What is the treatment approach for a soft tissue mass of the foot?

Treatment Approach for Soft Tissue Mass of the Foot

The treatment approach for a soft tissue mass of the foot should begin with radiographs as the initial imaging study, followed by ultrasound for superficial lesions or MRI for deep lesions, and then appropriate biopsy for definitive diagnosis before determining the final treatment plan. 1

Initial Evaluation

Imaging

• Radiographs should be the first imaging study for any suspected soft tissue mass of the foot to identify calcifications, bone involvement, or intrinsic fat 1
• Ultrasound is highly appropriate for small, superficial lesions (those above the deep fascia) with reported sensitivity of 94.1% and specificity of 99.7% for superficial soft tissue masses 1
• For deep masses or those in the complex anatomy of the foot, radiographs may be unrewarding and additional imaging is necessary 1

Advanced Imaging

• MRI without and with IV contrast is the preferred next step if initial evaluation is nondiagnostic, especially for deep masses of the foot 1, 2
• MRI provides the most accurate information for diagnosis and surgical/radiotherapy planning for soft tissue tumors affecting the extremities 1, 2
• MRI can accurately show the anatomic location and extent of foot tumors, which is critical for surgical planning 2

Diagnostic Procedures

Biopsy

• Percutaneous core needle biopsy is the standard approach to establish histopathological diagnosis of suspicious soft tissue masses 1

  • Multiple cores should be taken under image guidance to maximize diagnostic yield
  • The biopsy should be planned so the tract can be safely removed during definitive surgery

• Excisional biopsy may be the most practical option for:

  • Small subcutaneous lesions that are indeterminate on imaging (<2 cm diameter) 1
  • Superficial lesions <5 cm 1

• Open biopsy may be considered in selected cases after discussion with a multidisciplinary team 1, 3

Treatment Planning

Benign Lesions

• Most soft tissue masses of the foot are benign (common examples include lipomas, ganglion cysts, fibromatosis, and hemangiomas) 4, 5
• Benign lesions may be:
  • Observed if asymptomatic and diagnosis is certain 6
  • Excised if painful, growing, or cosmetically concerning 6

Malignant Lesions

• For suspected sarcomas, referral to a specialized sarcoma center with a multidisciplinary team is mandatory 1
• Treatment typically involves:
  • Wide excision or compartmental resection 1
  • Adjuvant radiation therapy for high-grade sarcomas after wide excision 1
  • Consideration of chemotherapy in specific cases 1

Special Considerations for Foot Masses

• The foot contains relatively little soft tissue but is rich in tendons, fasciae, and synovium, making certain lesions more common (giant cell tumor of tendon sheath, fibromatosis, vascular tumors) 4
• MRI often shows distinctive features for certain benign foot lesions:
  • Hemangiomas: high T2-weighted intensity and internal septa 2
  • Ganglion cysts: homogeneous, high T2-weighted intensity and peritendinous location 2
  • Plantar fibromatosis: nodularity of plantar aponeurosis with low intensity on all sequences 2

Warning Signs Requiring Urgent Evaluation

• Masses that are deep to the fascia 6
• Masses that are 5 cm in diameter or larger 6
• Masses that grow rapidly or present suddenly without explanation 6
• Masses with concerning imaging features should be referred to specialized sarcoma centers 1

Follow-up

• For patients with high-grade tumors, regular follow-up is recommended:
  • Every 3 months with history and physical examination 1
  • MRI of the resection site twice a year for the first 2-3 years, then annually 1
  • Chest X-ray every 3-4 months in the first 2-3 years for high-grade tumors 1