Hematology and Clinical Microscopy Glossary - College of American ...
Hematology and Clinical Microscopy Glossary - College of American ...
Hematology and Clinical Microscopy Glossary - College of American ...
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8<br />
Blood Cell Identification<br />
primarily on the stage <strong>of</strong> cytoplasmic maturation.<br />
Megaloblastic cells are larger in size than their<br />
normoblastic counterparts. Megaloblastic changes<br />
may also be found in other hematopoietic cell series.<br />
Nucleated Red Cell, Dysplastic<br />
Dyserythropoiesis or abnormal red cell differentiation<br />
encompasses both megaloblastic maturation <strong>and</strong><br />
dysplastic maturation. Megaloblastic maturation<br />
is characterized by varying degrees <strong>of</strong> nuclear-<br />
cytoplasmic maturation dyssynchrony. Vitamin B12<br />
<strong>and</strong> folate deficiencies are the classic examples <strong>of</strong><br />
megaloblastic maturation, but stem cell abnormalities<br />
associated with myelodysplasia, toxins, drugs, or any<br />
number <strong>of</strong> other extrinsic factors may also alter<br />
DNA production, resulting in lesser degrees <strong>of</strong><br />
maturation dyssynchrony or megaloblastoid change.<br />
True megaloblastic red cells exhibit dramatic maturation<br />
differences between the nucleus <strong>and</strong> cytoplasm. This<br />
dyssynchrony is not as obvious in megaloblastoid red<br />
cells. The chromatin is more clumped <strong>and</strong> the<br />
chromatin str<strong>and</strong>s are much coarser than in a<br />
corresponding megaloblastic nucleated red cell. The<br />
clear spaces between the dense chromatin str<strong>and</strong>s are<br />
more prominent in megaloblastoid red cell nuclei. The<br />
changes are most noticeable in the later stages <strong>of</strong> red<br />
cell maturation as hemoglobin production in the<br />
cytoplasm is more demonstrable. Pronormoblasts are<br />
too young to display overt nuclear-cytoplasmic<br />
dyssynchrony. Dysplastic nucleated red blood cells will<br />
exhibit strikingly abnormal nuclear features. The nucleus<br />
may be enlarged, grotesquely shaped, lobated,<br />
fragmented, or multinucleated. The cytoplasm may<br />
be vacuolated <strong>and</strong> contain multiple Howell-Jolly<br />
bodies or exhibit coarse basophilic stippling. If the<br />
red cell is severely dysplastic, a PAS stain may show<br />
clumped cytoplasmic positivity. Megaloblastoid <strong>and</strong><br />
dysplastic nucleated red cells are found in many<br />
different conditions, such as acute myeloid leukemias<br />
(including erythroleukemia), myelodysplasia, chronic<br />
myeloproliferative disorders, <strong>and</strong> congenital<br />
dyserythropoietic anemias. Megaloblastoid change <strong>and</strong><br />
lesser degrees <strong>of</strong> dysplasia may also develop in states<br />
<strong>of</strong> erythroid hyper-proliferation, as well as following<br />
exposure to certain toxins, heavy metals, antibiotics,<br />
antimetabolites <strong>and</strong> excess alcohol.<br />
Acanthocyte (Spur Cell)<br />
Acanthocytes are densely stained spheroidal (lacking<br />
central pallor) red cells with multiple (usually three to<br />
20), irregularly distributed, thorn-like spicules <strong>of</strong> variable<br />
size, <strong>of</strong>ten with drumstick ends. Acanthocytes are<br />
classically described in association with hereditary<br />
abetalipoproteinemia (hereditary acanthocytosis).<br />
In addition, these cells are <strong>of</strong>ten seen in significant<br />
numbers in severe (end-stage) liver disease,<br />
hepatorenal failure, anorexia nervosa, <strong>and</strong> chronic<br />
starvation. (In the latter two disorders, they appear as<br />
irregularly shaped erythrocytes with multiple blunt<br />
projections.) A small number <strong>of</strong> acanthocytes may<br />
be seen in other forms <strong>of</strong> severe hemolytic anemia,<br />
particularly after splenectomy. Acanthocytes are<br />
rarelyencountered in otherwise normal blood smears<br />
(one or two per smear). In such smears, they represent<br />
older, senescent red cells approaching their extremes <strong>of</strong><br />
life (120 days). It is logical, therefore, that acanthocytes<br />
should readily be found in blood smears in the postsplenectomy<br />
state because <strong>of</strong> diminished splenic activity in<br />
removal <strong>of</strong> such poikilocytes.<br />
Bite Cell<br />
Bite cells are red cells from which precipitated,<br />
denatured masses <strong>of</strong> hemoglobin (Heinz bodies) have<br />
been pitted by the spleen. Precipitation is a function<br />
<strong>of</strong> oxidant injury to hemoglobin by certain drugs or<br />
denaturation <strong>of</strong> unstable hemoglobin variants. In<br />
particular, patients with glucose-6-phosphate<br />
dehydrogenase (G-6-PD) deficiency may be<br />
predisposed to such oxidant injury. The net result <strong>of</strong> the<br />
act <strong>of</strong> pitting is a variety <strong>of</strong> peripheral red cell defects,<br />
ranging from tiny arc-like nibbles to large bites.<br />
“Bitten” red cells may show multiple peripheral defects.<br />
Symmetrical equatorial defects result in the formation <strong>of</strong><br />
“apple-core” poikilocytes. Giant single bites may result<br />
in the formation <strong>of</strong> poikilocytes morphologically<br />
indistinguishable from the “helmet” cells <strong>of</strong><br />
fragmentation anemias. As in the fragmentation<br />
anemias, spherocytes are almost invariably present,<br />
albeit in small numbers.<br />
Blister Cell/Prekeratocytes<br />
Blister cells are erythrocytes in which the hemoglobin<br />
appears to be concentrated on one side <strong>of</strong> the cell,<br />
leaving just a thin membrane on the other side. This<br />
produces the appearance <strong>of</strong> large vacuoles with fuzzy<br />
margins. Blister cells are most characteristically seen in<br />
sickle cell disease, in which they are considered a sickle<br />
cell variant. Similar cells, eccentrocytes, may be seen<br />
in the setting <strong>of</strong> oxidant hemolysis. Blister cells may be<br />
similar to prekeratocytes.<br />
Prekeratocytes are red cells containing one or two<br />
sharply defined, usually submembranous vacuoles. By<br />
electron microscopy, these vacuoles are actually<br />
“pseudovacuoles” representing fusion <strong>of</strong> opposing<br />
red-cell membranes with exclusion <strong>of</strong> intervening<br />
<strong>College</strong> <strong>of</strong> <strong>American</strong> Pathologists 2012 <strong>Hematology</strong>, <strong>Clinical</strong> <strong>Microscopy</strong>, <strong>and</strong> Body Fluids <strong>Glossary</strong>