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ECR 2019 / C-3355
Renal tumor invading the inferior vena cava - almost, but not exclusively malignant
Congress: ECR 2019
Poster No.: C-3355
Type: Educational Exhibit
Keywords: Veins / Vena cava, Kidney, Abdomen, CT, MR, Catheter venography, Diagnostic procedure, Complications, Surgery, Haemorrhage, Cancer, Education and training
Authors: M.-C. Craciunoiu1, C. Caraiani2, N. Crisan1, A. Tamas-Szora1; 1Cluj-Napoca/RO, 2Cluj Napoca/RO

Findings and procedure details


Aggressive angiomiolipoma


    At times, AMLs may show extension into venous structures (renal vein and IVC). The first case of aggressive AML was reported by Kutcher et al in 1982. Between 1982 and 2013 approximately 43 similar cases were reported [10]. Imaging not only helps in tumor diagnosis, but also in preoperative assessment.


Case 1


    A 58-year-old female patient was addressed to the urology department accusing flank pain and hematuria. No relevant medical history. Abdominal US showed a well defined, hyperechoic mass in the right kidney, with extension into renal vein and IVC and absence of intratumoral blood flow, presumably an AML Fig. 8. Afterwards CT confirmed the fat content of the tumor (mean= -80HU on native CT) Fig. 9. Abdominal MRI revealed macroscopic fatty mass in the cortical and renal pelvis with extension into the venous system Fig.10. Based on the above findings, a diagnosis of aggressive AML was suggested. The pacient underwent radical right nephrectomy with thrombectomy and the histopathological examination confirmed the diagnosis.


    There are similar cases described in the literature, like the one that follows:


Case 2


    A 40-year-old female presented with mild pain, stiffness in the right flank and  dysuria. No relevant medical history. US of the abdomen showed an hyperechogenic mass in the right kidney which extended into the IVC (Fig. 11). Abdominal CT showed focal fat attenuation (-48 HU to -80 HU) in the right renal pelvis, extending into renal vein and IVC and no calcification (Fig. 12). MRI of the abdomen revealed mass in the renal pelvis appearing hyperintense on T1 and T2 weighted images and showed suppression on fat saturated images. The mass  extended into the right renal vein and IVC (Fig. 13). No hydronephrosis, locoregional lymphadenopathy or soft-tissue component was seen within the mass. Based on the above findings, a diagnosis of aggressive AML was made and confirmed by the histopathological examination [11].


    The presence of fat within a renal lesion is highly suggestive of AML; fat–containing tumors on US, CT or MRI invading renal vein and IVC should raise suspicion of an AML with aggressive behaviour. Differentials of such fatty mass include fat-containing RCC, liposarcoma and Wilms tumor [6].



Fat-containing renal cell carcinoma


-occasionally renal cell carcinoma contains macroscopic fat;

-CT features: exophytic, heterogeneous mass (areas of necrosis and haemorrhage), frequently contains calcifications (most reported cases); the combination of fat and calcifications should suggest the diagnosis of a malignant tumor because AML rarely contains calcifications Fig. 14 [6].





-is a fat cell malignant tumor, the 2nd most common soft-tissue sarcoma;

-it is divided histologically into 5 types: well-differentiated, myxoid, pleomorphic, round cell and dedifferentiated;

-based on the quantity and distribution of fat there are 3 CT patterns:

   · mixed: areas < -20 HU and areas > +20 HU;

   · pseudocystic: homogenous density between –20 and +20 HU;

   · solid: attenuation > +20 HU [12,13].


