[Detection of ALK and ROS1 rearrangements by immunocytochemistry on cytological samples]

The identification of ALK and ROS1 rearrangements has become essential for the theranostic management of patients with non-small cell lung cancer, especially in stage IV or inoperable patients. These testings are now performed by immunohistochemistry on histological samples and confirmed by fluorescent in situ hybridization in case of positive or doubtful results. The diagnosis of lung cancer is often performed at an advanced or metastatic stage and cytological sample could be the only material containing malignant cells available at these stages. Therefore, the detection of ALK and ROS1 rearrangement by immunocytochemical analysis on cytological specimens is needed. We performed this test on 27 cytological samples of lung adenocarcinomas, and we compared our results with several other techniques: on the same sample or on biopsy in another laboratory, on the same sample by fluorescent in situ hybridization and/or immunochemistry. We found a very good concordance between all these techniques, thus validating our immunocytochemical method on cytological samples according to the ISO 15189 norm.