What is the appropriate workup for a mass found on the arm?

Appropriate Workup for a Mass Found on the Arm

The initial imaging study for a soft tissue mass on the arm should be radiographs, with ultrasound being equally appropriate for small lesions that are superficial to the deep fascia. 1

Initial Evaluation

First-Line Imaging

• Radiographs: Despite often being considered unrewarding, radiographs demonstrate positive results in 62% of cases with proven soft-tissue masses 1

  • Can identify calcification (27% of cases), bone involvement (22%), and intrinsic fat (11%)
  • May be diagnostic for specific conditions like phleboliths in hemangiomas or peripheral ossification of myositis ossificans

• Ultrasound: Particularly useful for small superficial lesions 1, 2

  • High accuracy for superficial soft-tissue masses (sensitivity 94.1%, specificity 99.7%)
  • Most accurate for lipomas, followed by vascular malformations, epidermoid cysts, and nerve sheath tumors
  • Helps differentiate solid from cystic lesions and localized masses from diffuse edema

Risk Assessment

Consider concerning features that may indicate malignancy 2:

• Mass size >5 cm
• Deep-seated location (beneath fascia)
• Increasing size over time
• Pain associated with the mass
• Patient age >50 years

Secondary Evaluation

If initial imaging is non-diagnostic or concerning features are present:

MRI

• Gold standard for further evaluation of soft tissue masses 1, 2
• MRI without and with IV contrast is usually appropriate for non-diagnostic initial evaluations
• Provides superior tissue characterization and anatomic detail
• Particularly valuable for deep-seated masses or masses with atypical features

CT Scan

• Consider when 1, 2:
  • Patient is non-MRI compatible
  • Metal is limiting MRI evaluation
  • There's concern for bone involvement or calcifications
  • The mass is suspected to be retroperitoneal with extension to the extremity

Biopsy

• Core needle biopsy is the standard approach if malignancy is suspected after initial imaging 2
• Biopsy route must be carefully planned with the surgeon to ensure the tract can be excised during definitive surgery
• Should be performed at the facility that will provide definitive management

Special Considerations

For Vascular Masses

• If spontaneous hemorrhage or vascular mass is suspected, MRI without and with IV contrast or CT without and with IV contrast is appropriate 1

For Superficial Lesions

• Ultrasound may be sufficient for definitive diagnosis of certain lesions (simple cysts, lipomas, vascular malformations) 1, 3
• Consider anatomic location - lesions may arise from the epidermis/dermis, within subcutaneous adipose tissue, or in association with fascia 3

Follow-up Management

• If the mass is definitively characterized as benign, clinical follow-up is appropriate 1, 2
• Regular clinical monitoring every 6-12 months is recommended if managed conservatively 2
• Patient education on when to return sooner (growth, increased pain, changes in appearance) is essential 2
• For suspicious masses, wide surgical excision with negative margins is necessary 2

Common Pitfalls to Avoid

1. Relying solely on physical examination for diagnosis (only 85% of lipomas are correctly identified by physical examination alone) 1

2. Failing to perform appropriate imaging before biopsy, which may lead to suboptimal biopsy planning 1, 2

3. Not considering the patient's age in the diagnostic approach (higher risk of malignancy in patients >50 years) 2, 4

4. Overlooking the need for a complete staging workup before intervention if malignancy is suspected 2

5. Initiating physical therapy before establishing a definitive diagnosis, which could delay proper treatment of a malignancy 2