FISH for RET Gene Rearrangements

RET (10q11) 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.  RET (10q11) gene fusions can be found in 1-2% of NSCLC, more commonly in adenocarcinomas of never or light smokers, whose tumors lack EGFR and KRAS mutations.  Patients with RET gene rearrangements, characteristically due to KIF5BRETCCDC6RETNCOA4RET, and TRIM33RET fusion, rendering the tumors sensitive to RET inhibitors such as cabozantinib (while resistant to EGFR tyrosine kinase inhibitor therapies). 

https://www.nccn.org/professionals/physician_gls/pdf/nscl.pdf

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). 

Methodology:
Fluorescent in-situ hybridization (FISH)

Forms:
Molecular pathology requisition form

Transport:
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:
RET gene rearrangement present = positive result
RET gene rearrangement not detected = negative result

CPT codes:
88377

Test reported:
Results are reported within 7-10 days