Synovial sarcoma of the spinal canal and paraspinal muscle and retroperitoneum: a case with extensive calcification.

Synovial sarcoma (SS) is a rare mesenchymal malignant tumor. SS of the spine or retroperitoneum is an extremely rare site. Approximately 30% cases show focal calcifications on radiographs and computed tomography (CT) images, while extensive calcification rarely occurs. We presented a case of SS involving the spinal canal and paraspinal muscle and retroperitoneum, which showed extensive calcification on CT. The present report describes the case of a 13-year-old girl suffering from a tumor in the spinal canal and paraspinal muscle and retroperitoneum with extensive calcification on CT. The patient underwent lumbar and retroperitoneal giant tumor resection, lumbar decompression, and spinal tumor resection with a small tumor remnant remaining in the paravertebral region. Histological examination and genetic testing after surgery confirmed synovial sarcoma. After surgery, the patient refused local radiotherapy but agreed to receive chemotherapy. After 4 months of follow-up, her condition was basically stable, and the pain in her left lower limb disappeared. The residual tumor was not increased. Extensive calcification of SS is rare. The possibility of synovial sarcoma should be considered in those who show extensive calcification in the spinal canal and paraspinal muscle and retroperitoneum on CT. For cases that cannot be completely resected, adjuvant chemotherapy can control the residual tumor in the short term. In addition, the long-term effects need to be observed.