Can an ultrasound (ultrasonography) detect sarcoma?

Can Ultrasound Detect Sarcoma?

Yes, ultrasound can detect sarcoma and is recommended as the first-line imaging modality for evaluating suspicious soft tissue masses, with high sensitivity (94.1%) and specificity (99.7%) for discriminating benign from malignant lesions. 1

Evidence Supporting Ultrasound for Sarcoma Detection

Guideline Recommendations

The most recent UK guidelines (2025) from the British Journal of Cancer, incorporating NICE guidance, explicitly recommend ultrasound as the primary diagnostic tool: 1

• Urgent ultrasound scan (within 2 weeks) should be performed for any adult with an unexplained lump that is increasing in size 1
• Ultrasound provides an effective initial triage tool that can identify features suggestive of sarcoma and safely reassure patients with benign findings 1
• Patients with ultrasound findings suggestive of soft tissue sarcoma should be referred via a suspected cancer pathway for specialist evaluation within 2 weeks 1

What Ultrasound Can Show

Ultrasound is particularly effective at identifying concerning features that warrant further investigation: 1, 2

• Heterogeneous echotexture in a soft tissue mass 2
• Disorganized internal vascularity on Doppler examination (as opposed to minimal or linear vascularity in benign lesions) 2, 3
• Infiltrative or poorly defined margins (rather than well-circumscribed borders typical of benign lesions) 2, 4
• Size greater than 5 cm combined with other suspicious features 3
• Deep location relative to fascia 4

Important Limitations and When to Proceed to MRI

While ultrasound is highly effective, it has critical limitations that must be recognized: 1

Ultrasound is User-Dependent

In cases of diagnostic uncertainty on ultrasound, MRI of the affected region must be performed 1. This is a crucial safety net, as ultrasound interpretation varies significantly with operator experience. 1

Deep-Seated Masses Require Advanced Imaging

• For soft-tissue tumors affecting the extremity, trunk, and pelvis, MRI provides the most accurate information for diagnosis and surgical/radiotherapy planning 1
• Ultrasound is considerably less accurate for deep lipomas compared to superficial ones 2
• All deep-seated lipomas or those in the lower limb should raise concern for atypical lipomatous tumors (well-differentiated liposarcomas) 2

Retroperitoneal and Intra-Abdominal Masses

For retroperitoneal tumors and intra-thoracic sarcomas, CT is preferred for diagnosis and treatment planning 1. Ultrasound is not appropriate for these locations. 1

Clinical Algorithm for Using Ultrasound

Step 1: Initial Assessment

• Any unexplained soft tissue lump that is increasing in size warrants urgent ultrasound within 2 weeks 1
• Clinical red flags include: size >5 cm, deep location, pain, or rapid growth 1

Step 2: Ultrasound Interpretation

• Benign features (well-circumscribed, hyperechoic/isoechoic to fat, minimal vascularity): Most can be safely observed or managed locally 1, 2
• Suspicious features (heterogeneous, disorganized vascularity, infiltrative margins, size >5 cm with internal blood flow): Proceed to Step 3 2, 3
• Uncertain findings: Proceed to MRI 1

Step 3: Referral and Advanced Imaging

• Refer to specialist sarcoma multidisciplinary team within 2 weeks 1, 5
• Obtain MRI for definitive characterization and surgical planning 1, 5
• Perform CT chest for staging if sarcoma is confirmed 1, 5

Common Pitfalls to Avoid

Do Not Rely Solely on Ultrasound for Deep Masses

The accuracy of ultrasound drops significantly for deep-seated lesions 2. Any mass deep to the fascia, particularly in the thigh or retroperitoneum, requires MRI or CT regardless of ultrasound appearance. 1, 2

Do Not Dismiss Masses >5 cm Even with "Benign" Ultrasound Features

Size >5 cm is an independent risk factor for malignancy 3. In a study of soft tissue masses, even among those initially appearing benign on ultrasound, larger lesions had higher rates of malignancy on follow-up. 4

Do Not Confuse Hematoma with Sarcoma

Sarcomas are commonly misdiagnosed as hematomas, especially with a history of mild trauma 3. Key distinguishing features include: 3

• Internal vascular Doppler flow (present in sarcoma, absent in hematoma)
• Lack of clear traumatic mechanism
• Constitutional symptoms
• Size >5 cm

Do Not Skip MRI When Ultrasound is Uncertain

Ultrasound assessment is highly user-dependent 1. When the radiologist expresses any uncertainty, MRI must be performed rather than relying on clinical follow-up alone. 1

Supporting Research Evidence

Research studies confirm the guideline recommendations: 4, 6, 7

• A 2009 study of 358 patients demonstrated that ultrasound correctly identified all benign lesions (284/284) with no missed malignancies on 24-30 month follow-up 4
• Ultrasound detected 77% of soft tissue sarcoma recurrences in post-treatment surveillance, compared to only 61.5% for CT 6
• Case reports demonstrate ultrasound's ability to characterize rare sarcoma subtypes when high-resolution technique and Doppler are employed 7