Prevalence and risk factors for mast cell tumours in dogs …

StephanieJWShoop1, StephanieMarlow2, DavidBChurch3, KateEnglish4, PaulDMcGreevy5, AnnelieseJStell3, PeterCThomson5, DanGONeill2 and DavidCBrodbelt2

Canine Genetics and Epidemiology20152:1

DOI: 10.1186/2052-6687-2-1

Shoop et al.; licensee BioMed Central.2015

Received: 25June2014

Accepted: 18November2014

Published: 26January2015

Mast cell tumour (MCT) appears to be a frequent tumour type in dogs, though there is little published in relation to its frequency in dogs in the UK. The current study aimed to investigate prevalence and risk factors for MCTs in dogs attending English primary-care veterinary practices.

Electronic patient records from practices participating in the VetCompass animal surveillance project between July 2007 and June 2013 were searched for MCT diagnosis. Various search terms and standard diagnostic terms (VeNom codes) identified records containing MCT diagnoses, which were evaluated against clinical criteria for inclusion to the study. MCT prevalence for the entire dataset and specific breed types were calculated. Descriptive statistics characterised MCT cases and multivariable logistic regression methods evaluated risk factors for association with MCT (P<0.05).

Within a population of 168,636 dogs, 453 had MCT, yielding a prevalence of 0.27% (95% confidence interval (CI) 0.24% - 0.29%). The highest breed type specific prevalences were for the Boxer at 1.95% (95% CI 1.40% - 2.51%), Golden Retriever at 1.39% (0.98% - 1.81%) and Weimaraner at 0.85% (95% CI 0.17% to 1.53%). Age, insurance status, neuter status, weight and breed type were associated with MCT diagnosis. Of dogs of specific breed type, the Boxer, Pug and Staffordshire Bull Terrier showed greater odds of MCT diagnosis compared with crossbred dogs. Conversely, the German Shepherd Dog, Border Collie, West Highland White Terrier, Springer Spaniel and Cocker Spaniel had reduced odds of MCT diagnosis compared with crossbred dogs. No association was found between MCT diagnosis and sex.

This study highlights a clinically significant prevalence of MCT and identifies specific breed types with predisposition to MCT, potentially aiding veterinarian awareness and facilitating diagnosis.

Confidence interval

Electronic patient record

Mast cell tumour

Veterinary nomenclature.

Mast cell tumour (MCT) is the most common skin tumour type in dogs, but little is known about its frequency in the general dog population nor its frequency in particular dog breeds in the UK. This study has investigated the frequency of the disease, and possible risk factors associated with the development of MCT.

This has been conducted by analysing the large number of electronic patient health records contained within the VetCompass animal surveillance project collected between July 2007 and June 2013.

Data were available on a population of 168,636 dogs and within this 453 (0.27%) had MCT. The breeds with the highest breed specific prevalences were Boxer, Golden Retriever and Weimaraner. Conversely, some breeds appeared to be protected.

Age, insurance status, neuter status, weight and breed type were associated with MCT diagnosis. No association was found between MCT diagnosis and gender.

Such information helps to increase awareness of this condition, particularly in certain breeds, to owners and veterinarians.

Mast cell tumours (MCTs) are a frequent tumour type in dogs [1], accounting for 7-21% of cutaneous tumours diagnosed [14]. Dobson and others (2002) reported the incidence of MCT in English dogs as 129 in 100,000 dogs per year [5]; however, this study was limited to insured animals and thus may generalise poorly to the wider population of dogs in England. MCTs occur primarily in the dermis and subcutaneous tissues and can be confirmed in 92-96% of cases through fine needle aspirate (FNA) cytology [6]. Histopathology allows description of the degree of MCT malignancy and clinical grading [6] using two grading systems. Using the Patnaik system, MCTs are categorised into three grades (I, II & III), the third being more clinically important because tumours of this grade are often more aggressive and may metastasise [7]. The more recently proposed Kiupel two tier system categorises MCTs into high or low-grade in order to increase concordance among veterinary pathologists [8].

