What Are Teardrop Cells and Why Do They Form?

Teardrop cells, known in laboratory medicine as dacryocytes, are red blood cells that have been distorted into a shape resembling a teardrop or pear, with one end stretched to a point while the other remains rounded. They show up on a peripheral blood smear and serve as a visual clue that something is disrupting normal red blood cell structure, most often a problem in the bone marrow or the spleen. While they are classically taught as a hallmark of myelofibrosis, the reality of where and why they appear is broader and sometimes surprising.

What a Teardrop Cell Actually Looks Like

Under the microscope, a normal red blood cell is a smooth, biconcave disc. A dacryocyte, by contrast, is an erythrocyte tapered to a point at one end, creating that distinctive teardrop silhouette.¹ The pointed tail can vary in length and sharpness. Some teardrop cells look like elongated pears; others are barely distinguishable from normal cells without careful inspection. Lab technicians typically identify them by scanning a stained blood smear at high magnification.

Teardrop cells belong to the broader category of poikilocytes, a catch-all term for any red blood cell with an abnormal shape. Other poikilocytes include spherocytes (small, round, lacking the usual central pallor), schistocytes (fragmented cells), and target cells (with a bullseye pattern). Each shape points toward a different set of possible causes. The teardrop form specifically signals that something has physically deformed the cell, usually during its passage through tissue.

How Teardrop Cells Get Their Shape

The leading explanation for why red blood cells become teardrop-shaped centers on the spleen and, to a lesser extent, the bone marrow. Both organs contain narrow passageways called sinusoids that red blood cells must squeeze through as part of their normal circulation. A healthy red blood cell is remarkably flexible and can fold itself through tight spaces, then snap back to its disc shape afterward. But when a cell is stiff, swollen, or carrying internal inclusions, forcing through a sinusoid can stretch it beyond the point of elastic recovery. The cell emerges elongated, with one end pulled into a tail.

Red blood cells owe their flexibility to a scaffold of proteins just beneath their outer membrane, sometimes called the membrane skeleton. When this scaffold is intact, the cell can deform and rebound. But when the skeleton is damaged, whether by oxidative stress, abnormal hemoglobin precipitation, or physical strain, the cell loses its ability to bounce back. The resulting permanent deformation produces the teardrop shape. Researchers have described this as damage to the cell membrane occurring during passage through narrow medullary or splenic sinusoids.²

This process is not unique to any single disease. Anything that makes the spleen work harder, makes its sinusoids narrower, or makes red blood cells stiffer can increase teardrop cell production. That is why the same cell shape turns up across conditions as different as myelofibrosis, cancer that has spread to the bone marrow, and certain types of anemia.

The Spleen’s Central Role

Some of the strongest evidence for the spleen’s involvement comes from cases where removing the spleen or shrinking it led to the disappearance of teardrop cells from the blood. In a study of patients with autoimmune hemolytic anemia who had teardrop cells on their smears, splenectomy in one patient and resolution of splenomegaly in another were each followed by the vanishing of these abnormally shaped cells.³ That finding strongly supports the idea that the spleen physically creates the teardrop shape, rather than the cells being released from the bone marrow already deformed.

An enlarged spleen, regardless of the underlying cause, tends to have more congested sinusoids. Red blood cells are forced through tighter corridors under greater pressure. Conditions that cause splenomegaly, from chronic infections to blood cancers, can therefore increase the number of teardrop cells on a smear even when the bone marrow itself is relatively healthy. The spleen also plays a role in a process called extramedullary hematopoiesis, where blood cell production spills over from the marrow into the spleen. When the spleen starts making blood cells on its own, the architecture becomes even more disrupted, and the sinusoidal passages that red blood cells travel through become more tortuous.

When the Bone Marrow Is Crowded Out

The most textbook association with teardrop cells is myelofibrosis, a condition in which the bone marrow gradually fills with scar tissue. As the marrow becomes fibrotic, the normal production of blood cells is impaired. The body compensates by ramping up blood cell production in the spleen and liver, and immature cells that would normally mature in the marrow get released into the bloodstream prematurely. These prematurely released cells, combined with the physical squeezing through an enlarged spleen’s sinusoids, account for the teardrop forms that are so characteristic of this disease.

