When is referral necessary for a patient with a lipoma?

When to Refer a Lipoma

Most lipomas do not require referral and can be managed in primary care with observation or office-based excision, but you must refer to a sarcoma center or surgical oncologist if the mass is >5 cm, deep-seated (subfascial/intramuscular), rapidly growing, painful, or located in the retroperitoneum or abdomen. 1, 2

Red Flags Requiring Mandatory Specialist Referral

Refer immediately to a sarcoma multidisciplinary team if ANY of the following are present:

• Size >5 cm in any dimension – this is a hard cutoff that requires specialist evaluation to exclude atypical lipomatous tumor (ALT)/well-differentiated liposarcoma 1, 2
• Deep location (subfascial or intramuscular) – these have higher risk of being ALT and require specialized surgical planning 1, 2
• Retroperitoneal or intra-abdominal location – these mandate sarcoma MDT evaluation before any intervention 2
• Rapid growth – any lipoma increasing quickly in size needs urgent assessment 1, 2
• Pain – lipomas are typically painless; pain suggests alternative diagnosis or complications 1, 2
• Atypical imaging features on ultrasound or MRI – including nodularity, thick septations, or concerning characteristics that suggest ALT 1, 2

Initial Diagnostic Workup in Primary Care

Before deciding on referral, obtain appropriate imaging:

• Start with ultrasound for suspected superficial lipomas – this has 94.1% sensitivity and 99.7% specificity 3, 2
• Classic ultrasound features of benign lipoma include: hyperechoic appearance, well-circumscribed borders, minimal/no internal vascularity on Doppler, and no acoustic shadowing 3, 2
• Plain radiographs are not useful – they identify intrinsic fat in only 11% of soft tissue masses 3, 2
• Order MRI if ultrasound shows atypical features, the mass is deep-seated, >5 cm, or there is diagnostic uncertainty between benign lipoma and ALT 2

Critical pitfall: Physical examination alone correctly identifies only 85% of lipomas, so imaging is essential 3. MRI can differentiate benign lipomas from ALT in only 69% of cases, meaning tissue diagnosis may still be needed 1, 2.

Location-Specific Considerations

• Deep extremity or lower limb masses have higher suspicion for ALT and warrant sarcoma specialist evaluation 2
• Breast lipomas in women ≥40 years may require mammography, and if correlation between clinical exam and imaging is unclear, ultrasound confirmation is needed 4, 2
• Superficial trunk/extremity lipomas <5 cm with typical imaging features can be managed in primary care 2

When Primary Care Management is Appropriate

You can manage without referral if ALL of the following criteria are met:

• Superficial location (subcutaneous only) 2
• Size <5 cm 1, 2
• Typical imaging features on ultrasound (hyperechoic, well-circumscribed, minimal vascularity) 3, 2
• Asymptomatic or minimally symptomatic 2
• No rapid growth 1, 2

For these benign-appearing lipomas, options include:

• Observation for asymptomatic lesions with typical features 2
• Office-based excision using complete en-bloc technique with negative margins if symptomatic or patient desires removal 2

Why This Matters for Patient Outcomes

The critical distinction is between benign lipoma and ALT/well-differentiated liposarcoma, which fundamentally changes surgical approach. 1, 2 ALT requires wide excision by sarcoma specialists because:

• Inadequate excision leads to high local recurrence rates 2
• Progressive dedifferentiation can occur with each recurrence 2
• Simple "shelling out" of ALT (appropriate for lipoma) results in treatment failure 2

Definitive diagnosis requires percutaneous core biopsy for MDM-2 amplification testing when suspicion of ALT exists, which should be coordinated by the sarcoma center before any surgical intervention 1, 2. MRI features suggesting ALT include larger size, deep location (especially lower limb), nodularity, septations, and stranding 1.