Immunohistochemical detection of ROS 1 is useful for identifying EGFR mutation in lung adenocarcinoma

초록

Abstract type: Original Abstract Title: Immunohistochemical detection of ROS1 is useful for identifying EGFR mutation in lung adenocarcinoma Abstract: Background and Aims; the low prevalence of ROS1 fusions, a significant proportion of ROS1 immunohistochemistry (IHC)-positive cases are ROS1 fusion-negative in patients with lung adenocarcinoma. We investigated the molecular characteristics of ROS1 immunohistochemically false-positive cases. <br /><br />Methods<br /><br />Thirty-six patients who were histologically diagnosed with lung adenocarcinoma at Inha University Hospital between 2018 and 2022 and were positive for ROS1 IHC were included. Epidermal growth factor receptor (EGFR) PCR, ALK IHC, BRAF IHC, and ROS1 fusion were investigated from biopsy samples of primary tumor at the time of diagnosis.<br /><br />Results<br /><br />ROS1 fusion was positive in only 3 out of 36 patients. Twenty-one (63.6%) of 33 patients were positive for EGFR PCR test, with exon 19 deletion in 6, L858R in 13, exon 20 insertion in 1, and G719X in 1. And a 1 patient was positive for BRAF V600E IHC. Next-generation sequencing will be analyzed on tissue samples of primary tumor from 12 patients who are ROS1 fusion-negative and EGFR PCRnegative.<br /><br />Conclusion<br /><br />The significant proportion of ROS1 IHC-positive and ROS1 fusionnegative patients showed positive for EGFR PCR tests. This finding suggests that clinicians should pay attention to EGFR PCR tests in ROS1 IHC-positive patients. Keywords: ROS1, immunohistochemistry, EGFR