Cytopathology of solid pancreatic neoplasms: An algorithmic approach to diagnosis

Abstract

The classification and management of solid pancreatic neoplasms has expanded significantly in recent years because of advances in immunohistochemical markers, molecular diagnostics, and therapeutics. Solid pancreatic masses are subdivided into 1) ill-defined, scirrhous, and stroma-rich (ductal adenocarcinoma) and 2) well circumscribed, cellular, and stroma-poor (including neuroendocrine neoplasms, acinar cell carcinoma, pancreatoblastoma, and solid-pseudopapillary neoplasm). Definitive diagnosis, particularly of stroma-poor, circumscribed tumors, requires the incorporation of radiologic and cytologic findings, along with the judicious use of (broad, but limited) immunohistochemical panels (pancytokeratin and neuroendocrine [synaptophysin], acinar [trypsin], and solid-pseudopapillary neoplasm [β-catenin] markers), along with unstained slides. Depending on the initial results, immunohistochemical panels should be expanded to include more confirmatory (acinar and neuroendocrine) markers. This ensures that adequate material is available for definitive diagnosis/subclassification and, in some cases, grading, and/or molecular studies, particularly of grade 3 neuroendocrine neoplasms and mixed-lineage tumors. The objective of this review is to expand the understanding of the cytomorphology of solid pancreatic neoplasms using an integrated, multidisciplinary approach in their diagnosis. Knowledge and understanding of recent updates in the classification of solid pancreatic neoplasms ensures that cytopathologists appropriately triage specimens, judiciously use and interpret ancillary studies, and incorporate these results in reporting.

Cytomorphologic, immunophenotypical and molecular features of pancreatic acinar cell carcinoma

“…Pancreatic acinar cell carcinoma only accounts for 1% to 2% pancreatic malignancies and often relies on cytology specimen to establish the diagnosis. 1,4,17,24 Pancreatic acinar cell carcinoma demonstrate cytomorphological overlap with other pancreatic malignancy including PDAC and PanNET, making it one of most commonly misdiagnosed pancreatic cytology entities. 11,12,24 In current series, 2 of 8 (25%) cases had minor cytohistologic discordance.…”

“…1,4,17,24 Pancreatic acinar cell carcinoma demonstrate cytomorphological overlap with other pancreatic malignancy including PDAC and PanNET, making it one of most commonly misdiagnosed pancreatic cytology entities. 11,12,24 In current series, 2 of 8 (25%) cases had minor cytohistologic discordance. Further characterization of cytomorphological features of PACC is in need.…”

“…Pure PACC typically is with mildly increased N/C ratio. 19,24 Besides features seen in pure PACC, PACC with neuroendocrine differentiation also showed neuroendocrine tumor characteristics such as coarsely granular or speckled chromatin. Uniform population of mostly dyscohesive smear pattern can be observed.…”

Ectopic adrenal cortical tissue presenting as gastrohepatic ligament “lymph node” diagnosed by fine‐needle aspiration: A case report

“…These cells can rupture, resulting in naked nuclei and microvesicles in the background, morphologically resembling the cytoplasm of adrenal cortical tissue. 24 However, nuclei of neuroendocrine tumors often have the stippled "salt and pepper" chromatin as well as occasional endocrine HO and POLICARPIO-NICOLAS atypia. IHC will be helpful because the cells of lipid-rich neuroendocrine tumors will be negative for SF1, inhibin and A103 and positive for synaptophysin and chromogranin, and other neuroendocrine markers.…”

“…Metastatic lipid‐rich neuroendocrine tumors are characterized cytologically as having foamy, stippled to vacuolated cytoplasm. These cells can rupture, resulting in naked nuclei and microvesicles in the background, morphologically resembling the cytoplasm of adrenal cortical tissue 24 . However, nuclei of neuroendocrine tumors often have the stippled “salt and pepper” chromatin as well as occasional endocrine atypia.…”