Lipomas are common benign tumors composed of mature adipocytes, usually presenting as soft, mobile, painless subcutaneous nodules on the trunk, shoulders, neck, or extremities. Most are solitary and small (<5 cm), but multiple lesions can occur, including in familial multiple lipomatosis. While typically asymptomatic, lipomas may cause discomfort due to size, location, or cosmetic concerns. Diagnosis is clinical; imaging is reserved for deep, rapidly enlarging, atypical, or painful lesions to exclude liposarcoma. Treatment is elective; options include surgical excision (definitive) and minimally invasive techniques such as liposuction for select cases.
Epidemiology and Risk Factors
- Peak in adults 40–60 years; slight male predominance in some series.
- Risk factors: genetics (familial multiple lipomatosis; syndromes like PTEN hamartoma tumor syndrome, MEN1, Gardner syndrome), obesity not clearly causal.
- Variants: angiolipoma (often tender), fibrolipoma, spindle cell/pleomorphic lipoma (distinct histology, usually posterior neck/shoulder of older men), intramuscular/infiltrating lipoma, lipoblastoma (children).
Clinical Features
- Soft, doughy, lobulated, well-circumscribed subcutaneous mass; freely mobile over underlying structures.
- Size typically 1–5 cm; can slowly enlarge over years.
- Angiolipomas are firmer, often multiple on forearms, and tender.
- Deep or intramuscular lipomas feel less mobile and can be larger.
Differential Diagnosis
- Epidermal inclusion cyst, liposarcoma (particularly atypical lipomatous tumor/well-differentiated liposarcoma), lymphadenopathy, hematoma, neurofibroma, elastofibroma dorsi (scapular region), hernia (abdominal wall), xanthomas (tendinous).
Diagnosis and Workup
- Clinical diagnosis for typical small, superficial, slow-growing lesions.
- Imaging when atypical:
- Ultrasound: homogenous, hyperechoic mass with thin capsule.
- MRI: characteristic high T1 signal suppressed on fat-sat; septations <2 mm favor benign lipoma; thick septa, nodularity, or nonfatty areas raise concern for ALT/WDL.
- Biopsy rarely required unless imaging or clinical features are suspicious (rapid growth, pain, size >5–10 cm, deep location, firm/fixed, neurologic symptoms).
Management
- Observation if asymptomatic and typical.
- Excision:
- Indications: pain, rapid growth, functional limitation, cosmetic reasons, diagnostic uncertainty.
- Technique: longitudinal incision over lesion; blunt dissection to shell out encapsulated mass; hemostasis; layered closure. Recurrence is rare if complete.
- Complications: seroma, hematoma, infection, scarring; higher risk with larger/deep lesions.
- Liposuction-assisted removal:
- For large, soft, subcutaneous lipomas in favorable locations to minimize scarring; higher recurrence if capsule remnants remain.
- Angiolipomas: excision for symptomatic lesions; often multiple.
Counseling and Follow-up
- Benign with minimal malignant potential; transformation is exceedingly rare—concern is misdiagnosis.
- Return if rapid change, pain, firmness, fixation, or neurologic deficits.
References (recent guidelines and key reviews)
- Imaging characteristics distinguishing lipoma from ALT/WDL, 2021–2024.
- Surgical techniques and outcomes for lipoma excision vs liposuction, 2021–2024.
- Syndromic associations with multiple lipomas, 2022–2024.