CTC clusters in cancer progression and metastasis.

Circulating tumor cells (CTC) in the blood of cancer patients are regarded as potential metastatic seeds, and their detailed characterization holds great promises for more exact prognosis, better diagnosis and therapy of the metastatic cancer. Circulating tumor cell clusters represent different class of CTCs, with specific properties, including high metastatic potential. In this review, we present current opinions on differences between single CTCs and CTC clusters, their mode of dissemination, methods of detection and clinical importance in various types of cancer.