Is an ultrasound appropriate for an elderly female patient with a 2-month history of a painful, movable nodule on the right lower leg, presenting with moderate pain and no acute sharp pain?

Ultrasound for Lower Leg Nodule Evaluation

Yes, ultrasound is highly appropriate as the first-line imaging modality for this elderly patient with a painful, movable nodule on the lower leg that has been present for 2 months. 1

Initial Imaging Algorithm

Begin with plain radiographs of the lower leg before ultrasound. 1, 2 Radiographs should be obtained first to identify:

• Calcification within the mass (present in 27% of soft tissue masses) 2
• Bone involvement or cortical erosion (present in 22% of cases) 2
• Intrinsic fat content (visible in 11% of soft tissue masses) 1, 2

Following radiographs, proceed immediately to ultrasound examination. 1 Ultrasound has emerged as the most useful initial imaging for suspected superficial soft tissue masses, with sensitivity of 86.87-94.1% and specificity of 95.95-99.7% for superficial lesions. 1, 2

What Ultrasound Will Reveal

The ultrasound examination should characterize:

• Mass composition: Whether the nodule is solid versus cystic, with ability to confirm fluid content if present 2
• Echogenicity pattern: Lipomas appear hyperechoic or isoechoic with thin curved echogenic lines, while other masses have distinct patterns 1
• Vascularity: Doppler assessment for internal blood flow (benign lipomas show minimal to no vascularity) 1
• Relationship to surrounding structures: Including proximity to neurovascular bundles, tendons, and bone 2
• Capsule characteristics: Well-circumscribed masses with thin capsules suggest benign pathology 1

Critical Red Flags Requiring Advanced Imaging

If ultrasound demonstrates any of the following features, proceed directly to MRI: 1

• Size larger than 5 cm 1
• Deep location (subfascial or intramuscular) 1
• Atypical ultrasound features (thick septations, nodularity, heterogeneous appearance) 1
• Significant internal vascularity on Doppler 1

Important Caveat for Lower Leg Location

The lower leg location warrants heightened vigilance. 1 Deep-seated lipomatous masses in the lower limb have increased concern for atypical lipomatous tumor (well-differentiated liposarcoma), which requires different surgical management than simple lipoma. 1 If the mass is deep to the fascia or demonstrates concerning features on ultrasound, MRI with expert review should be obtained to assess for features of malignancy including nodularity, thick septations, and stranding. 1

When Ultrasound Is Insufficient

Ultrasound is considerably less accurate for deep masses compared to superficial ones. 1 If the nodule is:

• Located deep to the fascia 1
• In an anatomically complex area 2
• Demonstrates rapid growth despite initial benign appearance 1

Then MRI without and with contrast becomes the preferred imaging modality for definitive characterization and surgical planning. 3, 2

Practical Advantages of Ultrasound in This Case

For this specific clinical scenario, ultrasound offers:

• Real-time dynamic assessment during palpation to correlate clinical findings with imaging 4
• Point-of-care evaluation that can be performed during the clinical encounter 5
• Cost-effectiveness compared to MRI for initial triage 5
• Ability to guide biopsy if tissue sampling becomes necessary 3, 2

Next Steps Based on Ultrasound Findings

If ultrasound shows benign characteristics (well-circumscribed, hyperechoic, no vascularity, superficial location <5 cm): Consider observation versus excision based on symptoms. 1, 2

If ultrasound shows concerning features or diagnostic uncertainty: Obtain MRI with contrast, and if MRI demonstrates worrisome features, proceed to core needle biopsy with MDM-2 amplification analysis to exclude atypical lipomatous tumor. 1