To investigate the value of certain CT features in differentiating primary retroperitoneal tumors. Methods:Seventy-nine cases with primary retroperitoneal tumors who underwent MSCT examinations proven by surgery and pathology were studied.CT features were evaluated and compared between benign and malignant groups and different tumors,including the size,growth patterns,specific lesion components,as well as the patterns of enhancement.Results:Six-ty-seven cases (84.8%)were correctly localized.Thirty-two benign (76.2%)and 35 malignant (94.6%)lesions were cor-rectly diagnosed respectively.The signs denoting malignant neoplasms included the larger size,infiltrative growth,moderate and intensive enhancement,necrosis and cystic degeneration,and calcification.The sensitivity,specificity,positive predicitive value (PPV),and negative predicitive value (NPV)of serpiginous growth pattern in diagnozing lymphangioma and neuro-genic tumors were 75.0%,98.4%,92.3% and 93.9% respectively.The prensence of fat was a quite good predicitive sign of liposarcoma and teratoma,with sensitivity,specificity,PPV,and NPV of 85.0%,98.3%,94.4% and 95.1% respectively in this study.The sensitivity,specificity,PPV,and NPV of water density within the mass in diagnosing lymphangioma and ter-atoma were 80.0%,93.2%,80.0%,93.2% respectively.Complete cystic lesions were highly suggestive of lymphangioma, with the sensitivity,specificity,PPV,and NPV of 100%,98.6%,90.0% and 100%.Calcification is relatively sensitive for neurogenic tumors and teratomas,with the sensitivity,specificity,PPV and NPV of 51.2%,87.5%,80.0%,64.8% respec-tively.Extreme hypervascularity was sensitive to the diagnosis of paraganglioma,with the sensitivity,specificity,PPV and NPV of 77.8%,98.6%,87.5% and 97.2% respectively.Conclusion:Carefully analyzing CT features can be helpful to dif-ferentiate between benign and maligant retroperitoneal tumors.Certain characteristics can lead to a correct diagnosis of cer-tain tumors.%_目的：探讨特定 CT 征象对原发性腹膜后肿瘤（简称腹膜后肿瘤）鉴别诊断的价值。方法：回顾性分析经手术病理证实的79例腹膜后肿瘤的 MSCT 资料，确定对良恶性肿瘤鉴别有价值的征象，探讨生长方式、内部结构特点及增强表现对特定类型肿瘤的诊断价值。结果：67例（84．8％）定位诊断正确。32例（76．2％，32/42）良性肿瘤及35例（94．6％，35/37）恶性肿瘤定性诊断正确，提示恶性肿瘤有价值的征象包括病灶体积较大、浸润性生长、中重度强化、坏死、囊变及钙化。匍匐状生长对诊断淋巴管瘤及神经源性肿瘤的敏感度、特异度、阳性预测值（PPV）及阴性预测值（NPV）分别为75．0％、98．4％、92．3％、93．9％。脂肪密度对诊断脂肪肉瘤与畸胎瘤的敏感度、特异度、PPV 及 NPV 分别为85．0％、98．3％、94．4％、95．1％。水样密度对诊断淋巴管瘤与畸胎瘤的敏感度、特异度、PPV 及 NPV 分别为80．0％、93．2％、80．0％、93．2％。囊肿样表现对诊断淋巴管囊肿的敏感度、特异度、PPV 及 NPV 分别为100％、98．6％、90．0％、100％。钙化对诊断神经源性肿瘤及畸胎瘤的敏感度、特异度、PPV 及 NPV 分别为51．2％、87．5％、80．0％、64．8％。强化程度接近血管对诊断副神经节瘤的敏感度、特异度、PPV 及 NPV 分别为77．8％、98．6％、87．5％、97．2％。结论：CT 征象分析有助于腹膜后良恶性肿瘤的鉴别及特定肿瘤的诊断。
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