Screening for NTRK-rearranged Tumors Using Immunohistochemistry: Comparison of 2 Different pan-TRK Clones in Melanoma Samples.

NTRK-rearranged tumors could be treated using promising anti-TRK-targeted therapies in patients with advanced cancers including melanomas. Different targeted therapies are being developed together with different screening strategies including pan-TRK immunohistochemistry (IHC) as first-line screening strategies. In this technical study, we compared 2 pan-TRK IHC (using A7H6R and EPR17341 clones) in tumor samples of patients with advanced melanomas. IHC-positive cases were studied using NTRK1, NTRK2, and NTRK3 fluorescent in situ hybridization tests. Among 300 melanoma samples, 4 samples were positive using A7H6R IHC, but none using EPR17341. None of the 4 samples were NTRK-rearranged using fluorescent in situ hybridization. Different staining was also noted in nontumor kidney tissue, whereas an NTRK1-rearranged tumor used as positive control was strongly stained with both A7H6R and EPR17341 clones. Future studies including more numerous NTRK-rearranged tumors are required to further study and compare the performances of different pan-TRK clones in the screening of NTRK-rearranged cancers.