Differential diagnosis between pancreatic neuroendocrine and solid pseudopapillary neoplasms on endoscopic ultrasound-guided fine-needle aspiration. An immunohistochemical study

Pancreatic neuroendocrine neoplasms: Clinicopathological features and pathological staging

The nomenclature and classification of pancreatic neuroendocrine neoplasms has evolved in the last 15 years based on the advances in knowledge of the genomics, clinical behaviour and response to therapies. The current 2019 World Health Organization classification of pancreatic neuroendocrine neoplasms categorises them into three groups; pancreatic neuroendocrine tumours (PanNETs)(grade 1 grade 2, grade 3), pancreatic neuroendocrine carcinomas and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) based on the mitotic rate, Ki-67 index, morphological differentiation and/or co-existing tissue subtype. PanNETs are also classified into non-functional NET, insulinoma, gastrinoma, VIPoma, glucagonoma, somatostatinoma, ACTH-producing NET and serotonin producing NET based on hormone production and clinical manifestations. A portion of the cases were associated with genetic syndromes such as multiple neuroendocrine neoplasia 1 (MEN 1), neurofibromatosis and Von Hippel-Lindau syndrome. In view of the distinctive pathology and clinical behaviour of PanNENs, the current 8th AJCC/UICC staging system has separated prognostic staging grouping for PanNETs from the pancreatic neuroendocrine carcinomas or MiNENs. Pancreatic neuroendocrine carcinomas and MiNENs are staged according to the prognostic stage grouping for exocrine pancreatic carcinoma. The new stage grouping of PanNETs was validated to have survival curves separated between different prognostic groups. This refined histological and staging would lead to appropriate selections of treatment strategies for the patients with pancreatic neuroendocrine neoplasms.

Immunocytochemistry for SOX-11 and TFE3 as diagnostic markers for solid pseudopapillary neoplasms of the pancreas in FNA biopsies

BACKGROUND

Solid pseudopapillary neoplasms (SPNs) of the pancreas are rare malignant tumors that can be sampled via endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). Although diagnosing SPNs can be straightforward in cases with a classic morphology and a typical immunoprofile, challenges can occur with morphologic variants or limited specimens. Recently, 2 immunohistochemical stains, SRY-related high-mobility group box 11 (SOX-11) and transcription factor E3 (TFE3), have been demonstrated to be highly sensitive and specific for SPNs in pancreatic resection specimens. The current study evaluates the diagnostic utility of these stains with EUS-FNA.

METHODS

Thirteen EUS-FNA specimens from SPNs with sufficient material for immunocytochemistry were identified from 2000 to 2016. These cases were compared with 13 EUS-FNA specimens of non-SPN pancreatic neoplasms. Immunocytochemistry for SOX-11, TFE3, and β-catenin was performed on all cell blocks and then was scored independently by 2 pathologists in a masked manner.

RESULTS

Nuclear reactivity for SOX-11 was detected in 13 of 13 SPNs and in 0 of 13 non-SPNs; this resulted in sensitivity and specificity values of 100%, a positive predictive value (PPV) of 1, and a negative predictive value (NPV) of 1. Nuclear reactivity for TFE3 was detected in 9 of 13 SPNs and in 0 of 13 non-SPNs; this resulted in a sensitivity of 69.2%, a specificity of 100%, a PPV of 1, and an NPV of 0.765. Nuclear reactivity for β-catenin was detected in 13 of 13 SPNs and in 1 of 13 non-SPNs; this resulted in a sensitivity of 100%, a specificity of 92.3%, a PPV of 0.929, and an NPV of 1.

CONCLUSIONS

SOX-11 is a sensitive and specific immunocytochemical stain for SPNs in EUS-FNA specimens, and it may be useful as a diagnostic marker for distinguishing SPNs from its cytologic mimics. Cancer Cytopathol 2017;125:831-7. © 2017 American Cancer Society.