The usefulness of lymphoid enhancer‐binding factor 1 and androgen receptor in diagnosing solid pseudopapillary neoplasm of the pancreas on cytopathology

Unraveling the enigma: A comprehensive review of solid pseudopapillary tumor of the pancreas

Solid pseudopapillary tumor of the pancreas (SPTP) is a rare neoplasm predominantly observed in young females. Pathologically, CTNNB1 mutations, β-catenin nuclear accumulation, and subsequent Wnt-signaling pathway activation are the leading molecular features. Accurate preoperative diagnosis often relies on imaging techniques and endoscopic biopsies. Surgical resection remains the mainstay treatment. Risk models, such as the Fudan Prognostic Index, show promise as predictive tools for assessing the prognosis of SPTP. Establishing three types of metachronous liver metastasis can be beneficial in tailoring individualized treatment and follow-up strategies. Despite advancements, challenges persist in understanding its etiology, establishing standardized treatments for unresectable or metastatic diseases, and developing a widely recognized grading system. This comprehensive review aims to elucidate the enigma by consolidating current knowledge on the epidemiology, clinical presentation, pathology, molecular characteristics, diagnostic methods, treatment options, and prognostic factors.

A limited panel of INSM1 and LEF1 immunostains accurately distinguishes between pancreatic neuroendocrine tumor and solid pseudopapillary neoplasm

Solid pseudopapillary neoplasm (SPN) and well differentiated pancreatic neuroendocrine tumor (PNET) can show significant cytomorphological overlap. In this study, we evaluated the role of INSM1 and LEF1 immunohistochemical stains in distinguishing between these two tumors. 22 SPN and 25 PNET surgically resected cases were stained for both INSM1 and LEF1. All the 22 cases of SPN showed strong and diffuse nuclear staining for LEF1 (in >95 % of tumor cells), while all 25 PNET were negative for LEF1. All 25 PNET cases were positive for INSM1 (moderate to strong intensity nuclear staining in >50 % of the tumor cells), while all 22 cases of SPN were negative for INSM1. The results of our study show that a limited panel comprising of INSM1 and LEF1 immunostains accurately distinguishes between SPN and PNET.

[Diagnostic Utility of LEF1 Immunostain in Cytology Specimens of Solid Pseudopapillary Neoplasm of Pancreas]

Solid pseudopapillary neoplasm (SPN) of the pancreas is a rare neoplasm. Diagnosis of SPN requires an integrated approach with aid of radiology, biopsy, cytology, and immunohistochemical stains. Although morphological features in combination with nuclear positivity of β-catenin IHC have been the gold standard of SPN diagnosis, but overlapping morphology and immunohistochemical findings with other entities in differential diagnoses such as pancreatic neuroendocrine tumors and pancreatic ductal adenocarcinoma make the diagnosis of SPN difficult particularly in limited cytology specimens. Lymphoid enhancer-binding factor 1 (LEF1), a key player in the Wnt signaling pathway, has shown promising diagnostic utility in SPN in recent literatures.

METHODS

In this retrospective study, we evaluated the diagnostic utility of LEF1 IHC in SPN in cytology specimens. LEF1 IHC was performed and compared with β-catenin, synaptophysin, and chromogranin immunostains in 13 SPN and 23 pancreatic neuroendocrine tumors (PanNETs) cytology cases with retrievable cell blocks.

RESULTS

LEF1 was positive in 13 of 13 (100%) SPNs and was negative in all PanNETs (0%).

CONCLUSION

LEF1 shows 100% sensitivity and specificity in cytology specimens for SPN and can be valuable immuno-stain in the diagnosis of SPN in cytology cell blocks.

Acinar cell induced autolysis is a frequent occurrence in CytoLyt-fixed pancreatic fine needle aspiration specimens: An analysis of 157 cytology samples

BACKGROUND

Although 10% formalin is a standard preservative in pancreatic FNAs, the effect of CytoLyt on pancreatic tissue preservation has not been systematically explored.

METHODS

Smears and cell blocks from CytoLyt-fixed (CF-CBs) and formalin-fixed (FF-CBs) pancreatic FNAs were blindly reviewed without knowledge of the fixative used, and the presence of tissue/tumor autolysis was noted. Controls included FF-CBs from pancreatic FNAs, CF-CBs from nonpancreatic FNAs, and 4 pancreatic FNAs with matched CF-CBs and FF-CBs.

RESULTS

We found that 62 of 85 (73%) pancreatic FNAs with CF-CBs showed significant autolysis, which was most pronounced in acinar cells and/or tumor cells with benign acinar cells in the background, compared with 2 of 46 (4%) FF-CBs (P < .0001) and 3 of 26 (12%) CF-CBs from nonpancreatic FNAs (73% vs 12%; P < .0001). Of the 4 pancreatic FNAs with matched CF-CBs and FF-CBs, all 4 CF-CBs showed marked autolysis versus none of the matched FF-CBs. Of the 23 (27%) pancreatic FNAs with CF-CBs that did not show autolysis, 10 had no acinar cells, and 7 had only minute tissue fragments on CB.

CONCLUSION

While CytoLyt is a useful fixative for nonpancreatic FNAs it is a suboptimal fixative for pancreatic FNAs and is associated with tissue/tumor autolysis in the majority of cases, influencing morphologic evaluation, and potentially immunocytochemical staining. Autolysis appears to be due to acinar enzymes whose effect is likely interrupted/inhibited by formalin fixation. Cytopathologists and cytotechnologists should be mindful of this pitfall and should avoid using CytoLyt as a fixative for pancreatic FNAs.

Fine needle aspiration cytology with the aid of immunocytochemistry on cell-block confirms the diagnosis of solid pseudopapillary neoplasm of the pancreas

INTRODUCTION

To determine the diagnostic efficacy of fine needle aspiration cytology (FNAC) in cases of pancreatic solid pseudopapillary neoplasm (PSPN) with emphasis on the cytomorphological features and to evaluate the contribution of immunocytochemistry on FNAC cell-block (CB) in cases of PSPN.

METHODS

It is a retrospective study in which ultrasound-guided FNAC of pancreatic lesions diagnosed as PSPN between years 2009 and July 2019 were reviewed along with cytohistological correlation. Immunocytochemistry on CB was performed, wherever required.

RESULTS

A total of 16 patients with a cytological diagnosis of PSPN of the pancreas were identified. The most common cytological findings were characteristic branching pseudopapillary fragments with central thin, delicate capillaries associated with the amorphous myxoid substance, surrounded by tumour cells with mild pleomorphism. Immunocytochemistry was performed on CB of six cases. The tumour cells revealed nucleocytoplasmic positivity for β-catenin, cytoplasmic positivity for vimentin, membranocytoplasmic positivity for CD10 and nuclear positivity for progesterone receptor in all the cases, while they were negative for chromogranin, CD56, pan-cytokeratin and epithelial membrane antigen. The resected histopathological specimen was available in 10cases, and all were confirmed as PSPN.

CONCLUSION

Although PSPN has a characteristic cytomorphology, cell-block immunocytochemistry on FNA material confirms the diagnosis in problematic cases and excludes other pancreatic tumours, thus helping in appropriate management.