Imaging differentiation/lipoma/dedifferentiated liposarcoma and well-differentiated liposarcoma

Lipomatous lineage tumors are common lesions in soft tissues, primarily in subcutaneous tissue and occasionally in deeper areas. Lipomas, benign tumors, are the most common and represent 50% of all soft tissue tumors. They consist of mature adipose tissue and exhibit typical imaging characteristics on magnetic resonance imaging (MRI). However, when these mesenchymal tumors present dedifferentiated elements and their appearance does not show typical findings of either a lipoma or a liposarcoma, they are considered within the group of “atypical” lipomatous tumors, neoplasms that often have a relatively benign course when occurring in the extremities compared to their retroperitoneal counterparts. These types of tumors do not usually metastasize; however, they have high rates of local recurrence and a potential for late dedifferentiation into higher-grade sarcomas with metastatic potential. On the other hand, liposarcomas, less common, are distinguished by their location in deeper planes and have a different appearance on MRI, with masses showing fatty intensity, irregular septa, and non-adipose areas. We will highlight, through literature review, the utility of MRI in the identification and differentiation of lipomatous lineage lesions.