Leiomyosarcoma is the most common primary tumor of the inferior vena cava. Incidence is higher in females between 5th and 6th decade of life (5). It is a slow growing plastic tumor that extends along the tissue planes of least resistance than directly invading the adjacent structures (7). It generally presents as a retroperitoneal lesion and is often confused with primary retroperitoneal tumors. Surgical resection is the primary therapeutic option. Imaging play a crucial role in preoperative evaluation of retroperitoneal tumors, in lesion characterization and assessment of spread. Differentiating LMS of inferior vena cava from other primary retroperitoneal tumors is a diagnostic challenge but carries high clinical implications in surgical planning. Preoperative differentiation of LMS of IVC origin from a primary retroperitoneal tumor compressing the IVC is critical because primary origin from IVC will require optimal surgical planning for vascular repair or reconstruction. LMS of inferior vena cava can be classified on the basis of the involvement of IVC and on the basis of anatomical location of the tumor.
Classification based on IVC involvement (7):
- Extraluminal- an exophytic mass lesion arising along the vascular mural wall of IVC.
- Intraluminal- soft tissue tumor within the lumen of IVC, extending along its course with high probability of extending into the right atrium.
- Mixed- shows both intraluminal and extraluminal components.
Classification based on anatomical location (8):
- Segment I: Infra renal- tumor along the infrarenal part of IVC, commonly presents with pedal edema or back ache.
- Segment II: Inter renal or supra renal- tumor is seen at the origin of renal veins or above it without obvious involvement of the hepatic veins, presents with pain abdomen and renovascular hypertension.
- Segment III: Suprahepatic- involvement of hepatic veins with or without extension into the right atrium, presents as abdominal distension, hepatomegaly, vomiting, ascites and jaundice. Rarely presents with Budd Chiari syndrome.
Common radiological features that aid in characterization of primary LMS of inferior vena cava in light of the existing literature are enumerated in table 1. In a large pooled analysis of 377 cases by Wachtel H et al (12), 133 (59.1%) cases were extraluminal, 56 (24.9%) were intraluminal and 36 (16%) cases had both intra and extraluminal components. Similar results were reported by Mingoli et al (5), where out of a total of 144 cases, 106 (73.6%) cases had predominantly extraluminal tumor and 31 (21.5%) had intraluminal involvement. Tumors with intra and extraluminal components are referred to as dumbbell tumors. Predominant intraluminal tumors and mixed tumors usually extend distally or proximally along the vascular lumen while extraluminal tumors generally show restricted or no extension as reported in our case. These tumors occur at a higher frequency in segment 2 of the IVC (i.e between the origin of renal veins and confluence of hepatic veins) followed by segment 1 (infrarenal IVC) (5, 12, 14). Tumors epicentred in the segment 2 had relatively higher incidence of extension into the hepatic veins and renal veins (3, 14, 17, 20). Tumors originating from the suprahepatic segment (segment 3) of IVC commonly have a predominantly intraluminal component and show high prevalence of intracardiac extension (5, 13, 18). Gafarli S et al reported an intraluminal tumor in segment 1 with transluminal extension into the right atrium, presenting with pulmonary thromboembolism (21). Generally, intraluminal tumors from segment 1 show distal extension in to the iliac veins (5, 15). Cortecero JM et al (13) reported an intraluminal leiomyosarcoma involving all three segments of the IVC extending into the right atrium and into the pelvis along right ovarian vein. Extraluminal LMS usually show preserved interfaces with the adjoining organs. However, infiltration into the adjacent structures is not uncommon. Owing to the proximity of IVC to aorta, encasement of aorta is seen in aggressive tumors (5, 17, 19). Extraluminal and mixed tumors with extraluminal component can also involve renal parenchyma, renal vascular pedicle and hepatic parenchyma (if occurring on right side) (9, 15, 17, 20). Involvement of adrenal gland in a mixed tumor has also been reported earlier (14). In 2004, Shvarts O et al (9) presented a mixed LMS of suprarenal (segment 2) IVC with extensive involvement of the right kidney that was initially misdiagnosed as a primary renal tumor. Li A et al (26) reported a case of large extraluminal LMS of segment 2 of the IVC that mimicked primary hepatocellular carcinoma with intravascular tumor thrombus. However in our case, fat planes with the adjacent structures were sharp with no obvious infiltration into surrounding structures.
