A case of an extremely calcified synovial Sarcoma

Clinical History

We present a clinical case of a 48-year-old man who complained of pain and swelling of a soft tissue mass in the foot with one year of evolution.

Imaging Findings

We performed an X-Ray and found an extremely calcified lesion in the plantar foot (Figure 1).
Scintigraphy showed an increased uptake of the radiotracer (Figure 2).
CT demonstrated a heterogeneous soft-tissue mass showing areas of enhancement and also calcifications (Figure 3 and 4).
T1 MRI-weighted images showed a prominently heterogeneous soft-tissue mass (Figure 5), while T2-weighted images identified areas of hight intensity signal (Figure 6). With MRI intravenous contrast a heterogeneous enhancement was evident (Figure 7).
Biopsy guided by CT to the more calcified component was performed (Figure 8).

Discussion

Synovial sarcoma is an aggressive soft tissue tumour that can occur at any age but most frequently between 15-40 years old [1]. It has a similar incidence in male and female gender [2] and represents about 10% of all soft-tissue sarcomas [3].
It does not seam to have a synovial origin. In fact, it has epithelial markers and only a small number of cases originate within a joint, with the majority of these tumours taking place adjacent to a joint [4]. Although it affects any part of the body, it occurs most commonly in the inferior limbs, with an increased prevalence in the popliteal fossa.

It usually presents as a mass that is noted by the patient. Most of the times, it is very indolent and has a slow growth rate. Nonetheless, it is a high-grade tumour with a considerable number of local recurrence and distant metastasis, mostly in the lung [2].

X-ray, CT and ultrasound can play an important role in characterizing this lesions, specially due to their great accuracy to detect the calcifications that are present in 30% of al cases [5]. Calcifications in rare cases, as in the one we report, can have extensive osteoid mineralization[5]. Around 11-20% of the patients have erosion of the bone or periosteal reaction [1], which can be detected in CT and X-Ray. However MRI is the gold standard not only for the diagnosis, but also for planning the surgery.
On MRI, the lesion can manifest as a heterogeneous mass mostly due to hemorrhage, necrosis, calcified and fibrotic tissue.
After the contrast injection the lesion usually shows enhancement [1] which can be evaluated both on CT and MRI.
Biopsy allows diagnostic to be made. Biopsy to the more superficial soft tissue component was primarily guided by ultrasound but, due to the fact that the pathological anatomy was inconclusive, we than performed biopsy of the more calcified component guided by CT.

Surgery for excision of the mass is currently the Gold standard treatment. However, when free margens are not achieved, than amputation should be considered [1]. Adjuvant therapie play an importante role when it comes to treatment: chemotherapy should be an option for the metastatic or residual disease, and radiation therapy, on the other side, can be important in two situations: previously to surgery, when one thinks negative margins will not be achieved or, after surgery, when one comes across positive margins [1].

Differential Diagnosis List

Final Diagnosis

Synovial sarcoma

URL:	https://www.eurorad.org/case/14222
DOI:	10.1594/EURORAD/CASE.14222
ISSN:	1563-4086