What Defines a CTC?

The FDA-cleared CELLSEARCH® Circulating Tumor Cell Test defines the CTC phenotype as outlined below. The Research Use Only (RUO) tests have a broader definition. Learn more

  • EpCAM+
  • Cytokeratins 8+, 18+, and/or 19+
  • DAPI+
  • CD45-
  • Intact cell > 4 microns
  • Fragments are captured but not counted

Detecting rare cells enables research innovation and helps expedite the drug discovery and development process.

Frequency of CTCs1


  1. Allard WJ, Matera J, Miller MC, et al. Tumor cells circulate in the peripheral blood of all major carcinomas but not healthy subjects or patients with nonmalignant diseases. Clin Cancer Res 2004;10:6897-6904.