Emile Sansakda-Phillips1, Emma-li Yit1, Fiona Webb1, Maya Latimer2,3, Adrienne Morey3,4, Dipti Talaulikar2,3
1 Cytogenetics department, The Canberra Hospital, PO Box 11, Woden, ACT, 2606
2 Haematology department, The Canberra Hospital, PO Box 11, Woden, ACT, 2606
3 The Australian National University, Acton, ACT, 2601
4 Anatomical Pathology department, The Canberra Hospital, PO Box 11, Woden, ACT, 2606
Background: Double hit lymphoma (DHL) is a subtype of diffuse large B-cell lymphoma (DLBCL) characterised by the presence of c-MYC and BCL2 and/or MYC and BCL6 gene rearrangements on Fluorescence in-situ Hybridisation (FISH). Double expressor lymphomas (DEL) are DLBCL cases with high expression of MYC and BCL2 proteins on immunohistochemistry (IHC). DHL and DEL are associated with a poor outcome with DEL being associated with a less adverse outcome.
Aims: Given the high cost of FISH testing to establish a diagnosis of DHL, and the lack of definitive guidelines for selecting cases for FISH, we conducted this study to determine whether c-MYC IHC could be used as a screening tool. Our second aim was to determine whether FISH analysis could be reliably performed on tissue sections.
Methods: Laboratory data on IHC and FISH tests performed on DLBCL (n=14) and Burkitt lymphoma (BL) (n=1) cases between 2015 and 2016 was extracted and analysed. A cut-off value of 40% was used to determine positivity on IHC for c-MYC. FISH studies were performed in-house (on fresh or Formalin Fixed Paraffin Embedded (FFPE) tissue sections) (n=13) or as sendaways (n=2).
Results: 7 cases of DLBCL were diagnosed to be DEL. Of these, the average expression was 67% for c-MYC. BCL2 expression was positive in 14 cases (quantitative data was not available). FISH for c-MYC was positive in 6 cases including one case of BL. FISH for BCL2 was positive in 8 cases with 3 cases being DHL and 1 THL. All 4 cases were DEL.
Overall, 11 cases were tested using FFPE tissue with reportable results obtained for all cases.
Conclusion: In our laboratory, c-MYC IHC appears to be a good screening tool and FPPE is a feasible method for FISH analysis for DHL. A more substantial data set is being curated to expand the cohort.
Scientists from the cytogenetics department in ACT Pathology, The Canberra Hospital