胰腺导管腺癌（PDAC）是最常见的原发性胰腺恶性肿瘤，在美国癌症相关死亡率中排名第四。通常，PDAC 在图像上表现为缺乏血管的肿块，伴有上游胰管扩张和胰管突然切断、远端胰腺萎缩和血管包绕，并伴有转移性病变，包括淋巴结肿大。然而，也可能会出现限制潜在 PDAC 检测的非典型表现。非典型 PDAC 特征包括与相关病症相关的发现，例如急性或慢性胰腺炎、与实质等信号的肿块、多重性、弥漫性肿瘤浸润、相关钙化和囊性成分。几种肿瘤和炎症性疾病可以模仿 PDAC，例如十二指肠旁“沟”胰腺炎、自身免疫性胰腺炎、局灶性急性和慢性胰腺炎、神经内分泌肿瘤、实性假乳头状肿瘤、转移瘤和淋巴瘤。由于 CT 和 MRI 特征重叠，区分这些病症与 PDAC 可能具有挑战性；然而，某些发现可以帮助区分。弥散加权 MRI 可能有帮助，但也可能是非特异性的。准确的诊断对于指导 PDAC 的治疗计划和潜在结果以及避免对其中一些类似物进行活检或手术治疗至关重要。在某些情况下，诊断可能仍需要活检。作者描述了 PDAC 的典型和非典型影像学表现，以及可能有助于区分 PDAC 与其模仿者的特征。 ©RSNA，2023 本文提供在线补充材料。本文的测验问题可通过在线学习中心获得。请参阅本期 Zins 特邀评论。

Pancreatic ductal adenocarcinoma (PDAC) is the most common primary pancreatic malignancy, ranking fourth in cancer-related mortality in the United States. Typically, PDAC appears on images as a hypovascular mass with upstream pancreatic duct dilatation and abrupt duct cutoff, distal pancreatic atrophy, and vascular encasement, with metastatic involvement including lymphadenopathy. However, atypical manifestations that may limit detection of the underlying PDAC may also occur. Atypical PDAC features include findings related to associated conditions such as acute or chronic pancreatitis, a mass that is isointense to the parenchyma, multiplicity, diffuse tumor infiltration, associated calcifications, and cystic components. Several neoplastic and inflammatory conditions can mimic PDAC, such as paraduodenal "groove" pancreatitis, autoimmune pancreatitis, focal acute and chronic pancreatitis, neuroendocrine tumors, solid pseudopapillary neoplasms, metastases, and lymphoma. Differentiation of these conditions from PDAC can be challenging due to overlapping CT and MRI features; however, certain findings can help in differentiation. Diffusion-weighted MRI can be helpful but also can be nonspecific. Accurate diagnosis is pivotal for guiding therapeutic planning and potential outcomes in PDAC and avoiding biopsy or surgical treatment of some of these mimics. Biopsy may still be required for diagnosis in some cases. The authors describe the typical and atypical imaging findings of PDAC and features that may help to differentiate PDAC from its mimics. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Zins in this issue.