Lipoma Workup
For a suspected lipoma, ultrasound is the most appropriate initial imaging modality, with high sensitivity (94.1%) and specificity (99.7%) for evaluating superficial soft tissue masses. 1, 2
Initial Clinical Assessment
Key clinical features to document:
- Size (measure in centimeters), location (superficial vs. deep), growth rate, and presence of pain 1, 3
- Lipomas typically present as soft, mobile, painless masses that are slow-growing 4
- Red flags requiring urgent evaluation: rapid growth, size >5 cm, deep-seated location, or pain 1, 3
Imaging Algorithm
First-Line Imaging
- Ultrasound is the initial test of choice for suspected superficial lipomas 1, 2
- Classic ultrasound features include: hyperechoic appearance, well-circumscribed borders, minimal to no internal vascularity on Doppler, and no acoustic shadowing 2
- Plain radiographs are of limited value, identifying intrinsic fat in only 11% of soft tissue masses 2
When to Advance Imaging
MRI is indicated when:
- Ultrasound shows atypical features (nodularity, septations, stranding) 3
- The mass is deep-seated or >5 cm 3
- There is diagnostic uncertainty between benign lipoma and atypical lipomatous tumor (ALT)/well-differentiated liposarcoma 3
- MRI can differentiate benign lipomas from ALT in up to 69% of cases 3
Role of Tissue Diagnosis
- Core needle biopsy with MDM-2 amplification analysis is the definitive test when imaging cannot distinguish between lipoma and ALT 3
- Biopsy is generally not needed for small (<5 cm), asymptomatic lesions with classic imaging features 1
Management Decision Points
Observation is Appropriate When:
- Size <5 cm, asymptomatic, and typical imaging features are present 1
- Patient has significant comorbidities making surgery high-risk 3
Surgical Excision is Indicated When:
- Symptomatic (causing pain, bleeding, or obstruction) 1, 3
- Rapidly growing 1, 3
- Size >5 cm (giant lipomas, defined as >10 cm, represent only 1% of cases but warrant evaluation) 5
- Atypical features on imaging 1
- Complete en bloc excision is the standard surgical approach with low recurrence rates 3
Common Pitfalls to Avoid
- Do not rely on physical examination alone—it correctly identifies only 85% of lipomas 2
- Do not assume all fatty masses are benign—atypical lipomatous tumors can mimic lipomas clinically but require different management 3
- Do not order MRI for every lipoma—reserve advanced imaging for lesions with concerning features or diagnostic uncertainty 1, 3
- Do not perform routine follow-up imaging after complete excision—recurrence rates are low, and re-referral is only needed if clinical suspicion of recurrence develops 3