Analysis of c-KIT exon 11 mutations in canine gastrointestinal stromal tumours.

The aim of this study was to determine the type and frequency of c-KIT exon 11 mutations in canine gastrointestinal stromal tumours (GISTs) and investigate the association between the c-KIT mutation status and KIT immunohistochemical staining pattern. Mutations in exon 11 of c-KIT were examined in 46 formalin-fixed paraffin-embedded canine GISTs using PCR of genomic DNA and reverse transcription-PCR (RT-PCR) of cDNA. Exon 11 c-KIT mutations were detected in 15/46 (32.6%) cases by conventional PCR and 34/46 (73.9%) cases by RT-PCR; the mutation detection rate was significantly higher for RT-PCR (P = 0.004, Fisher's exact test). Ten different mutations, including deletion, internal tandem duplication and point mutations, were identified by RT-PCR. Immunohistochemistry was performed using an anti-KIT antibody; diffuse KIT staining was detected in the tumour cell cytoplasm in 32/46 (69.6%) cases and partial or stippled cytoplasmic staining of KIT was observed in 14/46 (30.4%) cases. Neither pattern was significantly associated with c-KIT exon 11 mutation status (P = 1.000, chi-square test). These data indicate that c-KIT exon 11 mutations occur frequently in canine GISTs, similar to human GISTs; however, there is no association between c-KIT mutations and the KIT expression pattern in canine GISTs. This study suggests that RT-PCR is more sensitive than conventional PCR for the detection of c-KIT mutations in canine GISTs.