Imaging Approach for Soft Tissue Lumps of the Foot

Initial Imaging Approach

The American College of Radiology recommends plain radiographs as the first step for any new soft tissue mass of the foot to identify bone involvement, calcifications, or radio-opaque foreign bodies 3, 4
Radiographs can identify bone abnormalities, deformities, and mineralization patterns, but have limited sensitivity (54%) and specificity (68%) for soft tissue masses 5
The Journal of the American College of Radiology suggests that radiographs may be unrewarding when a mass is small, deep-seated, non-mineralized, or in areas with complex anatomy such as the deep soft tissues of the feet 4
Ultrasound should be used as the primary triage tool after radiographs for evaluating soft tissue masses of the foot, with high sensitivity (94.1%) and specificity (99.7%) for superficial soft tissue masses 1, 2, 3

The British Journal of Cancer recommends MRI when ultrasound findings are uncertain, when clinical concern persists, or for deep-seated masses 1, 2
MRI provides the most accurate information for diagnosis and surgical planning for soft tissue tumors affecting the extremities, including the foot 2
CT is not typically ordered for the initial evaluation of a soft tissue mass of the foot, but can be useful in specific situations where complex osseous anatomy needs evaluation or when precise characterization of mineralization patterns is required 3, 4

For deep soft tissue masses of the foot, MRI is strongly recommended after initial radiographs 2, 4
If there are concerning features on ultrasound suggestive of soft tissue sarcoma, an urgent referral for MRI should be made within 2 weeks 1

Ultrasound assessment is highly user-dependent, which may affect diagnostic accuracy 2
Relying solely on radiographs may miss significant soft tissue pathology due to their limited sensitivity for soft tissue masses 5
Assuming that all soft tissue masses of the foot are benign can lead to delayed diagnosis of malignancy; any mass that is not clearly a cyst on ultrasound warrants further evaluation 1, 2