Circulating tumor cells in lung cancer: cluster circulating tumor cells as hybrid epithelial-mesenchymal transition/mesenchymal-epithelial transition (E/M)

Metastasis is the most frequent cause of death among lung cancer patients (1), as such it is crucial to understand the mechanism of cancer metastasis to control the disease. Almost all metastases rise from isolated tumor cells (ITCs) which are dislodged from the original cancer lesion.