Diagnostic findings of ultrasound-guided fine-needle aspiration cytology for gastrointestinal stromal tumors: proposal of a combined cytology with newly defined features and histology diagnosis.

Recently, endoscopic ultrasonography-guided fine needle aspiration (EUS-FNA) has been applied for diagnosis of gastrointestinal submucosal tumors. There have been no definite criteria, however, for the adequate cytological diagnosis of gastrointestinal stromal tumor (GIST) in practice. To facilitate this a novel method is proposed that combines cytology and histology. For 49 cases of submucosal tumor of gastrointestinal tract, EUS-FNA was performed. The aspirated materials were processed for cytology and histology. Both cytological and histological findings were examined on immunocytochemical and immunohistochemical staining of c-kit. Of 49 cases, 40 (81.6%) proved adequate for cytological and/or histological examination. On cytology, cluster types were classified into type A (piled clusters with high cellularity showing a fascicular pattern), type B (thin layered clusters with high cellularity showing a fascicular pattern), and type C (mono-layered clusters or scattered cells). Types A and B were strongly associated with histological diagnosis of GIST. Type C clusters needed confirmation on c-kit positivity and histology. Thus, the combined cytology with newly defined features, and classification and histological diagnostic method for EUS-FNA materials can contribute to improved routine diagnosis for GIST.