A case of lung adenocarcinoma with a novel CD74-ROS1 fusion variant identified by comprehensive genomic profiling that responded to crizotinib and entrectinib.

ROS1 rearrangements are found in 1-2% of patients with non-small-cell lung cancer. The detection of the rearrangements is crucial since clinically effective molecular targeted drugs are available for them. We present a case of lung adenocarcinoma with a previously unknown ROS1-CD74 fusion variant, CD74 exon 3 fused to ROS1 exon 34, which was not detected by a conventional RT-PCR-based test for ROS1 fusion gene detection but identified by hybrid capture-based next-generation sequencing. This tumor responded to crizotinib initially and to entrectinib after relapse with brain metastasis, indicating the oncogenic activity of this novel fusion variant.