Leiomyosarcoma of the inferior vena cava.

A 84-year-old woman was recently diagnosed with an invasive ductal carcinoma of the breast. CA 15.3, a tumour marker for breast cancer, was elevated: 37.4 kU/L (normal <30 kU/L). Further past medical history was unremarkable.

Contrast-enhanced computed tomography was performed for staging purposes and
revealed a well-delineated retroperitoneal mass, which was heterogeneously enhancing (Fig. 1a). Coronal images clearly demonstrated a large mass, embedded in the vena cava inferior (IVC), located between the renal veins and the confluence of the hepatic veins (Fig. 1b, c).
On T2-weighted Images (WI), the mass was of heterogeneous signal and slightly hyperintense compared to the liver parenchyma (Fig. 2a). Diffusion-weighted images revealed restricted diffusion in the largest part of the mass, with a small focus of absent diffusion restriction (Fig. 2b).
Contrast-enhanced T1-WI revealed heterogeneous enhancement (Fig. 2c). A diagnostic surgical biopsy revealed a leiomyosarcoma of the IVC (Fig. 3).

Leiomyosarcoma (LMS) is a malignant soft tissue tumour originating from smooth muscle cells. The most common site of involvement is the uterus, but LMS can occur in any organ composed of smooth muscle cells. Primary LMS of the IVC is the most common primary tumour of the IVC and originates from the smooth muscles of the tunica media. The female to male ratio is 3:1 with a peak incidence in the sixth decade [1].
Patients are usually asymptomatic or present with non-specific abdominal complaints. The IVC is divided in three segments: Segment I between the iliac bifurcation and renal veins, segment II from the renal veins to the hepatic confluence and segment III above the hepatic confluence (Fig. 4). Depending on the side of involvement, patients can present with specific symptoms. Patients with segment I involvement can present with peripheral oedema, segment II with Budd-chiari or nephrotic syndrome and segment III with pulmonary embolism [2, 3].
Haematogenous metastases to the liver and lungs are common. Lymphatic spread is less common.
Primary LMS of the IVC is usually a large lesion at presentation with a heterogeneous contrast enhancement on CT and MRI. MRI is the best modality to evaluate the relationship to the surrounding structures. The mass typically has central necrosis, appearing as hypodense lesions on CT. On MRI these areas are hyperintense on T2-WI and show no diffusion restriction on DWI [4]. The solid part of the tumour may show diffusion restriction. In our case, the lesion displays slight tumour inhomogeneity on all sequences, but large areas of necrosis are absent.

The differential diagnosis mainly consists of retroperitoneal soft tissue tumours, intravascular leiomyomatosis, adrenal carcinoma and metastasis of testicular tumours (irrelevant in our case).

Although the location is the main clue to the correct diagnosis of leiomyosarcoma of the IVC, histopathological confirmation on biopsy is still needed for definite diagnosis.
The only curative therapy is a surgical resection with a 1 cm tumour-free margin. Because patients with primary LMS are usually diagnosed in an advanced disease stage, the overall prognosis remains poor [1].

In our patient, staging with CT of the chest and abdomen for her breast carcinoma revealed no other organ involvement or adenopathy. The diagnosis of leiomyosarcoma of the IVC was a second primary tumour as an incidental finding. The patient refused surgical procedure and preferred palliative care. For the time being, she is symptom-free and remains in follow-up.