Malignant canine mammary tumours: Preliminary genomic insights using oligonucleotide array comparative genomic hybridisation analysis

- The genomic basis of canine mammary carcinogenesis is poorly understood.
- Oligonucleotide array comparative genomic hybridisation evaluation was performed in 10 malignant tumours.
- There were a variety of genomic aberrations, even within a histologic subtype group.
- Dissimilar genomic profiles were observed in tumours collected at one time from a single dog.

Neoplastic mammary disease in female dogs represents a major health concern for dog owners and veterinarians, but the genomic basis of the disease is poorly understood. In this study, we performed high resolution oligonucleotide array comparative genomic hybridisation (oaCGH) to assess genome wide DNA copy number changes in 10 malignant canine mammary tumours from seven female dogs, including multiple tumours collected at one time from each of three female dogs. In all but two tumours, genomic imbalances were detected, with losses being more common than gains. Canine chromosomes 9, 22, 26, 27, 34 and X were most frequently affected. Dissimilar oaCGH ratio profiles were observed in multiple tumours from the same dogs, providing preliminary evidence for probable independent pathogenesis. Analysis of adjacent samples of one tumour revealed regional differences in the number of genomic imbalances, suggesting heterogeneity within tumours.