Maureen O’Sullivan1,2 *, Tony Ng1 *, Torsten Nielsen1, Malcolm Hayes1,3, Paul Clarkson4, Catherine Pallen5, Poul Sorensen1,6, Doug Horsman1,3

1 Department of Pathology and Laboratory Medicine, University of British Columbia, 2 Division of Anatomic Pathology, British Columbia’s Children’s Hospital,

3 Department of Pathology and Laboratory Medicine, British Columbia Cancer Agency, 4 Department of Surgery, UBC

5 Department of Pediatrics, Child and Family Research Institute, UBC,6 Department of Molecular Oncology, British Columbia Cancer Research Centre, Vancouver, Canada

*These authors contributed equally

Novel translocation t(2;16)(q35;p11) producing an in-frame fusion of FUS and FEV in a Ewing

sarcoma lacking EWS rearrangement

Molecular Pathology of Ewing Family Tumours

• Ancillary diagnostic and potentially prognostic value• Typically, EWS (member of TET family) rearranged

with any one of a number of Ets family members: Fli1, Erg, ETV1, ETV4, FEV.

• Recent report of additional TET family member FUS rearranged with Erg in 4 cases of EFT.

Case History

• 33 year-old man sustains pathologic fracture while snowboarding

• Plain film images show moth-eaten distal clavicle• Incisional biopsy inadequate, but with suspicious

population of small blue cells• Excisional biopsy = EFT• Patient treated with 11 courses of chemo,

irradiation and then surgical excision = negative margins and 100% tumour kill.

Pathology

Cytogenetics

t(2;16)(q35;p11)

FISH with FUS Break-apart Probe

FISH with BAC RP11-207M4

RT-PCR, Cloning and Sequencing

• Primers : Forward - FUS exon 1; Reverse - FEV exon 3

• Product of 1.4Kb on electrophoresis

• Cloned and sequenced

RT-PCR, cloning and sequencing

FEV Exon 2 FUS Exon 10

In-frame FUS exon 10 to FEV exon 2 fusion

• Novel Translocation

• Another example of a translocation in EFT involving FUS

• New FUS breakpoint

FUS, FEV Breakpoints – modified from Janknecht; Gene 2005

EWS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

SYQG activation domain RGG-rich RNA-binding RGG-rich Zn RGG-rich

FUS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

SYQG activation domain RGG-rich RNA-binding RGG Zn RGG-rich

FUS-FEV

FEV

1 2 3

DNA-binding Ala-rich

FLI-1 1 2 3 4 5 6 7 8 9

Pointed domain DNA-binding Pro-rich

ERG

Pointed domain DNA-binding Pro-rich

ETV1

AD DNA-binding Pro-rich

ETV4

AD DNA-binding Pro-rich

1 2 3 4 5 6 7 8 9 10 2 3

SYQG activation domain RGG-rich RNA-binding DNA-binding Ala-rich

?Further Evidence of FUS or FEV rearrangement in EFTs? – TMAs being

evaluated

Conclusion

• Novel Chromosomal Translocation t(2;16)(q35;p11) in Ewing sarcoma;

• Underscores the interchangeability of fusion partners in EFT translocations

• Consider FISH with FUS break-apart if EWS break-apart negative

3 weekly cycles, 11 in total, alternating 6 cycles of ifosfamide 9g/m2 etoposide 500mg/m2 given over 5 days

with 5 cycles of vincristine 2mg, doxorubicin 75mg/m2, cyclophosphamide 1g/m2 given on 1 day

local control commenced after 5 cycles with radiation, 45 Gy in 25 fractions (chemotherapy continued concurrently)

then 8 weeks post radiation surgery with resection of distal clavicle and surrounding tissues