A method for detecting the presence or absence of individual circulating cancer cells in a centrifuged sample of anticoagulated whole blood contained in a container which container also contains an insert that forms a well-defined free volume in the container, said blood sample having been combined with one or more epitope-specific labeling agents that are operative to produce a characteristic signal result on individual cancer cells, and which result is defined by the presence of one or more epitopes on the individual cancer cells, and said blood sample having also been combined with a colorant which is operable to clarify cell morphology in all nucleated cells in the blood sample, said method comprising the steps of identifying by cell morphology all nucleated cells disposed in said well-defined annular free volume, and further characterizing all identified individual nucleated cells as cancer cells or non-cancer cells epitopically, said identifying and characterizing steps being performed in situ in the container.