不同病理分级的胰腺神经内分泌肿瘤的MRI征象对比分析及“主胰管绕道征”的诊断价值探讨

目的:对比分析G1、G2级胰腺神经内分泌肿瘤（pNEN）的MRI征象，探讨“主胰管绕道征”的诊断价值。方法:收集32例pNEN患者的临床资料，以术后病理学检查为金标准，定量分析G1、G2级临床指标及影像学指标的差异，并着重分析pNEN与主胰管的关系。结果:32例患者中，病理分级G1、G2、G3级的患者分别有12例、16例、4例，分别以胰尾、胰头、胰颈为主要发生部位。与G1级神经内分泌瘤（NET）相比，G2级NET肿瘤直径显著增大，不规则形态的病灶增多，边缘模糊，生物学行为出现明显恶性倾向，主胰管扩张、胰腺外侵犯及淋巴结/肝转移的发生率升高。G1级NET的MRI平扫信号均质程度高于G2级（P＜0.05），但二者在增强MRI扫描的各个期象信号强度均无明显差异（P＞0.05）。28例NET患者中，22例（78.6%）出现主胰管绕道征；神经内分泌癌（NEC）患者无一例出现此征象。术前，28例NET的诊断准确率为78.6%（22/28），存在6例误诊，其中，3例误诊为胰腺癌，2例误诊为囊腺瘤（癌），1例误诊为胰腺假性囊肿。在原MRI诊断依据的基础上纳入“主胰管绕道征”，诊断准确率提高至89.3%（25/28），但仍存在3例误诊，其中2例误诊为囊腺瘤（癌），1例误诊为胰腺假性囊肿，排除了胰腺癌的误诊。结论:MRI对鉴别诊断良恶性pNEN有较高的准确性，但对部分G1与G2级NET仍存在一定的误诊率，主胰管绕道征可帮助减少出现胰腺癌误诊。

Comparative analysis of MRI signs of different grade pNEN and diagnostic value of "the bypass sign of main pancreatic duct"

Objective:To compare and analyze the MRI features of grade G1 and G2 pNEN，and to explore the diagnostic value of the bypass sign of main pancreatic duct.Methods:The clinical data of 32 patients with pNEN were retrospectively analyzed，and the difference of clinical indicators between G1 and G2 was quantitatively analyzed.Results: Among the 32 patients，there were 12 cases in G1，16 cases in G2 and 4 cases in G3，and the main sites were tail of pancreas，head of pancreas and neck of pancreas.Compared with G1 grade，G2 grade tumors had significantly larger diameter，more irregular shape lesions，blurred margins and obvious malignant tendency in biological behavior.The level of MRI plain scan signal homogenization of G1 NET was higher than that of G2（P＜0.05)，but there was no significant difference in signal intensity between the two phases of the enhanced MRI scan（P>0.05).Among 28 patients with NET，22（78.6%) had the "the bypass sign of the main pancreatic duct",and none of the NEC patients had this sign.Before operation，the accurate diagnostic rate of NET in 28 cases was 78.6%（22/28)，and 6 cases were misdiagnosed."The bypass sign of main pancreatic duct" was included on the basis of the original MRI diagnosis.The accurate diagnosis rate was increased to 89.3%（25/28)，but there were still 3 cases of misdiagnosis.Conclusion:MRI has a high accuracy in the differential diagnosis of benign and malignant pNEN，but there is a certain rate of misdiagnosis for partial G1 and G2 NET.The main duct bypass sign can help to reduce the misdiagnosis of pancreatic cancer.