What is a lipoma, its treatment (tx), workup, diagnostics, and physical exam?

Lipoma: Diagnosis, Workup, and Treatment

Lipomas are benign tumors composed of mature fat cells that typically require no treatment unless symptomatic, with ultrasound recommended as first-line imaging and surgical excision as the standard treatment for symptomatic cases. 1

Definition and Clinical Presentation

Lipomas are the most common benign mesenchymal tumors consisting of mature adipose tissue. They typically present as:

• Soft, rubbery, mobile masses with a characteristic doughy feel 2
• Painless, slow-growing subcutaneous tumors 3
• Most commonly found on the neck, shoulders, back, abdomen, arms, or thighs 4
• Usually small (less than 2 cm in diameter), but can occasionally grow larger 3
• Most frequently appear between 40-60 years of age 2

Physical Examination

When examining a suspected lipoma, look for:

• Round or ovoid, well-circumscribed soft tissue mass
• Mobile when manipulated (slides easily under the skin)
• Soft and doughy consistency on palpation
• Yellow hue may be visible in some cases 5
• "Pillow sign" - indentation when pressed with closed biopsy forceps (98% specificity but only 40% sensitivity) 5
• Usually non-tender unless complicated by inflammation or nerve compression

Diagnostic Workup

Imaging Studies

1. Ultrasound - First-line imaging tool for evaluating soft tissue masses 1

   • Shows well-defined, homogeneous, hyperechoic mass

2. MRI - Most accurate for diagnosis and surgical planning in cases of uncertainty 1

   • Particularly useful for extremity, trunk, and pelvic soft tissue tumors
   • Helps distinguish lipomas from atypical lipomatous tumors or liposarcomas

3. CT scan - Used for retroperitoneal or intrathoracic lipomas 1

4. Plain radiographs - Useful for identifying bone involvement or calcification 1

Biopsy

• Percutaneous core needle biopsy with MDM-2 amplification testing may be recommended for diagnostic uncertainty 1
• Helps distinguish between simple lipomas and atypical lipomatous tumors

Treatment Approaches

Treatment decisions should be based on:

• Size of the lipoma
• Location
• Symptoms
• Cosmetic concerns
• Patient preference

Observation

• Small (<5 cm), asymptomatic lipomas can be safely observed 1
• Indications for intervention include:
  • Growth in size
  • Pain
  • Cosmetic concerns
  • Functional interference

Surgical Management

1. Standard wide excision - First-line treatment for symptomatic lipomas 1

   • Involves removal of the tumor with a rim of normal tissue
   • Associated with lower recurrence rate (approximately 3.3%)

2. Marginal excision - Acceptable for carefully selected cases 1

   • Particularly for extracompartmental atypical lipomatous tumors
   • Recurrence rate of 7.5-13.9%

3. Minimally invasive techniques 1

   • 1-inch method or liposuction may be considered for:
     • Cosmetically sensitive areas
     • Large lipomas

Special Considerations

By Location

• Intramuscular lipomas (e.g., in biceps brachii) - May require MRI for proper evaluation 6
• Deep-seated lipomas - Require wide excision with negative margins 1
• Gastric lipomas - Rare (1% of gastric intramural lesions), may cause bleeding, obstruction, or abdominal pain 5
  • Endoscopic ultrasound shows intensely hyperechoic well-circumscribed mass in submucosal layer

By Size

• Giant lipomas (>10 cm or >1000g) - May cause functional limitations, lymphedema, pain syndromes, or nerve compression 3
• Large lipomas (>5 cm) - May require minimally invasive techniques or wide excision 1

Variants

• Atypical lipomatous tumors - Require complete en bloc resection 1
• Multiple Symmetrical Lipomatosis - May require surgical removal in several sessions 1
• Other variants include angiolipomas, neomorphic lipomas, spindle cell lipomas, and adenolipomas 2

Follow-Up and Prognosis

• Long-term follow-up is warranted as recurrences can occur late (mean 4.7 years after resection) 1
• Subcutaneous lipomas have excellent prognosis with low risk of malignant transformation 1
• Risk of dedifferentiation is approximately 1-1.1% in extremity atypical lipomatous tumors 1

Important Pitfalls to Avoid

• Misdiagnosis: Always distinguish lipomas from liposarcomas, which can have similar appearance 2
• Inadequate imaging: Use appropriate imaging modalities based on location and clinical suspicion
• Unnecessary biopsies: Most superficial lipomas can be diagnosed clinically without biopsy
• Incomplete excision: Ensure complete removal to prevent recurrence
• Overlooking rare syndromes: Consider hereditary multiple lipomatosis, adiposis dolorosa, Gardner's syndrome, and Madelung's disease in patients with multiple lipomas 2