Is Endoscopic Ultrasound-Fine Needle Aspiration for Ki67 Aspirational Enough?

Pancreatic neuroendocrine tumors (PNETs) are relatively rare with an estimated incidence of 2.2 cases per 1,000,000 in the US, of which 60%–90% are classified as non-functional. PNETs have deleterious effects such as hormone secretion (functional), metastases, or mass effects. Surgical resection is recommended for non-metastatic primary tumors that produce hormones, compress adjacent structures, or are >2 cm. However, due to frequent abdominal imaging, there has been a corresponding increase in the detection of small asymptomatic PNETs. Defining the optimum management strategy for these incidentally found non-functional PNETs is challenging due to their heterogeneous behavior. There is an elevated risk of metastasis and mortality if high-risk lesions are not resected. Conversely, while most small PNETs are amenable to enucleation/local resection, others may require invasive procedures such as a pancreaticoduodenectomy or distal pancreatectomy with splenectomy. The potential morbidity associated with these procedures must be carefully considered in the case of low-grade lesions which are likely to have an indolent course. Therefore, appropriate pre-operative risk-stratification of these lesions is challenging. Ki67 as a measure of proliferation rate has been found to be a strong prognostic indicator and is recommended by major society guidelines in conjunction with the mitotic index to adequately grade PNET lesions. The North American Neuroendocrine Tumor Society recommends that although needle biopsy or surgical resection specimens are optimal, fine needle aspiration (FNA) samples can provide adequate information in most cases. However, till date, the concordance rates of samples obtained by endoscopic ultrasound (EUS)-FNA and subsequent resected surgical specimens have been variable, ranging from 61%–84% in different studies. In this single center retrospective study titled “The Role of Endoscopic Ultrasound-Guided Ki67 in The Management of Non-Functioning Pancreatic Neuroendocrine Tumors”, Cui et al. found a 73% concordance rate between EUS-FNA cytology and surgical pathology in 37 samples. Concordance was highest for high-grade and low-grade lesions with positive predictive values of 100% and 80%, respectively. However, this study demonstrates the limitation of EUS-FNA for intermediate-grade lesions with a positive predictive value of only 37%. The authors appropriately acknowledge this limitation and further analyze the discordant specimens to identify features which would aid in the risk stratification of these lesions. Reassuringly, a majority of the lesions that were graded as intermediate-grade in EUS-FNA were downgraded after evaluation of the surgical specimen. The lone specimen that was upgraded from intermediate to high and 5 specimens that Received: February 13, 2020 Accepted: February 20, 2020 Correspondence: Yakira David Henry D. Janowitz Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, New York, NY 10029, USA Tel: +1-917-995-5408, Fax: +1-254-233-8873, E-mail: yakira.david@mountsinai. org ORCID: https://orcid.org/0000-0001-7232-0757