But myelofibrosis is not the only condition that crowds out normal marrow. Myelophthisis, a form of bone marrow failure caused by replacement of normal tissue with something abnormal, most commonly metastatic cancer, produces a very similar picture. When solid tumors like breast, prostate, or lung cancer spread to the bone marrow, they displace the normal blood-forming cells. The result is extramedullary hematopoiesis in the spleen and the premature release of immature blood cells, including nucleated red blood cells, teardrop forms, giant platelets, and immature white blood cells.⁴ This constellation of findings on a blood smear, when seen together, is called a leukoerythroblastic reaction.

Teardrop Cells in Hemolytic Anemias

Here is where the clinical picture gets more interesting than the textbooks often suggest. Teardrop cells are traditionally associated with bone marrow problems, especially myelofibrosis and marrow infiltration. But research has shown they are also remarkably common in hemolytic anemias, conditions where red blood cells are being destroyed faster than normal.

A study examining blood smears from patients with autoimmune hemolytic anemia (where the immune system attacks the body’s own red cells) and microangiopathic hemolytic anemia (where small blood vessel damage shreds red cells) found dacryocytes on roughly nine out of ten slides in both conditions. Among control slides from patients without hemolytic disease, only about one in five showed any teardrop cells at all. The difference was stark and statistically overwhelming.¹

This finding matters clinically because it means a lab technician or physician who spots teardrop cells on a smear should not automatically jump to myelofibrosis. The mechanism in hemolytic anemias is likely a combination of factors: the spleen is often enlarged because it is working overtime to clear damaged red cells, and the red cells themselves are already structurally compromised before they even reach the splenic sinusoids. A cell whose membrane has been partially chewed up by antibodies or battered against abnormal blood vessel walls is far less able to squeeze through a tight passage and recover its shape.

The Leukoerythroblastic Reaction

Teardrop cells rarely appear alone on a blood smear. When they show up in the context of myelofibrosis or marrow infiltration, they tend to arrive alongside a specific set of companions: nucleated red blood cells (immature red cells that still have a nucleus, which they normally lose before entering the bloodstream), immature white blood cells at various stages of development, and sometimes fragments of megakaryocytes, the giant marrow cells that produce platelets. This combination is the leukoerythroblastic reaction, and it is a distinctive pattern that tells the clinician the bone marrow is under significant stress.

A systematic review on this reaction noted that teardrop cells are present exclusively in myelofibrotic disorders when the full leukoerythroblastic picture is seen, distinguishing those cases from other causes of immature cell release.⁵ In other words, finding immature red and white cells in the blood can happen for several reasons, including severe infection or massive bleeding. But when teardrop cells are part of that picture, the suspicion for marrow fibrosis or infiltration goes up considerably.

The practical upshot for patients: if your doctor orders a peripheral blood smear and the report mentions a leukoerythroblastic picture with teardrop cells, it typically triggers further investigation. That usually means a bone marrow biopsy to look directly at the marrow architecture and determine whether fibrosis, cancer infiltration, or another process is responsible.

Conditions Beyond Myelofibrosis

The list of diseases and situations that can produce teardrop cells is longer than many people expect. Beyond myelofibrosis, marrow infiltration by cancer, and hemolytic anemias, dacryocytes have been reported in:

Thalassemia: Inherited hemoglobin disorders where abnormal hemoglobin chains precipitate inside the red cell, stiffening it and making it vulnerable to deformation during splenic transit.
Megaloblastic anemia: Severe vitamin B12 or folate deficiency can produce large, fragile red cells prone to shape distortion.
Hypersplenism: Any condition causing an overactive, enlarged spleen can produce teardrop cells simply by increasing the mechanical stress on passing red cells.
Kidney disease: Chronic kidney disease alters the biochemical environment red blood cells circulate in, and research in animal models has shown it leads to premature clearance of red cells from the circulation, consistent with membrane damage.⁶

The common thread across all these conditions is that something is either stiffening the red blood cell, damaging its membrane skeleton, enlarging the spleen, or forcing blood cell production into organs not designed for it. Often, more than one of these mechanisms is operating at the same time, which is why teardrop cells can be especially numerous in diseases like myelofibrosis where marrow fibrosis, extramedullary hematopoiesis, and splenomegaly all coexist.

Can Teardrop Cells Disappear With Treatment?

