The former is the most common variant and is a particular consideration in the differential diagnosis given its microscopic similarity to lipoma; the presence of atypical stromal cells and lipoblasts points towards malignancy, while, in equivocal cases, immunohistochemistry reveals MDM2 and CDK4 positivity, and molecular analysis by FISH demonstrates MDM2 gene amplification in atypical lipomatous tumors [17,18]. Here, CDK4 is linked to lipoma.