Primary dedifferentiated liposarcoma of the retroperitoneum. Prognostic significance of computed tomography and magnetic resonance imaging features.

OBJECTIVES

To describe computed tomography (CT) and magnetic resonance (MR) imaging findings and to determine the prognostic significance of radiologic appearances in primary dedifferentiated liposarcoma of the retroperitoneum.

METHODS

Initial CT and MR imaging studies of 20 pathologically confirmed cases of primary dedifferentiated liposarcoma of the retroperitoneum were retrospectively reviewed and assessed for correlations with the histopathologic features. CT and MR images were evaluated by 2 radiologists with agreement by consensus, and univariate analyses were conducted to evaluate survival with a mean clinical follow-up duration of 47 months (range, 5-114 months).

RESULTS

Tumor invasion was more frequent in the anterior or posterior pararenal originating tumors than in pararenal tumors (P<0.05). Well-defined nonlipomatous masses juxtaposed with fatty tumors were identified in all cases. Calcification or ossification was seen in 6 patients (30%) on unenhanced CT. Imaging findings including attenuation, signal characteristics, and enhancement patterns of nonlipomatous masses were nonspecific regardless of histologic variances. Recurrent tumors (n=6) tended to invade surrounding organs. Univariate analysis revealed that calcification or ossification (P<0.05) and first recurrence with duration of a mean 13 months (P<0.05) identified by imaging studies had significant impacts on overall survival.

CONCLUSIONS

Calcification or ossification and first recurrence identified by CT and MR imaging studies are significant adverse prognostic factors in primary dedifferentiated liposarcoma of the retroperitoneum.