Physician’s Beware: MRI Inadequate for Synovial Sarcoma

In this case presentation, surgeons show how repeated MRIs did NOT reveal a malignant soft-tissue tumor later diagnosed as synovial sarcoma. As a result, an accurate diagnosis and appropriate treatment were delayed by a full year for the patient in question.

This young man (a 17-year-old high school football player) started having pain on the bottom of his left big toe (first metatarsophalangeal joint). The pain started after someone stepped on his forefoot during football practice. There were no other remarkable symptoms or problems, no observed or felt masses, and no evidence of infection, fracture, or tumor.

Even so, there was a rare malignant soft tissue tumor that was eventually discovered. The pathway to that discovery was lengthy and involved multiple steps of conservative (nonoperative) care. Because the first MRI showed a partial plantar plate disruption, a diagnosis of turf toe was made and confirmed with a second opinion. Treatment then consisted of antiinflammatories and physical therapy.

When the patient did not improve, a one-month trial of nonweight bearing in a cast was tried. The treatment worked and the pain went away but as soon as the young man went back to his regular activities (including sports and marching band), the pain was back. He was referred to a larger medical facility and evaluated by a fellowship-trained foot and ankle surgeon. X-rays and MRIs were repeated. Bone scans were ordered. It still looked like he had an unhealed, but stable, partial plantar plate disruption.

In the end, it was decided to do surgery to repair the plate injury. And that is when the true cause of the problem was fully appreciated. When the surgeon made an incision he found a firm, gritty, brown mass. It was removed and sent to pathology where the diagnosis of synovial sarcoma was made by viewing the cells under a microscope. With this information, a full metastatic scan was performed with no evidence of spread elsewhere.

The surgeon removed the first and second toe in order to get all of the cancer. The pathologist confirmed there were wide margins, meaning a sufficient area of healthy, normal cells around the cancer cells. The young man was given a special custom-made shoe insert (called an orthosis) to help him walk normally.

It was a long wait from that first injury to the correct diagnosis and another year before he was back to full activities. The prognosis was good given his young age (younger than 25 years), the small size of the tumor (less than one centimeter), and lack of metastasis (cancer had not spread). Follow-up chemotherapy and radiation were not required because of these three factors (age, tumor size, no mets).

Looking back on this case, the authors offer the following comments. First, it was no surprise that X-rays were negative. This type of (radiographic) imaging does not show soft tissue malignancies. However, it was unusual that the more advanced imaging (MRI) did not at least show some change in intensity to indicate a mass of this type.

Second, they suggested that it was the tumor that weakened the anatomic structures of the foot (e.g., sesamoid complex under the big toe). Then getting stepped on was enough force to cause further disruption and the resulting pain. The malignancy may have prevented his body from creating a normal inflammatory response to repair the problem. That’s why his symptoms persisted for so long.

The authors encourage physicians to consider synovial sarcoma when a patient presents with what looks like turf toe but has unusual patient history and lack of response to treatment. Reports like this help point out that a normal reading on an MRI can be misleading.

In summary, synovial sarcomas are rare but occur most often in young, healthy adults. They are often overlooked and/or mistaken for other problems. The authors found 25 other cases reported of synovial sarcoma of the forefoot, so it may occur more often than anyone previously realized.