Developing a Diagnostic Model to Differentiate the Well-differentiated Lipomatous Tumors Based on Clinicopathological Characteristics

This study evaluated the diagnostic value of clinicopathological features and immunohistochemical markers for distinguishing lipomas from atypical lipomatous tumors/well-differentiated liposarcomas (ALTs/WDLTs). An integrated diagnostic model for ALTs/WDLTs was developed to provide guidance for diagnosis, treatment planning, and prognosis. A retrospective analysis was conducted on 216 lipomatous tumor cases diagnosed between February 2018 and December 2024, including lipomas (n = 149), spindle cell lipomas (n = 3), ALTs/WDLTs (n = 62), and early de-differentiated liposarcomas (n = 2). Immunohistochemical data for MDM2, CDK4, and p16 were available for 131 patients. MDM2 amplification was significantly more frequent in patients ≥ 55 years and in tumors of the lower limbs (especially thigh) and retroperitoneum (p = 0.000). Larger tumor size and multiplicity were also associated with MDM2 amplification (p < 0.05). Immunohistochemistry sensitivities for ALTs/WDLTs vs. lipomas: 65% (MDM2), 100% (CDK4), 80.39% (p16); combined, specificity was 100% and sensitivity 85.58%. The diagnostic model achieved 93.33% sensitivity and 72.22% specificity. Scores < 0.2191 indicated a higher likelihood of lipoma, while scores > 0.6521 indicated a higher likelihood of liposarcoma. Age ≥ 55, lower extremity/retroperitoneal location, tumor diameter ≥ 9.9 cm, and positive markers were independent risk factors. This model provides an effective tool for ALT/WDLT identification.