Late solitary bone metastasis of a primary pulmonary synovial sarcoma with SYT-SSX1 translocation type: case report with a long follow-up.

Primary synovial sarcoma outside its classical presentation in para-articular soft tissue of young patients is rare but regularly reported. One of the rarest primary locations is the lung. We describe a 73-year-old female patient who presented with a solitary malignant bone tumor 8 years after the resection of a lung neoplasm. The bone tumor was classified as an osteosarcoma and the lung tumor as an atypical carcinoid tumor at their first respective diagnostic work-ups. The resection of the affected humerus with allograft and endoprosthesis implantation followed. Reevaluation of the tumor samples at the time of the local recurrence of the bone tumor 6 years following the initial symptoms of the bone tumor lead to the reclassification of both specimens as synovial sarcomas. Both neoplasms contained the SYT-SSX1 type of the diagnostic translocation t(X;18) as detected by the reverse-transcription polymerase chain reaction analysis. The patient died 14 years after the resection of the primary synovial sarcoma of the lung and 6 years following the occurrence of the bone metastasis. This prolonged clinical course is uncommon for the SYT-SSX1 translocation, which, in other locations, is usually associated with an unfavorable prognosis.