An automated diagnostic test approved by the Food and Drug Administration to detect circulating breast cancer cells is unable to detect a particularly aggressive subtype of these cells, researchers report in the Jan. 7 issue of the 

Anieta M. Sieuwerts, PhD, from the Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues examined the ability of the CellSearch circulating tumor cell test-the only diagnostic test currently approved by the FDA to detect and quantify circulating tumor cells-to isolate cells from five subtypes of human breast cancer cells after mixing 50 to 150 cancer cells with 7.5 mL of blood from a healthy donor. The test isolates tumor cells using an antibody to cell surface-expressed epithelial cell adhesion molecule (EpCAM), they note. 

The researchers found that of 19 breast cancer cell lines, those with a luminal or HER2-positive subtype were generally isolated by the assay. However, cells of the normal-like subtype, which are especially aggressive and lack EpCAM expression, were not isolated or were only partially isolated. Normal-like cancer cells express high levels of markers characteristic of basal epithelial and adipose cells and low levels of markers characteristic of luminal epithelial cells, the authors note. 

Sieuwerts AM, Kraan J, Bolt J, et al. Anti-epithelial cell adhesion molecule antibodies and the detection of circulating normal-like breast tumor cells. 

. 2009;101:61-66. Published online at doi:10.1093/jnci/djn419.  

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An automated diagnostic test approved by the FDA to detect breast Ca cells is unable to detect an aggressive subtype of these cells.