Widespread mediastinal - retroperitoneal tumour

Clinical History

The patient presented to the hospital with dyspnoea, rapid onset of high blood pressure, fatigue, urinary disturbances. The internist suggested an abdominal CT and evaluation of the renal arteries with AngioCT.

Imaging Findings

Main CT finding was a huge solid mass that extended from posterior mediastinum around the main vessels to the lower retroperitoneal space (Fig 1, 2). It presented like a mantel with net-like calcification, which had weak enhancement by contrast media, around inferior vena cava and left perirenal space, causing inferior vena cava infiltration and obstruction of middle portion of right renal artery and of the proximal right ureter and resulting in right renal second degree hydronephrosis (Fig 3, 4). We found free fluid in right pleural space, but no other changes in lungs (Fig 1). We noticed a small subcutaneus nodule with the same imaging characteristics with mass in left flank (Fig 3a, 3c, 4f). Magnetic Resonance was not available. Unusual form of retroperitoneal fibrosis was assumed, and therefore histology of materials from the mass and the subcutaneus nodule was performed. The result was retroperitoneal fibrosis with high degree of malignancy.

Discussion

Retroperitoneal fibrosis (RPF) is a rare fibrotic reactive process with a prevalence of about 1 per 200,000 population. It is considered a member of a family of disorders referred to as chronic periaortitis.[1, 2] Two thirds of all cases of RPF are considered idiopathic (also called Ormond's disease), and approximately one third of cases develop in response to various medications, malignancies, or other aetiologies.[1, 3] Idiopathic RPF occurs more commonly in men by a ratio of 2:1, [1, 4] and RPF associated with malignancy occurs equally in men and women. [1] Most patients with RPF present during the fifth or sixth decade of life. [4, 5]
The exact aetiology of idiopathic RPF is unclear an underlying systemic autoimmune process is believed to be responsible instead. [2] In up to 15% of individuals with RPF, associated fibrotic processes outside the retroperitoneum may be present, including fibrosing mediastinitis, sclerosing mesenteritis, orbital pseudotumour, primary sclerosing cholangitis, and Reidel's thyroiditis. [5, 9] Other autoimmune or inflammatory disease processes also have an association with RPF. [3, 6]
Malignant RPF, an unusual subtype of RPF, is clinically difficult to distinguish from RPF due to benign or idiopathic causes. Malignant RPF occurs when small metastatic foci to the retroperitoneum (usually from lymphoma) elicit a desmoplastic response, although any primary malignancy may be involved. [1, 5, 7]
Other conditions that can lead to RPF may be infections; nonspecific gastrointestinal inflammation including Crohn's disease; retroperitoneal haemorrhage; urine extravasation; or prior irradiation or surgery. [1, 3, 5]
On CT, RPF has homogeneous soft tissue attenuation similar to or slightly greater than that of skeletal muscle. [1, 5, 9]
On MRI, the T2-weighted signal intensity of RPF depends on the activity of the disease. RPF has low to intermediate signal intensity on T1-weighted imaging; on T2-weighted imaging, mature fibrotic plaque in benign RPF has low signal intensity, whereas immature fibrotic plaque in benign RPF and malignant RPF has higher signal intensity because of inflammatory oedema or hypercellularity. Enhancement of RPF on CT and MRI is variable and depends on the maturity of the fibrous process. [1, 7, 8, 9]
Imaging findings that suggest malignant RPF include the presence of other lymphadenopathy or metastatic disease, adjacent osseous destruction, a heterogeneous soft tissue mass with poorly defined margins, and associated high-signal-intensity changes of the adjacent psoas muscles on T2-weighted imaging.
The prognosis for patients with malignant RPF is poor, with a mean survival of 3 to 6 months after diagnosis. [5, 9]

Differential Diagnosis List

Final Diagnosis

Malignant retroperitoneal fibrosis

URL:	https://www.eurorad.org/case/10644
DOI:	10.1594/EURORAD/CASE.10644
ISSN:	1563-4086