One of the important imaging feature for characterization of retroperitoneal tumors is the relationship with IVC. Webb Em et al (27) undertook a retrospective analysis of 13 cases of retroperitoneal tumors to study the performance of four different radiological signs in differentiating LMS of IVC from other primary retroperitoneal tumors. Radiological signs that were studied are positive embedded sign, negative embedded sign, imperceptible IVC sign and tumor in lumen. They observed that imperceptible IVC lumen at the site of maximum contact is highly predictive of a IVC origin. Case described in this manuscript had the imaging feature. Prone imaging can be of diagnostic utility in demonstrating primary origin from IVC in patients with predominantly extraluminal lesion. On prone imaging, these tumors show persistent contact with the wall of IVC or persistent non visualization of the lumen of IVC. Tumors with predominant extraluminal component commonly occur in anterior relation to the IVC and towards the right side of midline (9-11, 17, 19). However, tumors originating posteriorly from the IVC have also been reported (5, 14).
These tumors commonly show heterogeneous enhancement with areas of necrosis within (9, 14, 15). Sessa B et al (10) reported inhomogeneous early enhancement followed by homogenous filling in portal venous phase. We observed inhomogeneous contrast uptake in arterial phase followed by near homogeneous enhancement in portal venous and delayed phases with non enhancing areas within. Few authors have also reported presence of calcification (16, 25) and hemorrhage (26) within the lesion.
On MR imaging LMS of IVC appears hypo to intermediately intense on T1W and hyperintense on T2W (10, 18, 26). Due to their malignant nature, these tumors also show diffusion restriction (18). Similar signal characteristics were observed in our case also.
On Positron emission tomography (PET), these tumors show mild to intense uptake of fluorodeoxyglucose (FDG) (21, 28, 29). Singh N et al (28) presented a case of intraluminal LMS showing intense FDG uptake with SUVmax value of 18. In the above presented case, the lesion showed mild FDG uptake with an SUVmax value of 4. PET CT has an indispensable role in the evaluation of intraluminal tumors in differentiating tumor thrombus from bland non tumor thrombus since these tumors present with venous thrombosis. Another significant role of PET CT lies in assessment of spread. These tumors can be locally aggressive but distant metastases are uncommon. However, lung is the most common site of metastasis (2, 11, 14). Metastasis to the liver and kidney have also been reported (11, 21).
Important differential diagnoses include retroperitoneal sarcoma and lymphoma. Lymphomas show distinctive imaging features such as homogeneous enhancement, hypointense signal on T1W and T2W showing intense diffusion restriction and avid FDG uptake. Differentiating primary retroperitoneal sarcoma from leiomyosarcoma of the IVC is challenging. However, absence of perceptible lumen of IVC at the site of maximum contact and persistent contact with the wall of IVC on prone imaging are strong predictors of IVC leiomyosarcoma.
Histopathological sampling of the tumor is performed under ultrasonographic or computed tomographic guidance. In patients with intraluminal extension of the tumor, few authors have demonstrated conventional cavagraphy based transvenous sampling (8, 24).
En bloc surgical excision with negative surgical margins remains the main stay of treatment. Being tumors of vascular origin, these tumors require vascular repair in form of primary repair or graft based on the size and location of the tumor. Achieving clear surgical margin is the most significant factor affecting survival (30). Patients with features advanced disease undergo palliative chemotherapy and radiotherapy. Patients with clear resections margins are also treated with adjuvant chemotherapy and radiation therapy. However, the benefit of adjuvant chemoradiation is unclear (14).