It is uncommon to see aggressive tumors in the foot. Most of the soft tissue masses are generally ganglions, rheumatoid nodules, lipomas, synovial cysts and fibromas. X-ray examination is routine for all soft tissue masses and when there is bone destruction from a soft tissue mass, things get a little interesting. Generally speaking, bone destruction is not good. Both malignant and benign tumors can destroy bone.
I have an interesting case to share. A 36-year-old male presented to my office with the chief compliant of a minimally painful lump on the bottom of his big toe. He thought he broke the toe as a teenager playing sports and it just never “healed right.” The mass under the toe was getting so large that wearing shoes was getting difficult but pressure to the mass did not cause any pain.
His past medical history was unremarkable. He was not taking any medication on a regular basis. He had prior shoulder surgery. He denied smoking or alcohol use. At the time, he was working in management for a computer chip manufacturer.
The physical exam revealed a well dressed, well nourished male in good physical condition. His neurovascular exam was within normal limits. The dermatologic exam revealed a firm, non-fluctuant mass on the plantar and lateral aspect of the great toe. There was no break in the integument. The skin showed no color changes. The orthopedic exam revealed a pes cavus foot type.
Plain film radiographs showed a well circumscribed lytic bone lesion in the proximal phalanx. The cortex was intact and it did not extend into a joint. Magnetic resonance images were remarkable for a soft tissue mass measuring 3.3 cm x 2.2 cm x 1.6 cm. The mass was dark on both T1 and T2, which suggested a fibrous origin. Minimal enhancement with contrast was present. The radiologist reported that a malignant fibrous histiocytoma would rank high in the differential diagnosis.
I obtained a biopsy of the mass prior to definitive surgery and it turned out to be a giant cell tumor of tendon sheath.
I planned surgery for excision of the soft tissue mass and curettage of the bone cyst with grafting. After removing a cortical window on the dorsal aspect of the proximal phalanx and removing the intra-osseous aspect of the tumor, I was staring down to the flexor tendon as the mass had completely destroyed the plantar cortex.
After curetting the bone cyst, I lifted the cortical bone and placed it into the “hole,” which acted as the floor or plantar cortex. Since the window was rectangular and the plantar hole was round, there was no fear of the “floor” falling through. I packed the rest of the defect with bone graft material.
The patient’s postoperative course was uneventful. I lost him to follow-up as he moved to Florida for a job transfer.
Giant cell tumors of tendon sheath are benign, peritendinous soft tissue masses that often have aggressive features of bone erosion. Microscopically, there are multinucleated giant cells, histiocytes, macrophages and osteoclast-like cells that most likely contribute to the tendency for bone erosion.
I recommend biopsy prior to definitive resection of any soft tissue mass of uncertain etiology. Certainly if the mass turns out to be malignant, the medical and surgical management would be drastically different. Rather than excising the mass and obtaining a frozen section (which would then dictate your surgical plan), you can predetermine a definitive plan for the patient.