Carcinoma Cell Leukemia (CCL), also called Carcinocythemia, is a rare phenomenon in which non-hematologic tumor cells enter the peripheral blood due to metastasis of tumor cells to the bone marrow. The prognosis is very poor and is often accompanied by thrombosis and intravascular hemolysis (microangiopathic hemolytic anemia (MAHA)).

The circulating tumor cells (breast carcinoma) in this specimen are morphologically reminiscent of abnormal lymphocytes such as can be found in a Burkitt lymphoma. A major drawback is that the relatively large cells are primarily found the edges of the blood smear and thus can theoretically be missed. In this case, the cells were noted by the presence of a population of cells with abnormally high fluorescence in the WDF channel.