Micrometastases were originally defined by pathologists as small occult metastases (<0.2 cm in greatest dimension). With the recent development of more sensitive diagnostic tools, such as immunocytochemistry and polymerase chain reaction (PCR), the term has been used more liberally in the literature. It now includes isolated disseminated tumor cells (DTC) present in the peripheral blood or in a secondary organ (in particular bone marrow) or in a lymph node, classified as “tumor-free” by conventional histopathological analysis. Considering the different biology of true micrometastases and isolated DTC, both types of findings should be distinguished.
During the past decade, sensitive techniques have been developed that allow now the detection of DTC in the blood and bone marrow (BM) at the single cell level. DTC must be separated from billions of erythrocytes and millions of leucocytes present in the blood and bone marrow sample. For this...