ROS1 Targeted Therapy Test - Immunohistochemistry (IHC) for ROS1

Immunohistochemical (IHC) or molecular assays are used to detect the ROS1 protein (c-ros oncogene 1), particularly in cases of ROS1 gene rearrangement. ROS1 gene rearrangement is an epigenetic (acquired) mutation that results in its fusion with other genes (such as CD74 and SLC34A2), producing a mutated protein that independently promotes cancer growth. This assay is a key prognostic marker for response to ROS1 kinase inhibitors in non-small cell lung cancer.