There are likely to be many factors contributing to the development of MCT which may be genetically influenced [6]. Up to 40% of dogs with subcutaneous and cutaneous MCTs have been found to have mutations in a proto-oncogene, c-kit[6]. Other potential factors include neuter status, sex, age, weight, insurance status and specific breed types. Females [9], and particularly neutered females [10] have been associated with increased risk of MCT in some studies, although other studies failed to identify an association between sex and MCT [11, 12]. While the mean age at presentation of cutaneous MCTs has been reported at between 7.5 and 9years old [9], one study found poorly differentiated (grade III) tumours more common in younger dogs, although the study population consisted of only one breed, the Shar-Pei [13]. Likewise, while one study found no difference in pre-disposition to MCTs between dogs of specific breed types and mixed breed (crossbred) dogs overall [14], certain breed types have previously been associated with this condition. Most commonly, Boxers and Golden Retrievers [10, 15, 16] and other larger breed types have been associated with pre-disposition to MCT whereas smaller breed types are reported to be at lower risk of the condition [10]. Less commonly, breed types including Pugs [10, 17], Weimaraners [15, 16] and the mastiff and terrier phylogenetic clusters [10] have also been associated with having MCTs.

This study aimed to estimate the prevalence and explore risk-factors for the development of MCTs in dogs, using a large sample of animals attending primary-care veterinary practices in England. By identifying factors associated with a higher risk of developing MCTs, it was hoped to improve the index of suspicion for this disease and hence early recognition of this important condition.

The VetCompass system documented 168,636 dogs from a total of 94 veterinary practices within England between 28

June 2007 and 30

June 2013. Of these, 453 dogs met the clinical criteria for inclusion to the study and were classified as dogs presenting with MCT at a participating veterinary practice during the study period. Thus, the MCT prevalence was estimated at 0.27% (95% CI 0.24% to 0.29%) over the study period. Individual breed type MCT prevalences that exceeded this overall estimate included that of the Boxer at 1.95% (95% CI 1.40% to 2.41%), the Golden Retriever at 1.39% (95% CI 0.98% to 1.81%), the Weimaraner at 0.85% (95% CI 0.17% to 1.53%), the Labrador Retriever at 0.72% (95% CI 0.58% to 0.85%), the Staffordshire Bull Terrier at 0.51% (95% CI 0.39% to 0.62%) and the Pug at 0.50% (95% CI 0.13% to 0.88%). Individual breed-type MCT prevalences that fell below the overall estimate included the Springer Spaniel at 0.20% (95% CI 0.06% to 0.35%), the Jack Russell Terrier at 0.16% (95% CI 0.09% to 0.23%), the West Highland White Terrier at 0.07% (95% CI 0.00% to 0.15%), the Border Collie at 0.07% (95% CI 0.00% to 0.14%), the Cocker Spaniel at 0.06% (95% CI 0.00% to 0.12%), the Yorkshire Terrier at 0.04% (95% CI 0.00% to 0.09%) and the German Shepherd Dog at 0.02% (95% CI 0.00% to 0.05) (Table

A). Overall MCT prevalence for dogs of specific breed types was 0.29% (95% CI 0.26 0.32%) and overall crossbred prevalence was 0.18% (95% CI 0.14 0.22) (Table

B).

Breed-type specific prevalence of mast cell tumour (MCT) diagnosis with 95% confidence intervals (CI)

A) Specific breed types

Breed-type

Cases (n)

Total (n)

MCT prevalence (%)

95% CI (%)

Boxer

47

2406

1.95

1.40 - 2.51

Golden Retriever

43

3086

1.39

0.98 - 1.81

Weimaraner

6

705

0.85

0.17 - 1.53

Labrador Retriever

106

14781

0.72

0.58 - 0.85

Staffordshire Bull Terrier

72

14219

0.51

0.39 - 0.62

Pug

7

1391

0.50

0.13 - 0.88

Springer Spaniel

8

3906

0.20

0.06 - 0.35

Jack Russell Terrier

18

11333

0.16

0.09 - 0.23

West Highland White Terrier

3

4254

0.07

0.00 - 0.15

Border Collie

3

4501

0.07

0.00 - 0.14

Cocker Spaniel

4

6353

0.06

0.00 - 0.12

Yorkshire Terrier

2

5512

0.04

0.00 - 0.09

German Shepherd Dog

1

5993

0.02

0.00 - 0.05

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