Dahl Chase Folders

FISH for ROS1 Gene Rearrangements

Reference Number: AA-00437

ROS1 (6q22) Gene Rearrangement

Clinical Significance:

Recently established guidelines from the American Society for Clinical Pathology (ASCP), College of American Pathologists (CAP), Association for Molecular Pathology (AMP), and/or the American Society of Clinical Oncology (ASCP) recommend testing for all newly diagnosed non-small cell, non-squamous lung carcinomas or such metastatic lung carcinomas that have not had a primary resection available for testing. ROS1 (6q22) gene rearrangements can be found in 1-2% of non-small cell lung carcinomas (NSCLC), more commonly in adenocarcinomas of never or light smokers, whose tumors lack EGFR and KRAS mutations.  ROS1 gene rearrangement with common fusion partners include: CD74, SLC34A2, CCDC6, and FIG, and are associated with responsiveness to oral ROS1 tyrosine kinase inhibitors (TKIs).

Specimen Requirements and Collection:

Formalin fixed tissue containing a sufficient amount of tumor (generally at least several mm of tumor tissue submitted in the tissue block). 


Fluorescent in-situ hybridization (FISH)


Molecular pathology requisition form


Send formalin-fixed, paraffin-embedded (FFPE) tissue and cell block containing tumor at room temperature.  Also acceptable 10-unstained, 4-5 micron slides with 1 post H&E.  Please include a surgical pathology report

Unacceptable specimen:

Specimens fixed in alternative fixatives or metal fixatives (ex. B-plus).  Decalcified specimens.

Reference Range:

ROS1 gene rearrangement present = positive result

ROS1 gene rearrangement not detected = negative result


CPT codes:



Test reported:

Results are reported within 7-10 days