Presentation
Right foot dorsum nodular lesion on fibular aspect near 5th metatarsal base for a few months.
Patient Data
Well-defined soft tissue lesion is seen in region of interest. Size - 19 x 12 x 10 mm
Location - Abutting peroneus longus tendon. Lesion encircles more than 180 but less than 360 degree of tendon. Separate from bone and tendon.
Dynamic scan - Free movement of the tendon was noted from the lesion.
Morphology - Solid - Multiple tiny echogenic foci. Large lobulation present.
Doppler - Arterial as well as venous flow noted. Flow within the lesion and in the wall.
No focal osseous lesion. No soft tissue calcification.
Case Discussion
Most of the foot masses are benign tumors or tumor-like conditions. Differentials include: ganglion, bursitis, foreign body granuloma, pigmented villonodular synovitis, giant cell tumor of tendon sheath, hemangioma.
Two malignant lesions should be included - Synovial sarcoma and malignant melanoma.
After US scanning, two possibilities were reported:
- Giant cell tumor of tendon sheath because the lesion is nearly encircling peroneus tendon.
- Hemangioma due to high vascularity and some echogenic foci - ? calcification.
A radiograph was done after the US, to check for calcification, but it could not be seen.
The lesion was removed after 3 days. Surgeon discarded the possibility of hemangioma on gross examination.
The first biopsy report was suspicious for malignancy. Further evaluation of the slide was done by immunohistochemistry.
Final biopsy diagnosis - synovial sarcoma.
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