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P2.09 - Pathology (ID 174)
- Event: WCLC 2019
- Type: Poster Viewing in the Exhibit Hall
- Track: Pathology
- Presentations: 1
- Coordinates: 9/09/2019, 10:15 - 18:15, Exhibit Hall
P2.09-27 - Correlation Between Different ROS1 Clones (SP384 & D4D6) and Consistency with ROS1 Fluorescence in Situ Hybridization (FISH) Results (ID 2394)
10:15 - 18:15 | Author(s): Onur Dulger
Since treatment options for ROS1 translocated Non-Small Cell Cancer cases has been revealed, ROS1 testing was included in NSCLC guidelines. FISH method is essential for the detection of these cases. Immunohistochemically ROS1 testing in the guidelines is recommended as an aid to the FISH method. The most commonly used commercial ROS1 clone is D4D6. Recently a new immunohistochemical (IHC) clone which has higher sensitivity and specificity (SP384) is available. The aim of this study is to compare these ROS1 antibodies and to interpret with FISH results.Method
Twenty-three patients (fourteen ROS1 FISH-positive, nine ROS1 FISH-negative) were included for this study. The material available for all tumors had been formalin-fixed and paraffin-embedded (FFPE). D4D6 clone from Cell Signaling Technology and SP384 clone were provided by Ventana Medical Systems, which were used for ROS1 expression. The staining study was performed according to previously published methodology. ROS1 expression was evaluated by intensity scoring. IHC staining patterns of tumor cells was also interpreted as cytoplasmic or membranous and/or both pattern predominantly.
All samples of FISH testing has been performed with LSI ROS1 Break Apart Probe; Abbott Molecular probe.
Incompatible cases according to FISH and IHC results AmoyDx gene fusions detection kit testing has been used as confirmatory RT-PCR method.Result
Table 1. The immunhistochemical and FISH results of the cases
Staining Pattern Tumor Cell Staining Pattern D4D6
Staining Pattern Tumor Cell Staining Pattern FISH
Cy. Mb. Cy. Mb. 1 2 heterogeneous + + 1 heterogeneous + + b.a*. 2 3 heterogeneous + + 1 heterogeneous + - b.a*. 3 2 heterogeneous + - 1 heterogeneous + - b.a*. 4 3 homogeneous + - 2 homogeneous + - iso 3' 5 3 heterogeneous + - 1 homogeneous + - iso 3' 6 2 heterogeneous + + 1 heterogeneous + - b.a*. 7 3 homogeneous + - 2 homogeneous + - iso 3'** 8 - - - - - - - - n*** 9 3 homogeneous + + 2 heterogeneous + - b.a*. 10 3 homogeneous + + 2 homogeneous + + b.a*. 11 3 homogeneous + - 1 homogeneous + - b.a*. 12 3 homogeneous + + 1 homogeneous + - b.a*. 13 3 heterogeneous + - 1 heterogeneous + - b.a*. 14 3 homogeneous + - 2 homogeneous + - b.a*. 15 3 homogeneous + - 2 homogeneous + - iso 3' 16 - - - - - - - - n*** 17 - - - - - - - - n*** 18 - - - - - - - - n*** 19 - - - - - - - - n*** 20 3 homogeneous + - - - - - n*** 21 - - - - 2 homogeneous + - n*** 22 1 heterogeneous + + 2 heterogeneous + + n*** 23 3 homogeneous + + 3 homogeneous - + n***
*Break apart, **İsolated 3', *** Negative
-The immunhistochemical and FISH results of the cases are presented on Table1.
-The study included 14 FISH positive, 6 FISH negative and 3 incompatible cases by FISH and IHC results
-All ROS1 FISH rearrenged cases were also positive for both D4D6 and SP384 clones but the intensity was mostly higher; SP384 showed almost always higher intensity except in two cases (case22 and 23).
-Incompatible 3 cases (Case 20, 21 and 23) FISH results were confirmed by RT-PCR but IHC results were variable.
-Break apart pattern FISH positive cases did not showed membranous staining in both immunhistochemstry clonesConclusion
-ROS1 SP384 is more feasible then D4D6 for ROS1 protein evaluation. However, both clones may rarely be incompatible with FISH results.
-We recommend that the IHC and FISH study should be done together.
-In incompatible cases, the RT-PCR study will be determinant with the FISH study.