Epidemiological Study of Canine Mast Cell Tumours According to the Histological Malignancy Grade

Abstract

The aim of the study was to identify significant relationships between the tumour malignancy grade and dogs' age, breed, sex, size, and location of mast cell tumours (MCTs). MCTs accounted for 13.27% of all diagnosed canine skin tumours. The highest incidence was recorded among Boxers, Labrador Retrievers, American Staffordshire Terriers, and Golden Retrievers. Statistical analysis revealed significantly higher probability of occurrence of the grade I mast cell tumour in the French Bulldog in the head, neck, torso, and limb regions, the grade-II mast cell tumour in Boxer, Doberman, Dachshund, shepherds, and setters in the scrotal region, and the grade III mast cell tumour in Shar-Pei in the axilla region. In the group of the oldest dogs aged 11-16, there was higher risk of development of MCTs grade II and III. Young dogs (aged 2-3 and 4-6) were found to be more prone to development of MCTs grade I. There was no correlation between MCTs grade and dogs' sex and size. To the authors' knowledge this is the first report on statistical relationships between the degree of mast cell tumour malignancy and dogs' phenotypic traits, age and tumour location. This analysis indicate predilections for development of the particular mast cell tumour malignancy degrees in certain dog breeds, age, and anatomical location.

Patient and tumour factors influencing canine mast cell tumour histological grade and mitotic index

“…Boxers have previously been reported to have decreased odds of high‐grade MCTs by Mochizuki et al, which was not replicated by our findings. Increased odds of MCTs being histologically high grade have previously been reported in Shar Peis in Poland by Smiech et al (2017), which is consistent with our findings from our Australian population . Breeds that were reported to have increased odds of high‐grade MCTs by Mochizuki et al included Beagles, Bulldogs, Cocker Spaniels, Poodles, Shih Tzus and Rottweilers.…”

“…Various breed predilections to develop MCTs have been well explored previously, identifying dogs of Bulldog origin in particular to have an increased risk of MCT development . However, as this study identified various breeds displaying increased or decreased risk of a MCT being of high histological grade, it is likely that the genes responsible for MCT development differ from those that influence malignancy.…”

“…Little is known of the relationship between a dog's breed and the association with histological grades of the MCTs they develop. Previous studies have demonstrated that boxers and pugs are more likely to develop low‐grade MCTs, despite the breeds' high MCT prevalence . This indicates that the genetic influences involved with developing MCTs likely differ from the genetic predispositions that influence the tumour's biological behaviour and histological grade.…”

“…There are known breed predispositions for developing canine cutaneous MCTs, suggesting that a genetic component of this disease exists . Breeds that have been reported to have an increased risk of developing MCTs include Boxers, Staffordshire Bull Terriers, Boston Terriers, Labrador Retriever, Golden Retrievers and Pugs . There is a possible but unclear role of sex hormones on the development of MCTs, as desexed animals may be at an increased risk of developing MCTs than entire animals .…”

“…This indicates that the genetic influences involved with developing MCTs likely differ from the genetic predispositions that influence the tumour's biological behaviour and histological grade. The influence of other factors including patient gender, patient neuter status, patient age and tumour location and how they influence MCT histopathological grades have only been previously assessed in two studies, originating from the United States and Poland . To the author's knowledge, the influence of tumour size and the genetic composition of Australia's dog population on MCT histopathological grades are yet to be assessed in the literature.…”