后肾腺瘤的CT影像特征(附1例报告并文献复习)

黄剑华 麦源 钟羽翔 刘再毅 蒲小勇 徐战平

·临床研究·

后肾腺瘤的CT影像特征(附1例报告并文献复习)

黄剑华 麦源 钟羽翔 刘再毅 蒲小勇 徐战平

目的提高对后肾腺瘤的影像诊断水平。方法回顾性分析1例后肾腺瘤患者的临床资料，术前CT检查诊断为左肾嫌色细胞癌，行腹腔镜下左肾部分切除术，术后病理确诊为后肾腺瘤。结果CT提示左肾下极实性肿物，平扫期肿物边界不清，内部密度不均，稍低于邻近肾实质密度，伴有坏死灶和点状钙化，增强扫描肿块呈不均匀轻度强化，双期增强扫描呈渐进性强化，强化程度始终明显低于邻近正常肾实质。术后病理确诊为后肾腺瘤。术后患者恢复良好，随访8个月，未见肿瘤复发。结论后肾腺瘤是罕见的肾上皮源性肿瘤，其CT影像表现有一定特异性，但与其他乏血供肾肿瘤难以鉴别，特别是肾嫌色细胞癌和乳头状肾细胞癌。术前的准确诊断对选择合适的临床治疗策略十分重要，可行术前或术中的病理检查鉴别。

肾肿瘤； 后肾腺瘤； 诊断

后肾腺瘤是一种罕见的良性肾肿瘤，来源于肾上皮细胞。目前报道的后肾腺瘤不足200例[1]，少有报道描述其CT影像学特征。我们报告1例广东省人民医院收治的经病理确诊的后肾腺瘤患者，分析其CT影像表现，并结合国内外文献复习，探讨后肾腺瘤的CT影像特征，以提高对该病的诊断水平。

病例报告

患者，女，54岁，因“体检发现左肾肿物2月”于2015年12月11日入院。患者2个月前体检行彩超检查发现左肾肿物，无腰痛、腹痛、血尿等症状。既往史：否认“高血压”、“糖尿病”等病史，否认“肝炎”、“结核”等传染病史，否认食物、药物过敏史，不吸烟，不饮酒，否认家族遗传性疾病病史。入院体检：全身浅表淋巴结未触及肿大，心肺检查无异常，腹平软，肝、脾、双肾肋下未触及，全腹无压痛、反跳痛，Murphy’s征阴性，肝区、双肾区无叩击痛。双下肢无水肿。血常规、尿常规、凝血功能、肝肾功能未见异常。彩超示左肾下极稍高回声肿物，大小92 mm×42 mm，内部回声不均，考虑诊断左肾细胞癌。CT检查提示左肾下极实性肿物，大小55 mm×51 mm×92 mm，平扫肿物边界不清、外突，类圆形，肿物内部密度不均，稍低于邻近肾实质密度，有一小片低密度的坏死灶和多个高密度的点状钙化;增强扫描肿物不均匀轻度强化，在双期增强过程中呈现缓慢、持续的强化，但强化程度明显低于邻近正常肾实质，CT诊断考虑肾嫌色细胞癌(图1)。术前诊断：左肾癌。R.E.N.A.L评分为2+1+1+a+2=6a，予行腹腔镜下左肾部分切除术，手术过程顺利，切除标本可见完整、边界清楚的肿瘤，大小90 mm×60 mm×50 mm。显微镜下，肿瘤细胞丰富，大小较均匀一致，紧密排列成腺管样，伴少量嗜酸性胞质和深染的卵圆形细胞核，无明显异型性。病理诊断符合后肾腺瘤。最后诊断：左肾后肾腺瘤。术后随访8个月，未见肿瘤复发。

A、B、C：分别是横断面的平扫期、皮质期和髓质期；D、E、F：分别是矢状面的平扫期、皮质期、髓质期；G、H、I、J：为三维重建图像

图1 腹部CT检查，左肾下极前方实性肿块，大小55 mm×51 mm×92 mm，与肾实质分界欠清，平扫肿块密度不均匀，CT值约37 HU，内见小片状低密度区及数个斑点状钙化影散在分布；增强扫描肿块呈不均匀轻度强化，双期增强扫描呈渐进性强化，皮质期肿块CT值约56 HU，髓质期肿块CT值约74 HU，强化程度始终明显低于邻近正常肾实质

