Introduction

Mast cell tumor (MCT) is the most common skin tumor affecting dogs, therefore improved diagnosis and prognosis of MCTs is crucial. Approximately 20% of MCTs are positive for a c-kit mutation. Such tumors exhibit more aggressive behavior, but on the other hand can be specifically targeted by tyrosine kinase inhibitors. Detection of the mutation currently requires testing on tissue samples. Detection of c-kit gene and mutation in liquid biopsies would provide a less invasive technique for diagnostic, therapeutic and prognostic purposes.

Objectives

Evaluate blood and urine from dogs with MCTs to detect c-kit and its internal tandem duplication mutation in exon 11 compared to control dogs.

Methods

Cutaneous MCTs were removed and blood and urine were collected from eleven dogs; liquid biopsies were also collected from five healthy, control dogs. Qiagen QIAamp® kits were used to extract DNA from tissue samples and liquid biopsies, and gel-based PCR was completed for detection of c-kit mutation.

Results

c-kit gene was detected in all biopsy samples. It was also detected in the plasma of all dogs, including the control group, and in urine of 80% of the dogs with MCTs. Two of the eleven dogs with MCTs were positive for the mutation in biopsy samples, but c-kit mutation in the corresponding liquid biopsies was not detected.

Conclusions

The detection of circulating c-kit gene in plasma was successful; however, with the methods used in this study, it was not beneficial for diagnosis. Detection of the mutation in liquid biopsies was not accomplished.