The value of a new diagnostic strategy for adipocytic soft tissue tumors in adults: A retrospective study

The distinction between lipoma and well-differentiated liposarcoma (WDLPS), or "atypical lipomatous tumor" (ALT), is crucial as it impacts patient management. A group of European experts led by Benjamin Moulin recently issued a consensus report to define the role of radiology in managing these lesions. It describes an algorithm defining the criteria prompting a diagnostic biopsy of deep lipomatous tumors of the limbs and chest wall. The primary aim of this study was to evaluate the algorithm's diagnostic performance.

Between 2012 and 2019, all biopsies of deep fatty tumors of the limbs or chest wall with a pre-biopsy MRI assessment were recorded at our institution. The MRI scans were reviewed by two radiologists. Each lesion was classified according to biopsy status by applying the algorithm of the European panel. The algorithm's diagnostic performance was assessed by calculating the sensitivity, specificity, positive predictive value and negative predictive value. Inter-rater agreement was also assessed.

Of the 156 tumors in our study, 148 (94.9%) required a biopsy, and the algorithm's sensitivity for detecting ALT/WDLPS was 100% with specificity of 6.3% and a PPV of 20.3%. Inter-rater agreement was almost perfect with a kappa value of 0.882.

The European algorithm demonstrates perfect sensitivity, an important criterion for a screening examination such as MRI in this setting. The algorithm's low specificity, however, emphasizes the need for further studies to redefine the optimum size cut-off value, especially for lesions without atypical criteria or an anatomical location at risk of post-surgical recurrence.