This instability is usually due to the propensity of these regions to misalign during DNA repair, exacerbated by defects of the appearance of replication proteins (like FEN1 or Pol δ) that ubiquitously affect the integrity of the genome.
Linkage analysis and chromosomal rearrangement revealed the cause of SCS to be mutations in the TWIST gene (twist transcription factor gene) located on chromosome 7p21.
About 4% of patients with non-small cell lung carcinoma have a chromosomal rearrangement that generates a fusion gene between EML4 ('echinoderm microtubule-associated protein-like 4') and ALK ('anaplastic lymphoma kinase'), which results in constitutive kinase activity that contributes to carcinogenesis and seems to drive the malignant phenotype.