Nuclear expression of STAT5 in intraductal papillary mucinous neoplasms of the pancreas.

Intraductal papillary mucinous neoplasms (IPMNs) are noninvasive lesions of the pancreas and classified as intraductal papillary mucinous adenomas (IPMAs), borderline IPMNs, and intraductal papillary mucinous carcinomas (IPMCs). Expression patterns of the specific genes alter during IPMN progression. Based on the evidence that signal transducers and activators of transcription (STAT) 5 play important roles in tumor development, we tested STAT5 expression in IPMAs, borderline IPMNs, and IPMCs by immunohistochemical method. STAT5 frequently expressed in the nuclei of tumor cells of borderline IPMNs or IPMCs but was not observed in those of IPMAs. Nuclear expression of STAT5 protein correlated to the Ki-67 labeling index of the examined IPMNs. STAT5 protein could contribute to the progression and proliferation of IPMNs.