From the Guidelines
The presence of septations within a lipoma does not necessarily indicate malignancy, but rather may be associated with atypical lipomatous tumors (ALT) or well-differentiated liposarcoma (WDL), and therefore, further evaluation with MRI and expert review is recommended to differentiate between large, deep lipomas and ALT/WDL, as reported in the UK guidelines for the management of soft tissue sarcomas 1.
Clinical Implications
The variables of nodularity, septations, stranding, and relative size show an association with the diagnosis of ALT/well-differentiated liposarcoma 1. However, the defining diagnostic test to differentiate between lipomas and ALT/well-differentiated liposarcoma is the molecular demonstration by fluorescence in-situ hybridisation of amplification of the MDM-2 cell cycle oncogene, which can be done on percutaneous core needle biopsy if the diagnosis of ALT is suspected 1.
Management
Surgical resection is the usual treatment for ALT, and the prognosis is mostly excellent 1. However, in older patients, if surgery is likely to be morbid or the patient has significant comorbidities, radiological surveillance can be considered 1. In larger tumours, or those where clear margins are difficult to achieve, adjuvant radiotherapy may occasionally be considered 1.
Key Points
- Septations within a lipoma may be associated with ALT or WDL
- MRI with expert review can help differentiate between large, deep lipomas and ALT/WDL
- Molecular demonstration by fluorescence in-situ hybridisation is the defining diagnostic test
- Surgical resection is the usual treatment for ALT, with excellent prognosis
- Radiological surveillance or adjuvant radiotherapy may be considered in certain cases, as reported in the UK guidelines for the management of soft tissue sarcomas 1.
From the Research
Presence of Septations in Lipoma
- Septations are a key feature in differentiating between benign and malignant lipomatous tumors 2, 3, 4.
- The presence of septations, particularly thick septations, is more commonly associated with malignant tumors such as liposarcoma 3, 4.
- A study found that septum-like structures in liposarcoma are thick and enhance considerably on fat-suppressed T1-weighted images after Gd-DTPA administration, whereas septa of lipoma are thin and enhance only slightly 4.
- Another study suggested that the presence of septations, along with other features such as nodules and heterogeneity, can be used to identify high-risk radiographic features that may indicate malignancy 2.
Diagnostic Accuracy
- The diagnostic accuracy for differentiating between benign, intermediate-grade, and malignant lipomatous tumors does not improve with the addition of contrast-enhanced sequences, diffusion-weighted imaging (DWI), or chemical shift imaging (CSI) to a conventional, noncontrast MRI protocol 5.
- Noncontrast features, including thick septations and nodules ≥ 1 cm, are useful for differentiating benign tumors from atypical lipomatous tumors (ALTs) and dedifferentiated liposarcomas (DDLs) 5.
- DWI and CSI metrics may also be helpful in distinguishing between these entities 5.
Clinical Implications
- The presence of septations within a lipoma may indicate a higher risk of malignancy, and further evaluation with imaging and/or biopsy may be necessary 2, 3.
- Surgical resection with a wide surgical margin is the treatment of choice for liposarcoma, and the presence of septations may affect the extent of surgical procedures required 6, 4.