Well circumscribed + hyalinized stroma + Microcystic and trabecular pattern + relatively bland cytology=would consider neuroendocrine tumor first. Other consideration would include: solid and pseudopapilary tumor, and less likely microcystic serous adenoma or acinar cell carcinoma.  IHC will be helpful in this case. Thanks and I look forward to hearing the final answer.   

 难看。囊性，与周围胰腺组织界清，腺管网状结构，未见明显粘液，前几张图片暗一些，不知有无粘液？暂时考虑低恶肿瘤。不象实性假乳头状肿瘤，不象一般外分泌腺浆液性囊腺瘤或癌。