Extraskeletal myxoid chondrosarcoma with a t(9;16)(q22;p11.2) resulting in a NR4A3-FUS fusion.

Extraskeletal myxoid chondrosarcoma (EMC) is a rare neoplasm characterized by rearrangement of NR4A3. A t(9;22)(q22;q12), creating a fusion protein of EWSR1 and NR4A3, has been reported as a unique, recurring translocation in most cases. Reported variant translocations have resulted in fusion of NR4A3 with three other genes: TAF15, TCF12, and TFG. We report a case of EMC in a 59-year-old man who presented with a 6-month history of an enlarging mass in the proximal right thigh. The karyotype of fresh tissue from tumor taken at incisional biopsy revealed a t(9;16)(q22;p11.2). There was no evidence of an EWSR1 rearrangement by dual-color break-apart fluorescence in situ hybridization (FISH). Dual-color FISH probes revealed fusion of NR4A3 and FUS, a member of the TET family of genes, which includes EWSR1 and TAF15. Break-apart FISH probe results confirmed rearrangement of FUS. These findings show that a fusion product of FUS and NR4A3 may be an additional pathway to development of EMC.