Abdominal distension

Clinical History

A 52-year-old female patient presented with abdominal distension and non-specific abdominal discomfort.

Imaging Findings

A 52-year-old female patient presented with abdominal distension and non-specific abdominal discomfort. A plain abdominal film was obtained (Fig. 1a), which showed that there was a mass effect with loss of the retroperitoneal anatomical landmarks (left psoas line and left renal contour). Bizarre calcifications were identified on the left hemipelvis. An abdominal ultrasonographic study was done, which showed that there was a huge space-occupying lesion with areas of different echogenicity (Fig. 2a, b). The mass, in the upper portion was predominatly hyperechoic, a finding very suggestive of and corresponding to a fatty component. The lesion in the lower portion (Fig. 2b) presented a more solid appearance. Helical computed tomography performed after intravenous contrast administration showed that the mass, with areas of fatty and solid attenuation values, was displacing the surrounding organs, and engulfing the left kidney (Fig. 3a, b, c). Pelvic calcifications inside the tumoral mass were identified. A magnetic resonance imaging study, with the T2-weighted technique (Fig. 4a, b), and T1-weighted images with contrast administration and fat-suppressed sequences (Fig. 4c, d), gave images which showed the huge lesion with areas of fatty component. The dynamic study after intravenous administration of gadolinium (Fig. 4c, d) showed the hypervascular nature of the lesion.

Discussion

Liposarcomas are one of the most common malignant tumors of soft tissues. They are also one of the most frequently occurring retroperitoneal sarcomas. At gross examination, a liposarcoma is seen to form nodular masses of a soft myxoid character, yellow in color, that present areas of hemorrhage and necrosis. It may reach a large size, not infrequently be circumscribed, and appear to be encapsulated, although it always infiltrates. Five histological types have been described: sclerosing and lipoma-like, both of them well-differentiated with abundant mature fat cells; pleomorphic, round cell and myxoid, the latter three ill-differentiated with relatively little fat. So the radiological appearance of this tumor is varied depending on the degree of differentiation and the variable amount and distribution of fat within it. Several distinct radiological patterns have been described: poor differentiated tumors with little fat appear as having a solid pattern, while well-differentiated tumors will demonstrate a mixed pattern with fatty areas and others appear with higher attenuation values. In other cases, the tumor appears as a homogeneous low density mass, which is indistinguishable from normal fat or a lipoma. Nowadays, the magnetic resonance technique has been demonstrated to be very useful in confirming the presence of fatty areas by means of different specific sequences of imaging, as well as in the evaluation of the morphological features of this kind of pathology. Leiomyosarcomas are usually large tumors with areas of necrosis and hemorrhage but they do not present a fatty component. Intra-abdominal fibromatosis, the most common of the primary solid tumors of the mesentery, are growths of fibroblastic tissue that can be locally aggressive, but do not metastasize, composed of fibroblastic cells in a collagenous stroma of varying density. Inflammation and necrotic or neoplastic changes are absent. The radiological appearance of these lesions depends on the relative amounts of fibrosis, collagen content and vascularity of the tumor.

Differential Diagnosis List

Final Diagnosis

Retroperitoneal liposarcoma.

URL:	https://www.eurorad.org/case/3470
DOI:	10.1594/EURORAD/CASE.3470
ISSN:	1563-4086