Synovial sarcomas of three children in the first decade: clinicopathological and molecular findings

Synovial sarcoma in children below the age of 10 years is rare. We report on three cases of synovial sarcoma which were diagnosed in three children aged 3, 8 and 8 years, respectively. These tumors were located in the hip of the 8-year-old, the foot of the 3-year-old, and the elbow of the other 8-year-old. Histologically, one tumor was a biphasic synovial sarcoma, and the other two, which had been initially diagnosed as infantile fibrosarcoma, were of the monophasic fibrous type. In the three cases, a reverse transcription-polymerase chain reaction (RT-PCR) using ribonucleic acid extracted from formalin-fixed, paraffin-embedded tissues detected SYT-SSX1 fusion gene transcripts resulting from translocation t(X;18)(p11.2;q11.2), which is specific for synovial sarcoma. ETV6-NTRK3 fusion gene transcripts that result from t(12;15)(p13;q25), which is characteristic of congenital/infantile fibrosarcoma, were not demonstrated. In conclusion, other pediatric soft tissue sarcomas, such as congenital/infantile fibrosarcoma, spindle cell rhabdomyosarcoma, leiomyosarcoma and malignant peripheral nerve sheath tumor, should be distinguished from synovial sarcoma in children, especially the monophasic fibrous type. RT-PCR analysis is a useful approach to the final diagnosis of synovial sarcoma arising at such an early age.