ABSTRACT
The spread of cancer requires the presence of circulating tumor cells (CTCs), which are rare cells surrounded by billions of normal hematopoietic cells in the bloodstream. It is believed thatCTCs tend to metastasize to certain organs, thus, their presence may determine invasive tumor behavior. Generally, these cells are undetectable by conventional histopathological analysisand imaging exams with high resolution. Therefore, more sensitive immunohistochemical and molecular assays have been developed that have allowed the specific detection of metastatic tumor cells in regional lymph nodes, peripheral blood and bone marrow. This article reviews theliterature regarding CTCs and tumors of the breast, colorectal, pancreas and lung as it pertains to forms of detection and clinicopathological correlations, in addition to future outlooks