CT features

Exophytic renal AML

Retroperitoneal liposarcoma   Fig.15

Renal parenchymal defect at the site of tumor contact- classic ”beak sign”

Anterior displacement of the ipsilateral kidney

Dilated intratumoral vessels

Intratumoral calcifications

Supply from branches of renal artery

Non-fat-attenuating enhancing intratumoral nodules

Tumor vessels extending through the renal parenchyma- “bridging vessel sign”

Tumor vessels circumvented the kidney



Renal sinus enlargement

Multiple septae

Margins well defined and encapsulated

Poorly marginated

Associated  with other AML in syndromic cases

Varying amount of fat and soft tissue

Table 1. CT features of exophytic AML and retroperitoneal liposarcoma [12,13].



Othe tumoral entities with possible caval extension


    The spectrum of lesions that may produce IVC invasion can be divided in 2 categories, in relation to the site of origin:

-primary (extremely rare), arising from the IVC wall : leiomyosarcomas (Fig. 16,17) and leiomyomas- the most common;

-secondary (more frequent), arising from other sites: renal cell carcinoma (Fig. 18); hepatocellular carcinoma (Fig. 19); retroperitoneal tumors; adrenal cortical carcinoma (Fig. 21); Wilms tumor (Fig. 22); metastatic lymph nodes (Fig.20); renal angiomyolipoma (Fig. 8,9,10,11,12,13) and pheocromocytoma [14].



Primary IVC leiomyosarcoma


-the most common primary malignancy involving the IVC wall (75% of all large vein tumors);

-arises from parietal smooth muscle;

-US: right sided, lobulated, retroperitoneal hypoechoic mass; sometimes it is surrounded by a hyperechoic rim (Fig. 16);

-CT: large, lobulated, heterogenous mass (central low attenuation representing necrosis), contrast-media filling defect and dilatation of the IVC; hypovascular, may show peripheral enhancement following contrast injection (Fig. 17) [14,15]. 



Renal cell carcinoma


-the most common malignancy to extend into the IVC;

-CT is the first choice for imaging RCC and has a 96% accuracy in showing IVC extension; the imaging features are similar to that of other tumoral thrombus: dilated IVC and enhancement of the thrombus (Fig. 18) [14];

-MRI may suggest the likely histology: T1- heterogenous mass (due to necrosis, haemorrhage, solid components); T2- hypersignal is seen in clear cell RCC and hyposignal in papillary RCC; T1+ contrast media- prompt arterial enhancement; the presence of enhancement in the thrombus is able to distinguish between bland and tumor thrombus (Fig. 18) [16].



Hepatocellular carcinoma


-HCC patients may develop thrombosis of portal venous system, but in a minority of cases (4-5,9%) invasion of  the hepatic veins and IVC is also encountered; right atrial involvement may also be possible; all these findings predispose to distant metastases and are associated with an extremely poor prognosis [14];

-typical imaging findings are an enhancing thrombus and expansion of the hepatic veins and IVC ( Fig. 19).



Retroperitoneal lymphadenopathy


-IVC invasion can also be due to metastatic disease of the liver, kidneys or adrenal glands;

-retroperitoneal lymphadenopathies may also invade the IVC (Fig. 20) [14].  



Adrenal cortical carcinoma


-rare neoplasm, but highly malignant with a reported prevalence of 0,6 to 1,67 per million, per year;

-may present as a hormonally active (Cushing syndrome, Conn syndrome, virilisation or feminisation) or inactive tumor ; 

-CT: adrenal location, irregularly shaped, heterogeneous (secondary to necrosis or hemorrhage) and large mass (>6cm), with calcifications (up to 30% of cases), focal extension into renal vein (40% of patients), IVC, liver; metastasis to regional lymph nodes, lung, bones and liver (Fig. 21) [17].



Wilms tumor


-the most common renal neoplasm in children;

-rarely occurs in adulthood ( <1% of renal tumors, mean age=34 years);

-in childhood venous involvement is frequent (up to 45% cases; in 4-10% of pacients tumoral thrombus within IVC is present) [18]; 

-CT: heterogenous soft-tissue density masses, infrequent areas of calcifications and fat-density regions; enhancement allows for better delineation of the relationship between the mass and kidney (Fig. 22) [19].


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