What is the appropriate management for a patient with a soft tissue density structure found on radiological examination, considering their demographic and medical history?

Management of Soft Tissue Density Structure on Radiological Examination

Begin with plain radiographs of the affected area, followed immediately by ultrasound for characterization of any confirmed soft tissue mass, as this algorithmic approach provides the foundation for all subsequent management decisions. 1

Initial Imaging Algorithm

Step 1: Plain Radiographs

• Obtain radiographs first for any suspected soft tissue mass, as they identify intrinsic fat in 11% of cases, detect calcification in 27%, and reveal bone involvement in 22% of cases 1
• Radiographs may be diagnostic for specific entities including phleboliths within hemangiomas, osteocartilaginous masses, or peripherally mature ossification of myositis ossificans 2
• Recognize that radiographs may be unrewarding for small, deep-seated, or non-mineralized lesions 1

Step 2: Ultrasound Evaluation

• Proceed to ultrasound as the most useful initial characterization tool, with 94.1% sensitivity and 99.7% specificity for superficial soft tissue masses 1
• Assess for benign features: hyperechoic or isoechoic appearance compared to surrounding fat, well-circumscribed margins, thin curved echogenic lines, and minimal to no internal vascularity on Doppler 1, 3

Red Flags Requiring Advanced Imaging

Obtain MRI without and with contrast if ANY of the following are present:

• Mass size >5 cm in diameter 1
• Deep-seated location (below the fascia) 1
• Heterogeneous echotexture on ultrasound 1
• Increased vascularity on Doppler examination 1
• Irregular or poorly defined margins 1
• Rapid growth or change in size 1
• Pain or tenderness 1
• Deep location in the lower limb (heightened concern for atypical lipomatous tumor) 3

Critical caveat: Ultrasound is considerably less accurate for deep masses compared to superficial ones, so maintain a lower threshold for MRI in deep-seated lesions 1

Tissue Diagnosis

Perform core needle biopsy (preferably ultrasound-guided) for:

• Any mass with suspicious features on imaging 1
• Masses that are symptomatic, rapidly growing, or >5 cm 1
• Deep-seated masses or those in the lower limb where atypical lipomatous tumor cannot be excluded 3

Core needle biopsy is superior to fine-needle aspiration for sensitivity, specificity, and correct histological grading 1

Management Based on Findings

For small (<5 cm), superficial, asymptomatic masses with typical benign imaging features:

• Observation with clinical follow-up at 6-12 months to assess for growth is appropriate 1
• Surgical excision is indicated if the mass becomes symptomatic, demonstrates rapid growth, or causes patient anxiety 1

For masses requiring intervention:

• Complete en bloc surgical excision is the standard treatment for symptomatic, rapidly growing, large (>5 cm), or atypical masses 1
• Wide excision or compartmental resection including the cutaneous scar and biopsy tract is required for confirmed sarcomas 2

Referral Criteria

Refer to orthopedic oncology or specialist sarcoma multidisciplinary team BEFORE performing biopsy if:

• Your institution is not equipped for definitive treatment 1
• Imaging is suggestive of soft tissue sarcoma 1
• There is diagnostic uncertainty regarding atypical lipomatous tumor versus lipoma 3

This is critical: Inappropriate biopsy technique or location can compromise subsequent definitive surgical management 2

Special Considerations for Post-Treatment Surveillance

In the post-radiation therapy setting:

• Deep ill-defined soft tissue abnormality without discrete mass but with differential enhancement or mild FDG uptake warrants shorter-interval follow-up (3 months) or immediate PET if only CECT was performed (NI-RADS 2b category) 2
• The majority (83%) of such abnormalities represent post-treatment change rather than recurrence, so biopsy should be avoided in most circumstances 2
• Focal mucosal enhancement or enhancement deep to an ulceration requires direct clinical inspection as the first management step (NI-RADS 2a category) 2

Critical Pitfalls to Avoid

• Do not rely on physical examination alone, as it correctly identifies only 85% of lipomas 1
• All deep-seated masses or those in the lower limb should raise concern for atypical lipomatous tumors, even if they appear benign on superficial assessment 1, 3
• Soft tissue sarcomas are rare (<1% of malignancies) but have high mortality rates, requiring urgent evaluation with MRI and potential referral to orthopedic oncology 1
• Image-guided biopsy is preferred over palpation-guided biopsy, allowing confirmation of biopsy accuracy and placement of a marker clip 1