Endoscopic ultrasonography-guided fine needle aspiration biopsy in follow-up patients with gastrointestinal stromal tumours

Objectives Since all gastrointestinal stromal tumours (GISTs) are practically considered to be potentially malignant, they must be clinically differentiated from other submucosal tumours (SMTs). In this study, we carried out endoscopic ultrasonography-guided fine needle aspiration biopsy (EUS-FNAB) against follow-up SMTs to examine whether the method is sufficient for pathological diagnosis and analysis of c-kit mutation. The relationship between tumour growth and c-kit mutation was also examined. Methods The tumour tissues were obtained by EUS-FNAB from 10 Japanese follow-up cases with SMT. Paraffin sections of tissues were used for haematoxylin and eosin staining, and for immunohistochemistry. Genomic DNA was extracted from the sections, and c-kit gene fragments of exons 9, 11, 13 and 17 were amplified by polymerase chain reaction and directly sequenced. Results Nine SMTs were diagnosed as GIST and one was diagnosed as schwannoma by immunohistochemistry. Mutation at exon 11 was detected in six of nine GISTs, but no mutations were detected at exons 9, 13 and 17 in all GISTs. The case of schwannoma did not have any mutations at exons 9, 11, 13 and 17. Statistical significance was not observed between the average growth rate of six GISTs with the mutation and that of three GISTs without the mutation (P = 0.694). Conclusions EUS-FNAB against SMTs was useful for the differential diagnosis of SMT and the analysis of c-kit mutation. The c-kit mutation might not be one of the predictable markers for rapid tumour growth.