahepatic metastasis were included. Clinical records, imaging findings, histopathological diagnoses, treatment, and follow-up data were reviewed. Histopathological diagnoses included hepatocellular carcinoma (n=3), nodular hyperplasia (n=2), lobular hyperplasia (n=1), hepatocellular adenoma (n=1), undifferentiated sarcoma (n=1), osteosarcoma (n=1), and one case without definitive histological diagnosis. Tumor size ranged from 3.3 to 18 cm and was not associated with biological behavior. Preoperative cytology showed poor concordance with final histopathological diagnosis in all sampled cases. Abdominal ultrasound identified solitary lesions in all evaluated dogs, although surgery revealed previously undetected multifocal disease in two cases. Most lesions were located in the right hepatic lobes, differing from the predominance of left-sided lesions commonly reported in the literature. All dogs underwent surgical resection. Two perioperative deaths occurred secondary to postoperative renal failure. In the remaining dogs, surgery resulted in complete remission of clinical signs and prolonged survival, including dogs with malignant tumors. Four dogs remained alive and disease-free at the end of the follow-up period (>730 days). These findings highlight the limitations of preoperative diagnostic techniques for predicting the biological behavior and extent of canine hepatic masses. Surgical resection provided substantial clinical benefit and prolonged survival in most cases, supporting its consideration whenever complete excision is technically feasible.

Primary hepatic masses in dogs represent a heterogeneous group of lesions with variable biological behavior and challenging preoperative characterization. The objective of this retrospective study was to describe the clinical presentation, diagnostic findings, surgical management, and outcome of dogs with primary hepatic lesions treated surgically. Ten dogs with resectable hepatic lesions and no evidence of extrahepatic metastasis were included. Clinical records, imaging findings, histopathological diagnoses, treatment, and follow-up data were reviewed. Histopathological diagnoses included hepatocellular carcinoma (n = 3), nodular hyperplasia (n = 2), lobular hyperplasia (n = 1), hepatocellular adenoma (n = 1), undifferentiated sarcoma (n = 1), osteosarcoma (n = 1), and one case without a definitive histological diagnosis. Tumor size ranged from 3.3 to 18 cm. Both benign and malignant lesions were represented across this size range. Cytological findings were discordant with the final histopathological diagnosis in three dogs, whereas one sample was non-diagnostic due to blood contamination. Abdominal ultrasound identified solitary lesions in all evaluated dogs, although surgery revealed previously undetected multifocal disease in two cases. Six of the ten lesions involved the right medial hepatic lobe, although the small sample size precludes conclusions regarding lesion distribution. All dogs underwent surgical resection. Two perioperative deaths occurred secondary to postoperative renal failure. Among the surviving dogs, clinical status during follow-up was generally reported as improved compared with preoperative presentation, and survival times ranged from 4 to more than 730 days, including dogs with malignant neoplasms. Four dogs remained alive and disease-free at the end of the follow-up period (>730 days). This retrospective case series illustrates the clinical and pathological heterogeneity of primary hepatic masses in dogs. Discrepancies between preoperative assessment and intraoperative or histopathological findings were observed in some cases. Given the small sample size, heterogeneous diagnoses and non-standardized diagnostic workup, these observations should be interpreted cautiously and considered hypothesis-generating.

Ten dogs with oral malignant melanoma were evaluated and treated with surgery, of which four dogs were diagnosed with melanotic melanoma and six were diagnosed with amelanotic melanoma. Serum samples from oral malignant melanoma (OMM) were collected at baseline, the day of the surgery, and every 3–4 months, during which time a clinical examination and chest X-rays were performed. Concentrations of GM-CSF, IFN-γ, IL-2, IL-6, IL-7, IL-8, IL-10, IL-15, IL-18, IP-10, KC-like, MCP-1, and TNFα were quantified. Follow-up samples indicated that after the removal of malignant melanoma, the serum levels of GM-CSF, IFN-γ, MCP-1, IL-18, and IL-2 increased significantly. In contrast, when comparing samples from dogs with OMM to those of patients in remission, the concentrations of IL-7 and MCP-1 were significantly higher in the remission samples than in the OMM samples. Furthermore, when comparing the serum concentrations between the OMM-metastasis samples and those patients in remission, elevated levels of MCP-1 were associated with poorer overall survival due to the development of OMM metastasis. Finally, a comparison of cytokines in the melanotic OMM and amelanotic OMM samples revealed that the amelanotic OMM samples exhibited higher concentrations of IL-6, IL-10, and IL-15 compared to the melanotic OMM samples.