Bi-directional sequencing of exon 4 of the KRAS gene corresponding to amino acids R97 through Q150. Codon 117 and 146 mutations are detected. For solid tumors, tumor enrichment is performed before extraction. This test may be ordered separately or by reflex after standard KRAS Mutation Analysis. Testing is available separately or in combination with BRAF, HRAS and NRAS in the RAS/RAF Panel. Testing is approved for specimens from the state of New York.
This assay complements the standard KRAS Mutation Analysis of exons 2 and 3. Mutations in exon 4 are detected in approximately 1-4% of colorectal cancers. Exon 4 analysis is appropriate for detecting activating mutations that may confer resistance to EGFR-targeted inhibitors and predicts sensitivity to MEK inhibition.
- FFPE solid tumor tissue: Paraffin block is preferred. Alternatively, send 1 H&E slide plus 5-10 unstained slides cut at 5 or more microns. Please use positively-charged slides and 10% NBF fixative. Do not use zinc fixatives.
- Fine needle aspirate (FNA): Requisition must note specimen is FNA. Fresh cells in suspension, unstained air-dried smears (approx. 6-8 slides), or FFPE cells blocks are acceptable if pathologist attaches note verifying sample has >30% tumor or abnormal cells (required). Minimum 10^6 cells.
Use cold pack for transporting block during summer to prevent block from melting. Slides can be packed at room temperature.