Smudge cells (SCs) also known as “basket cells”, are remnants of B lymphocytes ruptured during slide preparation (photo below). Although at low numbers (~0-5% of lymphocytes) SCs may be observed in healthy individuals, when found at higher numbers (>10%) they are associated with chronic lymphocytic leukemia (CLL) and other lymphoproliferative diseases1; the percentage of SCs may not discriminate between these malignancies, however2.
For nearly a century, SCs were thought to be just an artifact of slide preparation resulting from the fragility of CLL cells3. Although the mechanism accounting for the appearance of SCs is still unclear, their formation is inversely correlated with B cell content of vimentin, a cytoskeletal protein essential for rigidity and integrity of lymphocytes 3-5.
High vimentin expression is associated with an aggressive variant of CLL and shorter survival times3-5. Therefore, higher number of SCs at the time of CLL diagnosis (>20% or >30%) may actually indicate a better prognosis4-6!
Photo courtesy of U.S. National Library of Medicine
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- Petrakis NL, Lieberman E, Fullerton J. The dead leukocyte content of the blood in normal and leukemic patients. Blood. 1957 Apr;12:367-72. https://www.ncbi.nlm.nih.gov/pubmed/13412765
- Matos DM, Perini G, Kruzich C, Rego EM, Falcao RP. Smudge cells in peripheral blood smears did not differentiate chronic lymphocytic leukemia from other B-cell chronic lymphoprolipherative diseases. Rev Bras Hematol Hemoter. 2009;31:333–6. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-84842009000500010
- Nowakowski GS1, Hoyer JD, Shanafelt TD, et al. Percentage of smudge cells on routine blood smear predicts survival in chronic lymphocytic leukemia. J Clin Oncol. 2009;27:1844-9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2668708/
- Nowakowski GS, Hoyer JD, Shanafelt TD, et al. Using smudge cells on routine blood smears to predict clinical outcome in chronic lymphocytic leukemia: a universally available prognostic test. Mayo Clin Proc. 2007;82:449-53. https://www.mayoclinicproceedings.org/article/S0025-6196(11)61073-2/fulltext
- Johansson P, Eisele L, Klein-Hitpass L, et al. Percentage of smudge cells determined on routine blood smears is a novel prognostic factor in chronic lymphocytic leukemia. Leuk Res. 2010;34:892-8. https://reference.medscape.com/medline/abstract/20353875
- Gogia A, Raina V, Gupta R, et al. Prognostic and predictive significance of smudge cell percentage on routine blood smear in chronic lymphocytic leukemia. Clin Lymphoma Myeloma Leuk. 2014;14(6):514-7. https://www.clinical-lymphoma-myeloma-leukemia.com/article/S2152-2650(14)00049-4/abstract
Contributed by Khin-Kyemon Aung, medical student, Harvard Medical School, Boston.