Physical Examination Characteristics of Lipoma
Lipomas present as soft, rubbery, mobile masses with a characteristic "doughy" feel that are typically painless and move easily when touched. 1
Classic Physical Examination Features
Palpation Characteristics
- Soft, doughy consistency that distinguishes lipomas from firmer masses 1
- Mobile and freely movable under the skin when palpated 1, 2
- Round or ovalar shape with smooth contours 3
- Non-tender in most cases, though pain may indicate atypical features requiring further evaluation 4, 5
Size and Location
- Most lipomas are small, ranging from less than 1 inch to a few inches in diameter 6
- Lipomas larger than 10 cm are classified as "giant lipomas" and represent only 1% of all lipomas 6, 7
- Most commonly located on the neck, shoulders, back, abdomen, arms, or thighs 6, 1
- Can occur in subcutaneous tissue (most common), subfascial, intramuscular, or other anatomical locations 7
Critical Limitations of Physical Examination Alone
Physical examination correctly identifies only approximately 85% of lipomas, making imaging essential for definitive diagnosis. 4
Red Flags Requiring Advanced Evaluation
- Size greater than 5 cm warrants imaging to exclude atypical lipomatous tumor 4, 5
- Rapid growth or recent change in size raises concern for malignancy 4, 5
- Pain or tenderness is atypical and requires further investigation 4, 5
- Deep-seated location, particularly in the lower limb, increases risk of atypical lipomatous tumor 4
- Firm consistency rather than soft/doughy texture suggests alternative diagnosis 1
Recommended Diagnostic Approach
Initial Imaging
- Ultrasound is the first-line imaging modality for suspected superficial lipomas, with sensitivity of 94.1% and specificity of 99.7% 4, 5
- Characteristic ultrasound features include well-circumscribed, hyperechoic appearance with minimal internal vascularity and thin, curved echogenic lines (the "striped" pattern) 4, 8, 3
When to Escalate Beyond Physical Exam
- Any lipoma with atypical features on palpation (firm, fixed, painful, rapidly growing) requires ultrasound evaluation 4, 5
- Deep-seated masses or those larger than 5 cm require MRI to differentiate benign lipoma from atypical lipomatous tumor, which can be achieved in up to 69% of cases 9, 4
- MRI showing nodularity, thick septations, or stranding necessitates core needle biopsy with MDM-2 amplification analysis 9, 4
Common Clinical Pitfalls to Avoid
- Do not rely solely on physical examination for diagnosis, as 15% of lipomas are misidentified clinically 4
- Do not assume all soft, mobile masses are benign lipomas—atypical lipomatous tumors can have similar presentation but require different surgical management 9
- Do not dismiss deep-seated or lower limb lipomas without imaging, as these have heightened risk for atypical lipomatous tumor 4