Circulating Tumor Cells
Circulating tumor cells are neoplastic cells that are passively shed or
actively intravasate into circulation from primary tumors and/or
metastatic deposits. (47). The number of CTCs in cancer patients
correlate with treatment outcome and overall survival (48). The DNA, RNA
and protein content of CTCs can be evaluated for molecular
characterization informative of native tumor tissue (49). CTCs
constitute a small fraction of cells in circulation-1 in
109 cells (50) and thus various techniques using
distinct biological and physical properties of CTCs are used to
differentiate and isolate them from leucocytes, erythrocytes and other
cells in a blood sample. The predominant method of CTC isolation
involves enrichment for cells with EPCAM expression and lack of CD45
expression (51,52,53). This is not applicable to circulating DLBCL cells
and cells from other hematological malignancies which express CD45 and
lack EpCAM expression. In addition, the low abundance of CTCs makes
their use in early stage of disease challenging. Other challenges with
use of CTC as liquid biopsy is the need for prompt processing of whole
blood after collection in most isolation platforms (54) precluding the
potential for biobanking specimens for future analyses or use of
archival biobanked specimens for studies.