Activating mutations in the NRAS gene occur in approximately 2-3% of colorectal carcinomas, 20% of melanomas, and a variety of other human cancers. NRAS mutations are predominantly single nucleotide substitutions, occurring most frequently within exons 2 and 3 at codons 12, 13, and 61. These NRAS mutations are associated with poor clinical response to epidermal growth factor receptor (EGFR) targeted therapies in patients with colorectal cancer. This DNA test is performed by targeted next-generation sequencing to detect mutations within sequenced regions of NRAS exons 2, 3, and 4 (NM_002524.4; Hg19 chr1:115285690-115258774, chr1:115256505-115256584, chr1:115252191-115252305) including codons 12, 13, and 61. Specimens should contain an adequate proportion of neoplastic cells (>20%) in the area to be extracted to ensure mutation detection.
Interpretive report provided.
This test does not detect copy number variants or translocations and may not detect large insertions, deletions or duplications. This test may also fail to detect mutations below the limit of detection of this assay (approximately 5%). Rare polymorphisms may lead to false negative results. Discordant results are rarely observed between metastatic and primary specimens. The clinical implications of the findings as indicated in the test report may change based on evolution of the scientific literature.
This test is for the purpose of detecting somatic mutations in neoplastic tissue. While this test cannot definitively distinguish between somatic and germline variants, know germline variants within the targeted regions will not be reported. Alternative testing is required if there is concern for a clinically relevant germline alteration.
- N-RAS Mutation Detection
For formalin-fixed, paraffin-embedded tissue, a block containing an area with a high percentage of neoplastic cells (for micro-/macro-dissection) is preferred. Unstained, UNBAKED slides (5-8, 10-micron slides; 10-15 if few neoplastic cells are present) with associated H&E stained slide are also acceptable. Decalcified tissue or other fixatives will be accepted and the assay attempted, however these may result in failed testing due to degraded nucleic acid. Both blocks and slides should be stored at room temperature. A Diff-Quik or Papanicolaou stained aspirate smear (preferable containing a high percentage and overall amount of neoplastic cells) is also acceptable. Store at room temperature..
Previously extracted DNA may be accepted; however, the extracting laboratory must take responsibility for ensuring that viable, neoplastic cells comprise at least 20% of cellularity within the extracted sample.
By ordering this test the clinician acknowledges that informed consent has been obtained from the patient as required by applicable state or federal laws and the ordering clinician has authorization from the patient permitting MLabs to report the test results to the ordering clinician. Test may include microdissection billed as a separate additional charge. Test includes pathologist interpretation of results billed as a separate additional charge. This test is not available without interpretation.