讨 论

后肾腺瘤约占成人肾脏上皮源性肿瘤的0.2%[2-3]，最先由Brisigotti等[4]于1992年提出并命名。2004年世界卫生组织肾脏肿瘤病理组织学分类标准中将后肾肿瘤分为后肾腺瘤、后肾纤维腺瘤、后肾间质瘤，后肾腺瘤是后肾肿瘤家族中最常发生、预后最好的类型。后肾腺瘤可发生于儿童或成人，多数发病年龄为50～60岁，男女比例约1∶2，多为单侧单病灶。后肾腺瘤生物学行为常为良性，生长缓慢，多为偶然发现，无明显临床症状[3]，实验室检查大多无异常，文献报道10%～12%的患者可能出现红细胞增多症表现[5]。虽然有个别报道其可转移至淋巴结或骨[6-9]，但后肾腺瘤被普遍认为是一种良性肿瘤，有良好预后，部分病例可行保留肾单位肾部分切除术成功切除肿瘤[1,10-11]，为该类肿瘤的首选术式。然而，由于目前报道的后肾腺瘤病例不足200例，临床工作中对其缺乏足够的理解，后肾腺瘤容易被误诊为肾恶性肿瘤，特别是最常见的肾细胞癌。为了避免由于误诊而施行不必要的根治性肾切除手术，术前正确诊断变得愈加重要。CT检查对肾肿瘤的鉴别诊断有一定帮助。

我们以“肾肿瘤，腺瘤”为检索词通过万方医学数据库对中文文献进行检索，以“Metanephric adenoma”为检索词通过PubMed数据库进行检索，检索时间截止至2016年8月，可见多篇与后肾腺瘤有关的中外文文献，多为个案报道，国外文献报道过的病例约100多例，其中儿童占20%[12]，描述后肾腺瘤的CT影像表现的文章8篇。国内文献报道不超过100例，国内单中心报道例数最多的为荆宏伟等[13]报道的11例，详细描述后肾腺瘤的CT影像表现的文章仅有1篇。马莹等[14]回顾分析5例后肾腺瘤患者，认为后肾腺瘤的CT影像特点为平扫期呈稍低或稍高密度，可见囊变及钙化，边界清楚，增强扫描呈轻中度强化，如患者为女性并伴有红细胞增多症时，应高度怀疑后肾腺瘤。国外文献报道，典型的CT影像表现为单个的圆形或卵圆形实性肿物，边界清楚，位于肾实质内，部分外突于肾轮廓外[5,15-20]。可见囊性成分、坏死灶、出血灶或钙化灶[15-17]。在CT平扫时，与邻近正常肾实质比较，后肾腺瘤可表现为稍高密度、等密度或稍低密度[16,18-19]，密度多不均匀。CT增强影像表现为密度不均匀肿物呈渐进性轻度强化[5,12]，延迟期肿物密度明显低于邻近正常肾实质[15-16]，可见肿物内部无增强区，为出血灶或坏死灶的特征表现。从CT增强表现来看，后肾腺瘤为乏血供肿瘤。本例患者的CT影像表现除了边界不清以外，符合上述后肾腺瘤的CT影像表现。Zhu等[16]报道8例后肾腺瘤患者，均表现为边界不清。因此，肿物的边界是否清楚不应作为诊断后肾腺瘤的CT影像特征。

