From the Guidelines
Smudge cells are characteristic morphologic features found in chronic lymphocytic leukemia (CLL), representing damaged or fragile lymphocytes that appear as cell debris, also known as Gumprecht nuclear shadows, on a blood smear examination. These cells are typically small, mature lymphocytes with a narrow border of cytoplasm and a dense nucleus lacking discernible nucleoli, which may rupture during the preparation of the blood smear due to their inherent fragility 1. The presence of smudge cells is a diagnostic feature of CLL, and they can be found admixed with other characteristic cells, such as larger or atypical cells, cleaved cells, or prolymphocytes.
- Key characteristics of smudge cells include: + Appearance as amorphous bluish stains with no clear cellular structure + Resembling smudged nuclear material without an intact cell membrane + Resulting from reduced expression of vimentin and other cytoskeletal proteins + Comprising up to a significant percentage of lymphocytes in CLL samples
- The presence and percentage of smudge cells can sometimes correlate with disease progression in CLL, making them a useful diagnostic indicator 1. While primarily associated with CLL, smudge cells can occasionally be seen in other lymphoproliferative disorders or in samples that have undergone mechanical trauma during processing.
From the Research
Definition of Smudge Cells
- Smudge cells are defined as ruptured or destroyed cells, most commonly lymphocytes, where cytoplasm and nuclei get smudged during the smear test of a patient's blood or preparation of slides 2.
- They are also referred to as Gumprecht shadows and are characteristic of chronic lymphocytic leukemia (CLL) cells that are ruptured during smear preparation 3, 4.
Clinical Significance of Smudge Cells
- The presence of smudge cells on a blood smear can be used as a prognostic test in CLL, with a higher percentage of smudge cells indicating a better prognosis 3, 5, 4.
- Studies have shown that patients with a higher percentage of smudge cells have a longer progression-free period and overall survival compared to those with a lower percentage of smudge cells 5, 4.
- The percentage of smudge cells has also been shown to correlate with other prognostic markers, such as vimentin expression and immunoglobulin heavy chain gene mutation status 3, 4.
Laboratory Practice and Smudge Cells
- Smudge cells are commonly observed on the blood smears of patients with CLL, and excluding them from the manual differential count can yield unreliable results 6.
- Counting smudge cells as lymphocytes on nonalbuminized blood smears can provide reliable manual differential count results 6.
- Automated differential counts can also be used as a substitute for manual differential counts, and reportable results can be generated by the analyzer on a significant percentage of specimens 6.
Management and Referral
- If a persistent or higher number of smudge cells are found during a 3-month period, it is recommended to refer the patient to a hematologist for further evaluation and management 2.
- Regular control of lab work is also recommended when smudge cells are found to ensure accurate diagnosis and treatment 2.