One question patients and clinicians understandably have is whether teardrop cells are permanent or whether they go away when the underlying disease is treated. The answer is encouraging: they are often reversible. A study of fourteen patients with myelofibrosis who received chemotherapy found that the teardrop poikilocytes and other characteristic peripheral blood findings improved with effective treatment.⁷ Similarly, the earlier observation that splenectomy or resolution of splenomegaly eliminated teardrop cells in hemolytic anemia patients confirms the same principle from a different angle.³

This reversibility makes sense given what we know about the mechanism. Individual red blood cells live about 120 days. If the spleen returns to a more normal size, or if marrow fibrosis partially resolves with treatment, newly produced red blood cells will no longer be subjected to the same degree of mechanical stress. The old, deformed cells are gradually cleared and replaced with normal-shaped ones. The speed of improvement depends on how quickly the underlying condition responds and how fast old red blood cells are turned over.

Tracking the number of teardrop cells on serial blood smears can therefore serve as a rough barometer of treatment response. A rising count may signal disease progression, while a falling count suggests the treatment is working. It is not a perfect tool, and clinicians use it alongside other markers like hemoglobin levels, platelet counts, and spleen size, but it is a useful and easily obtained data point.

Why a Few Teardrop Cells on a Smear Might Not Mean Much

It is worth noting that teardrop cells are not always a sign of serious disease. Small numbers of dacryocytes can appear on blood smears from otherwise healthy people, likely as an artifact of slide preparation or the normal variation in red cell shape. The study that found dacryocytes on roughly 89 to 91 percent of hemolytic anemia slides also found them on about 19 percent of control slides.¹ A rare teardrop cell here or there does not carry the same weight as a smear where they are numerous and accompanied by other abnormal findings.

The clinical significance hinges on quantity and context. A few scattered dacryocytes in an otherwise normal-looking smear from a patient with normal blood counts is usually not alarming. But a smear dense with teardrop cells, especially alongside nucleated red blood cells and immature white cells, points strongly toward a marrow or splenic process that warrants further investigation. Lab reports typically note whether poikilocytes are rare, few, moderate, or many, and that grading helps clinicians decide how urgently to investigate.

Slide preparation itself can also introduce false teardrops. Dragging the spreader slide with too much pressure or at the wrong angle can physically stretch cells into pointed shapes that mimic true dacryocytes. Experienced lab technicians learn to distinguish preparation artifacts (which tend to point in the direction of the smear) from true teardrop cells (whose tails can point in any direction). Automated analyzers are getting better at making this distinction too, but the human eye at the microscope still plays an important role.

Machine Learning and the Future of Red Cell Morphology

Reading blood smears is traditionally a manual, labor-intensive skill. A trained technician scans hundreds of cells under the microscope, mentally categorizing each one. It is subjective enough that two technicians can disagree on borderline shapes, and the process takes time that modern high-throughput laboratories do not always have. This has driven growing interest in using machine learning to automate red blood cell classification, including the identification of teardrop cells.

Pilot work using support vector machine models has shown that algorithms can accurately detect and count both normal red blood cells and teardrop cells, though researchers acknowledge that further refinement is needed, particularly with deep learning approaches like convolutional neural networks.⁶ The early results are promising, and if these tools mature, they could help standardize the detection of poikilocytes across laboratories, reduce technician workload, and flag abnormal smears faster.

For now, though, the identification of teardrop cells remains a fundamentally human task in most clinical settings. Automated hematology analyzers can flag samples that look abnormal and suggest a manual smear review, but the final call on whether those oddly shaped cells are true dacryocytes, preparation artifacts, or some other poikilocyte usually falls to a person looking through a microscope. It is one of the areas of laboratory medicine where old-fashioned morphology skills still matter and cannot be fully replaced by technology.

1
PubMed. Dacryocytes are a common morphologic feature of autoimmune and microangiopathic haemolytic anaemia
2
Frontiers in Veterinary Science. Red blood cells morphology and morphometry in adult, senior, and geriatricians dogs by optical and scanning electron microscopy
3
PubMed. Teardrop-shaped red cells in autoimmune hemolytic anemia
4
PubMed. Clinical spectrum of myelophthisis in cancer patients
5
International Journal of Laboratory Hematology. Systematic review about etiologic association to the leukoerythroblastic reaction
6
Research in Veterinary Science. Machine learning-based detection and quantification of red blood cells in Cholistani cattle: A pilot study
7
PubMed. Effect of chemotherapy on tear drop poikilocytes and other peripheral blood findings in myelofibrosis