In clinical pathology, the evaluation of white blood cells (WBCs) extends far beyond a simple differential count. While the number of cells is critical, the morphology—the shape, size, and internal structure of the cells—provides vital clues regarding a patient's underlying physiological or pathological state. Much like red blood cells and platelets, leukocyte anomalies must be both identified and quantified to provide a meaningful clinical report.
Quantification of Abnormalities
When reporting morphological findings, pathologists use a standardized scale to communicate the severity of the deviation. This allows clinicians to understand whether a finding is a minor artifact or a significant indicator of systemic disease.
| Severity | Percentage of Total Cells |
|---|---|
| Occasional | |
| Slight (1+) | $5% - 10%$ |
| Moderate (2+) | $10% - 25%$ |
| Marked (3+) | $25% - 50%$ |
| Severe (4+) |
Neutrophil Abnormalities
Neutrophils are often the first responders to inflammation and infection, making their morphology highly sensitive to changes in the body's status.
Nuclear Hyposegmentation: The Pelger-Huët Anomaly
The Pelger-Huët anomaly is a hereditary, non-pathological defect where the nuclei of all granulocytes (neutrophils, eosinophils, and basophils) appear condensed and unsegmented. Because these cells look like immature "bands" but are actually mature cells, they can create a "false left shift" in a blood report. This condition is most common in Australian Shepherds, but can also be seen in Foxhounds, Samoyeds, and Basenjis. Importantly, the function and movement of these neutrophils remain normal.
Nuclear Hypersegmentation
In contrast to hyposegmentation, hypersegmentation occurs when a neutrophil possesses more than five nuclear lobes. This is typically a sign of aging neutrophils that have remained in circulation longer than usual. This can happen in vivo due to endogenous stress (such as cortisol release) or exogenous causes like glucocorticoid administration. It can also occur in vitro if the blood sample is stored in anticoagulant for too long before the smear is prepared.
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