AIM: To evaluate the efficacy of endoscopic ultrasonography-guided fine needle aspiration(EUS-FNA) for grading pancreatic neuroendocrine tumors(PNETs).METHODS: A total of 22 patients were diagnosed with PNET by EUS-FNA between October 2001 and December 2013 at Fukushima Medical University Hospital.Among these cases,we targeted 10 PNET patients who were evaluated according to the World Health Organization(WHO) 2010 classification.Surgery was performed in eight patients,and chemotherapy was performed in two patients due to multiple liver metastases.Specimens obtained by EUS-FNA were first stained with hematoxylin and eosin and then stained with chromogranin,synaptophysin,CD56,and Ki-67.The specimens were graded by the Ki-67 index according to the WHO 2010 classification.Specimens obtained by surgery were graded by the Ki-67 indexand mitotic count(WHO 2010 classification).For the eight specimens obtained by EUS-FNA,the Ki-67 index results were compared with those obtained by surgery.In the two cases treated with chemotherapy,the effects and prognoses were evaluated.RESULTS: The sampling rate for histological diagnosis by EUS-FNA was 100%.No adverse effects were observed.The concordance rate between specimens obtained by EUS-FNA and surgery was 87.5%(7/8).Fo r t h e t w o c a s e s t re a t e d w i t h c h e m o t h e ra p y,case 1 received somatostatin analog therapy and transcatheter arterial infusion(TAI) targeting multiple liver metastases.Subsequent treatment consisted of everolimus.During chemotherapy,the primary tumor remained unconfirmed,although the multiple liver metastases diminished dramatically.Case 2 was classified as neuroendocrine carcinoma(NEC) according to the Ki-67 index of a specimen obtained by EUS-FNA; therefore,cisplatin and irinotecan therapy was started.However,severe adverse effects,including renal failure and diarrhea,were observed,and the therapy regimen was changed to cisplatin and etoposide.TAI targeting multiple liver metastases was performed.Although the liver metastases diminished,the primary tumor remained unconfirmed.These chemotherapy regimens had immediate effects for both unresectable neuroendocrine tumor(NET) and NEC cases.These two subjects are still alive.CONCLUSION: EUS-FNA was effective for PNET diagnosis and Ki-67 index grading for WHO 2010 classification,enabling informed decisions on unresectable PNET treatment by identifying NET or NEC. AIM: To evaluate the efficacy of endoscopic ultrasonography-guided fine needle aspiration (EUS-FNA) for grading pancreatic neuroendocrine tumors (PNETs). METHODS: A total of 22 patients were diagnosed with PNET by EUS-FNA between October 2001 and December 2013 at Fukushima Medical University Hospital. Amnong these cases, we targeted 10 PNET patients who were evaluated according to the World Health Organization (WHO) 2010 classification. Surgery was performed in eight patients, and chemotherapy was performed in two patients due to multiple liver metastases. obtained by EUS-FNA were first stained with hematoxylin and eosin and then stained with chromogranin, synaptophysin, CD56, and Ki-67. The specimens were graded by the Ki-67 index according to the WHO 2010 classification. Specimens obtained by surgery were graded For the eight specimens obtained by EUS-FNA, the Ki-67 index results were compared with those obtained by surgery. In th The two cases treated with chemotherapy, the effects and prognoses were evaluated .RESULTS: The sampling rate for histological diagnosis by EUS-FNA was 100% .No an adverse effects were observed. The concordance rate between specimens obtained by EUS-FNA and surgery was 87.5 % (7/8) .Fo rthetwocasest reted with chemothe ra py, case 1 received somatostatin analog therapy and transcatheter arterial infusion (TAI) targeting multiple liver metastases. Subsequent treatment consisted of everolimus. Drawing chemotherapy, the primary tumor remained unconfirmed, although the multiple liver metastases diminished dramatically. Case 2 was classified as neuroendocrine carcinoma (NEC) according to the Ki-67 index of a specimen obtained by EUS-FNA; therefore, cisplatin and irinotecan therapy was started. However, severe adverse effects, including renal failure and diarrhea, were observed, and the therapy regimen was changed to cisplatin and etoposide. TAI targeting multiple liver metastases was performed.Although the liver metastases diminished, the primary tumor remained unconfirmed.These regimen regimens had immediate effects for both unresectable neuroendocrine tumors (NET) and NEC cases. these two subjects are still alive. CONCLUSION: EUS-FNA was effective for PNET diagnosis and Ki-67 index grading for WHO 2010 classification, enabling informed decisions on unresectable PNET treatment by identifying NET or NEC.