Fish-shaped erythrocytes and pincer cells co-occur in distinct hematological disorders and are associated with anemia severity.

OBJECTIVES

Red blood cell (RBC) morphology in peripheral blood smears (PBS) remains essential for the differential diagnosis of anemia and other hematologic disorders. As yet unclassified poikilocytes, fish-shaped RBCs and pincer (mushroom-shaped) cells are rarely observed but have been described as "bizarre erythrocytes" and linked to hereditary spherocytosis. This study aimed to investigate their relevance across a spectrum of hematologic diseases and provide a basis for future morphological standardization.

METHODS

Peripheral blood smears from 251 specimens were systematically reviewed, including cases of iron deficiency anemia (IDA), β-thalassemia minor (BTM), sickle cell disease (SCD), microangiopathic hemolytic anemia (MAHA), autoimmune hemolytic anemia (AIHA), hereditary spherocytosis (HS), hereditary elliptocytosis (HE), vitamin B12/folate deficiency, myelodysplastic neoplasms (MDS), primary myelofibrosis (PMF), malaria, liver disease (LD), and healthy controls. Abnormal RBC morphologies were quantified as cells per 20 high-power fields at 1,000 × magnification. Group comparisons used the Mann-Whitney U test and correlations were assessed by Spearman's rank correlation.

RESULTS

Numbers of fish-shaped and pincer cells were significantly increased in IDA, BTM, MDS, HE, PMF, and vitamin B12/folate deficiency with a strong positive intercorrelation (p<0.01) in most of these diseases. Pincer cells were also elevated in HS and hemoglobin levels were negatively correlated with both fish and pincer cells across all disorders studied (p<0.0001).

CONCLUSIONS

Fish-shaped RBCs and pincer cells represent abnormal erythrocyte morphologies associated with a range of hematologic disorders and correlate with severity of anemia. Their strong intercorrelation suggests a shared pathophysiologic mechanism or may reflect different stages of a common morphological process.