Fluorescence In Situ Hybridization

Definition

FISH is a molecular cytogenetic technique that detects specific DNA/RNA sequences in cancer cells using fluorescent probes.

Key Applications in Cancer

• Diagnosis:
  • Identifies chromosomal abnormalities (e.g., BCR::ABL1 in CML, HER2 amplification in breast cancer).
  • Confirms fusion genes (e.g., PML::RARA in APL, EWSR1 rearrangements in sarcomas).
• Prognosis & Subtyping:
  • Stratifies risk (e.g., MYCN amplification in neuroblastoma = poor prognosis).
  • Guides therapy (e.g., ALK rearrangements in NSCLC indicate response to ALK inhibitors).
• Monitoring:
• • Tracks minimal residual disease (MRD) (e.g., in CML).

How It Works:

1. Probes bind to target DNA/RNA sequences.
2. Fluorescence microscopy reveals:
   1. Fusions (e.g., overlapping signals).
   2. Amplifications (e.g., extra HER2 copies).
   3. Deletions (e.g., 17p loss in CLL).