ALK and ROS1 testing on lung cancer cytologic samples: Perspectives

Abstract

Cytologic sampling is the mainstay of diagnosing advanced lung cancer. Moreover, to select patients for personalized first-line or second-line treatment, epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) and c-ros oncogene 1 (ROS1) rearrangements are tested on cytologic preparations. Commercially available fluorescence in situ hybridization (FISH) and immunocytochemistry (ICC) assays have primarily been used for the identification of cells harboring ALK or ROS1 gene fusions on histologic rather than cytologic preparations. However, it is now recognized that FISH and ICC also can be applied on cytologic samples provided the cytopathologist is aware that FISH and ICC results are not always concordant and that the performance of ICC largely depends on antibody clones, signal detection systems, and scoring systems. Notably, the routine clinical use of FISH and ICC may be replaced by emerging next-generation sequencing and digital, color-coded barcode technologies, which have the advantage of simultaneously evaluating ALK, ROS1, and EGFR alterations in a single analysis. Although their use in clinical cytologic practice remains to be fully established, it is conceivable that this technology will replace both FISH and ICC analyses in future diagnostic algorithms. Here, the authors review studies devoted to testing ALK and ROS1 on cytology specimens in an attempt to provide an update for the cytopathologist regarding current and evolving practice. Cancer Cytopathol 2017;125:817-30. © 2017 American Cancer Society.

PD-L1 expression on routine samples of non-small cell lung cancer: results and critical issues from a 1-year experience of a centralised laboratory

“…Thus, the crucial role of cytopathologist who evaluates on-site the adequacy of aspirated material and triage part of the samples to prepare a CB, it cannot be overemphasised. A resulting advantage lies in the possibility to use CB also for the evaluation of the overexpression of other relevant biomarkers, such as ALK and ROS1 30. Conversely, PD-L1 testing on direct smear should be performed only in the absence of an FFPE specimen and should be only carried out by laboratories with specific expertise 31–33.…”

Cell block cellularity: A comparison of two fixatives and their impact on cellularity

“…Based on our findings, it appears that formalin fixation is superior to CytoLyt processing in obtaining adequate and high cellularity specimens for molecular testing. While material from direct smears has been shown to be equal if not superior to cell block material for molecular testing, we have found cell block preparations may have an advantage over direct smears because replicate sections could be cut negating the sacrifice of diagnostic material.…”

“…Successful molecular testing requires a minimum amount of extractable DNA from cancer cells. A wide variety of specimen types including direct smears, liquid‐based cytology specimens, and cell block material have been shown to be useful for molecular testing, but all are associated with a limited amount of material for such testing . Cell block material has been shown to be an excellent substrate for immunohistochemical testing but also can be used for molecular testing including PCR techniques and next generation sequencing .…”

A practical guide for ancillary studies in pulmonary cytologic specimens

“…ROS1 translocations are rare events in adenocarcinomas (approximately 1%), but ROS1 mutation testing is strongly recommended . It is currently recommended that ROS1 immunohistochemistry be performed for screening; however, positive immunohistochemistry needs to be confirmed by molecular or cytogenetic testing …”