ROS Proto-Oncogene 1 (ROS1)

NOTE: Our laboratory offers multiple testing options for non-small cell lung cancer. Please see our Lung Cancer overview page.


ROS1 rearrangements have been reported in approximately 0.5-2% of non-small cell lung carcinomas (NSCLC) and are mutually exclusive with driver mutations in the EGFR, KRAS, or ALK genes.  Rearrangements can occur with a number of different partner genes, however all rearrangements involve the 3’ region of the ROS1 kinase domain with the 5’ region of the partner gene. Unbalanced rearrangements can also occur and result in the loss of the non-oncogenic reciprocal fusion gene.

The resulting fusion generates a constitutively active tyrosine kinase. Constitutively active ROS1 fusions are oncogenic and NSCLC carrying these rearrangements are sensitive to ROS1 tyrosine kinase inhibitor therapies. 


Stage IIIB/IV non-small cell, non-neuroendocrine lung adenocarcinoma with equivocal ROS1 IHC.


ROS1 FISH is typically performed as a confirmatory test for equivocal or positive ROS1 IHC results. FISH testing is not required for negative ROS1 IHC results.

  1. Completed CGL Solid Tumour Testing requisition form
    1. ROS1 screening by IHC is automatically performed in combination with EGFR testing, when either of the following tests are ordered:
      1. Select Oncopanel OR
      2. Select “Pretreatment: EGFR (hotspots)
  2. FFPE Tumour specimen (see Specimen Guidelines)
    • A minimum of 10% tumour content and at least 200 nuclei is required


Fourteen calendar days from receipt of specimen and completed, signed requisition form.


Specimens are reported as Positive for a rearrangement, Negative for a rearrangement, or Negative for a rearrangement – extra signals.


FISH analysis is performed on the provided paraffin embedded tissue using the ROS1 (6q22) dual-colour, break-apart probe (BioCare Medical).