在临床实践中，后肾腺瘤应与肾细胞癌，特别是肾透明细胞癌、嫌色细胞癌、乳头状肾细胞癌相鉴别。肾透明细胞癌是最常见的肾细胞癌，更多可能会伴有囊性、出血或坏死成分[21]，是富血供肿瘤，通过增强CT检查易于诊断，CT增强通常表现为不均匀强化，皮髓质期强化显著高于正常肾实质[22]，排泄期强化快速减退。然而，后肾腺瘤与肾嫌色细胞癌、乳头状肾细胞癌的鉴别十分困难，后二者均为乏血供肿瘤。本例CT诊断考虑为肾嫌色细胞癌，主要是因为后肾腺瘤和肾嫌色细胞癌有相同的CT强化特征，均为持续渐进的轻度强化。但肾嫌色细胞癌也有其特征性的CT表现，如极少伴有囊性、出血或坏死成分，常见为平扫时的均匀密度和增强时的均匀强化[23]，有时呈轮辐样强化[24]。然而乳头状肾细胞癌则难与后肾腺瘤相鉴别，二者同样表现为乏血供、持续渐进的轻中度强化[23]，需要通过术前细针抽吸穿刺活检或术中冷冻病理检查鉴别[25]。

对于儿童患者，后肾腺瘤需与肾母细胞瘤(Wilms瘤)相鉴别。后者的平均发病年龄为3岁，90%在6岁以内，而后肾腺瘤的中位发病年龄为48.6岁。Wilms瘤通常体积巨大，内部密度不均匀，常伴出血、坏死、脂肪或钙化[26]，常见淋巴结转移，囊性变并不少见，可为双侧发病，并可因肿瘤巨大而压迫邻近肾实质，只有9%的Wilms瘤伴有钙化，据此可鉴别二者。

总之，后肾腺瘤是罕见的良性肾脏上皮源性肿瘤。后肾腺瘤的CT影像特征缺乏特异性，使其难与其他乏血供肾肿瘤相鉴别，特别是肾嫌色细胞癌和乳头状肾细胞癌。术前的准确诊断对选择合适的临床治疗策略十分重要，可行术前或术中的病理检查鉴别。其最终诊断需依靠组织细胞学检查。

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(本文编辑：熊钰芬)

CT imaging features of metanephric adenoma: a case report and review of the literatures

HUANGJian-hua*,MAIYuan,ZHONGYu-xiang,LIUZai-yi,PUXiao-yong,XUZhan-ping.

*DepartmentofUrology,FoshanHospitalofTraditionalChineseMedicine,Foshan528000,ChinaCorrespondingauthor：XUZhan-ping,E-mail:xuzhanping2004@163.com

Objective To improve the diagnostic level of metanephric adenoma (MA). Methods Clinical data of 1 case of MA was analyzed retrospectively. The patient underwent CT examination and was diagnosed as chromophobe renal cell carcinoma, then underwent laparoscopic partial nephrectomy. The final pathological findings were in accordance with MA. Results CT confirmed the presence of a solid mass in the lower pole of the left kidney. On unenhanced CT scan the mass was poorly-defined. The density of the mass was heterogeneous and slightly lower than that of the adjacent normal renal parenchyma. The mass was characterized by a small sheet of necrotic area with low density and multiple small nodules of calcification with high density in its interior. On contrast-enhanced CT scan, the mass showed a pattern of obviously heterogeneous enhancement and during the dual-phase contrast-enhanced CT scan the enhancement was slow and prolonged. The degree of enhancement was significantly lower than that of adjacent normal renal parenchyma. The final pathological findings were in accordance with MA. The patient recovered well, and there was no recurrence after 8 months of follow-up. Conclusions MA is an extremely rare and benign renal neoplasm originating in the epithelial cells of the kidney. The CT imaging features of MA have certain specificity, but it is hard to differentiate MA from other hypovascular renal tumors, especially of chromophobe renal cell carcinoma and papillary renal cell carcinoma. Accurate diagnosis is important for selecting the most appropriate clinical treatment strategy. Preoperative or intraoperative pathological examination may be recommended for the diagnosis of MA.

Kidney neoplasms; Metanephric adenoma; Diagnosis

528000 佛山市中医院泌尿外科(黄剑华、麦源、钟羽翔、徐战平)；广东省人民医院放射科(刘再毅)；广东省人民医院泌尿外科(蒲小勇)

徐战平，E-mail:xuzhanping2004@163.com

10.3870/j.issn.1674-4624.2016.05.004

2016-09-08)