Pancreatic neuroendocrine tumors (PanNETs) are rare neoplasms that include even rarer variants that may pose different diagnostic problems, especially in fine needle aspiration cytology (FNAC). We describe the diagnostic clues of the amyloid-rich variant of PanNETs in endoscopic ultrasound (EUS)-guided fine needle aspiration cytology (EUS-FNAC). Three cases of PanNETs with an amyloid-rich stromal component were retrieved and retrospectively reviewed. For every case, the pancreatic lesion was investigated by a EUS-FNAC procedure. The final diagnosis was supported by immunocytochemistry and Congo red staining. All cases had similar EUS-FNAC features: neoplastic cells were entrapped in an eosinophilic, homogeneous dense and amorphous matrix. The neuroendocrine nature was confirmed by immunoexpression of synaptophysin and chromogranin A, while the amorphous stroma was characterized as amyloid based on positive Congo red staining. Regarding the hormonal profile, no insulin or proinsulin reactivity was observed, but all cases were diffusely positive for amylin. The diagnosis of uncommon variants of PanNETs, such as the amyloid-rich, is challenging especially in EUS-FNAC procedures because of a unique and misleading morphology, potentially mimicking fibrotic conditions and amyloid deposition within systemic amyloidosis. In cytology specimens, the presence of amorphous material requires amyloid deposition to be considered in the differential diagnosis of pancreatic neoplasms with neuroendocrine phenotype.

中文翻译：

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富含淀粉样蛋白的胰腺神经内分泌肿瘤：内窥镜超声引导细针穿刺细胞学 (EUS-FNAC) 中的潜在诊断缺陷。

胰腺神经内分泌肿瘤 (PanNETs) 是罕见的肿瘤，包括更罕见的变异，可能会造成不同的诊断问题，尤其是细针穿刺细胞学 (FNAC)。我们描述了内窥镜超声 (EUS) 引导的细针抽吸细胞学 (EUS-FNAC) 中富含淀粉样蛋白的 PanNETs 变体的诊断线索。检索并回顾性审查了三例具有富含淀粉样蛋白的基质成分的 PanNET。对于每个病例，通过 EUS-FNAC 程序调查胰腺病变。最终诊断得到免疫细胞化学和刚果红染色的支持。所有病例都具有相似的 EUS-FNAC 特征：肿瘤细胞被包裹在嗜酸性、均匀致密和无定形的基质中。突触素和嗜铬粒蛋白 A 的免疫表达证实了神经内分泌的性质，而无定形基质的特征是基于阳性刚果红染色的淀粉样蛋白。关于激素谱，未观察到胰岛素或胰岛素原反应性，但所有病例均呈弥漫性胰淀素阳性。PanNETs 的罕见变体（例如富含淀粉样蛋白）的诊断具有挑战性，尤其是在 EUS-FNAC 程序中，因为其独特且具有误导性的形态，可能模仿系统性淀粉样变性中的纤维化状况和淀粉样蛋白沉积。在细胞学标本中，无定形物质的存在需要在鉴别诊断具有神经内分泌表型的胰腺肿瘤时考虑淀粉样蛋白沉积。但所有病例对胰淀素呈弥漫性阳性。PanNETs 的罕见变体（例如富含淀粉样蛋白）的诊断具有挑战性，尤其是在 EUS-FNAC 程序中，因为其独特且具有误导性的形态，可能模仿系统性淀粉样变性中的纤维化状况和淀粉样蛋白沉积。在细胞学标本中，无定形物质的存在需要在鉴别诊断具有神经内分泌表型的胰腺肿瘤时考虑淀粉样蛋白沉积。但所有病例对胰淀素呈弥漫性阳性。PanNETs 的罕见变体（例如富含淀粉样蛋白）的诊断具有挑战性，尤其是在 EUS-FNAC 程序中，因为其独特且具有误导性的形态，可能模仿系统性淀粉样变性中的纤维化状况和淀粉样蛋白沉积。在细胞学标本中，无定形物质的存在需要在鉴别诊断具有神经内分泌表型的胰腺肿瘤时考虑淀粉样蛋白沉积。