Grading of EUS-FNA cytologic specimens from patients with pancreatic neuroendocrine neoplasms: it is time move to tissue core biopsy?
Pancreatic neuroendocrine neoplasms (p-NENs) are rare and characterized by an indolent course, with a much better prognosis than non-neuroendocrine tumors of the pancreas. In the nonfunctional class of p-NENS, surgery remains the only curative treatment for early localized disease, but there are few therapeutic options for advanced disease. The prognosis of non-functional p-NENs is determined by many clinical criteria. In 2010, however, the World Health Organization (WHO) introduced a grading system in which determination of the Ki-67 proliferative index has become essential with key role in determining therapeutic decision in both advanced and early diseases. Conventionally, Ki-67 has been assessed on surgical specimens. In last decade, however, the availability of EUS-guided fine needle aspiration (EUS-FNA) has provided the opportunity to sample pancreatic lesions and to assess the value of this parameter pre-operatively. The few studies reporting the use of EUS-FNA cytological specimens for Ki-67 measurement showed promising results. As shown by Weynand and colleagues FNA-cytology may underestimate the staging and caution in using this method to classify tumors as low-grade (G1) should be adopted. Thus, Ki-67 expression on cytological specimens remains unsatisfactory and the need for tissue biopsy specimens has been strongly advocated. Based on a recent study that has reported a high concordance of EUS-guided core biopsy for histologic examination and surgical specimens, especially when a cut-off of 5% is used to differentiate G1 and G2 tumors, EUS tissue acquisition by core biopsy is ready for prime time and should be adopted as a standard of practice.