Epithelial Cells or Vascular Smooth Muscle Cells in a Peripheral Blood Smear?

To the Editor,

We read the paper submitted to this journal by Lee et al. [1] with great interest. They reported rare epithelial cells in the peripheral blood smear of a 56-year-old male patient. In this blood smear, a few clusters of medium-to-large cells containing elongated oval-grooved nuclei with pale blue frayed cytoplasm at both ends were found at the tail-end of the blood smear. The authors reasoned that these cells were likely epithelial cells, reported as non-hematopoietic cells. The authors then stated that the presence of these abnormal cells could be due to improper mixing before aspiration, to a blunted-tip needle being used, or to repeated unsuccessful venipuncture attempts, and these abnormal cells can also be rarely seen from finger or heel pricks due to transference of skin into the blood tube.

However, confirmation of epithelial cells should be validated by immunohistochemistry, and Lee et al. [1] did not mention the venipuncture status of this patient. As we know, alcohol disinfection is mandatory before venipuncture. Thus, the transference of skin into the blood tube is rare. For this reason, we propose other possible causes of the abnormal cells reported by Lee et al. [1], including vascular smooth muscle cells, subcutaneous fibroblasts, or even the synoviocytes around the elbow joint, from venipuncture of the synovium of the elbow joint. However, whether these cells had the cluster feature is unclear, and other immunohistochemistry methods are needed for corroboration.

Additionally, these abnormal cells reported by Lee et al. [1] also resemble vascular endothelial cells. Vascular endothelial cells have a highly irregular cell morphology, mostly in the shape of long tails or spindles with intact cell membranes and irregular nuclei, often lacking nucleoli. However, vascular endothelial cells could be excluded in this case from our perspective because vascular endothelial cells are often arranged in a single layer and are sparse, regardless of whether they are brought out by vein or bone marrow puncture. Single or several endothelial cells have a certain trend of arrangement, which is inconsistent with the cell cluster feature in the study discussed here.

In conclusion, we appreciate the report offered by Lee et al. [1] for giving us an excellent opportunity to discuss these rare abnormal cells that are seldom seen in hematological examinations.