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Keywords:

  • retroperitoneal liposarcoma;
  • imaging;
  • atypical lipomatous tumor;
  • well differentiation;
  • dedifferentiation

Abstract

BACKGROUND:

Well differentiated (WD) and dedifferentiated (DD) retroperitoneal liposarcoma (RPLS) have distinct biologic behaviors. Consequently, the therapeutic approaches for these tumors differ and mandate an accurate preoperative diagnosis. The authors of this report evaluated whether computed tomography (CT) can be used to differentiate between WD and DD RPLS.

METHODS:

Imaging studies (CT, magnetic resonance imaging, and positron emission tomography-CT) from 78 patients with RPLS who underwent surgery at the University of Texas M. D. Anderson Cancer Center (UTMDACC) between 2001 and 2007 were reviewed by a senior bone and soft tissue sarcoma radiologist who was blinded to the final histopathologic diagnosis. A focal nodular/water density area within an RPLS was interpreted as a marker suggestive of DD. Correlations between imaging diagnosis, histology, and clinical outcome were analyzed.

RESULTS:

The study radiologist identified 60 RPLS as DD and 17 RPLS as WD. A radiologic diagnosis of a WD was correlated with preoperative biopsy and postoperative histology in all patients (100%). Focal nodular/water density was a very sensitive marker of DD (97.8%); however, it had relatively low specificity (51.5%). Sixteen WD RPLS (48.5%) contained focal nodular/water density areas, leading to their misdiagnosis as DD; half of those tumors had hypercellular WD. Of 78 preoperative biopsies, 22 (28.2%) were performed at UTMDACC under CT guidance. Preoperative histologic diagnoses obtained from 12 biopsies derived from focal nodular/water density areas were confirmed as unchanged on final pathology; whereas, in 50% of biopsies that were not taken from a suspicious area, DD histology was misdiagnosed as WD.

CONCLUSIONS:

When CT features are suggestive of WD, no further diagnostic tests are needed for tumor characterization. Moreover, CT can accurately identify most DD, thereby rendering their under-treatment unlikely; however, a CT-guided biopsy is needed to differentiate between DD and WD RPLS that contain focal nodular/water density areas, thereby avoiding their over treatment. Cancer 2009. © 2009 American Cancer Society.