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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Bone Marrow Cell Identification<br />
division into three subtypes (from the original FAB<br />
classification): L1, L2, <strong>and</strong> L3. The subtypes are<br />
useful only in morphologic recognition <strong>and</strong> are not part<br />
<strong>of</strong> current leukemia classification. On one end <strong>of</strong> the<br />
spectrum, L1 lymphoblasts are small cells with scant<br />
cytoplasm, round nuclei, <strong>and</strong> homogeneous chromatin<br />
that is coarser <strong>and</strong> more compact than other blasts.<br />
Nucleoli are inconspicuous due to the dense<br />
chromatin. L2 lymphoblasts are intermediate-sized<br />
cells with a scant to moderate amount <strong>of</strong> cytoplasm<br />
<strong>and</strong> round, oval, or irregular nuclei that may be<br />
indented, folded, or clefted. One or more large nucleoli<br />
may be seen. These cells <strong>of</strong>ten resemble myeloblasts<br />
or monoblasts. At the other end <strong>of</strong> the spectrum, what<br />
was previously classified as L3 lymphoblasts are uniformly<br />
large, round cells with round to oval nuclei with coarse<br />
chromatin <strong>and</strong> one or more prominent nucleoli. These<br />
should now be classified as Burkitt cells or circulating<br />
Burkitt lymphoma. These cells characteristically have a<br />
moderate amount <strong>of</strong> deeply basophilic cytoplasm<br />
containing frequent, similar sized, round vacuoles.<br />
Auer rods are absent in all lymphoblasts.<br />
Because lymphoblasts are quite variable in<br />
appearance, it is <strong>of</strong>ten impossible to correctly classify<br />
an individual cell based on the morphology alone.<br />
Lymphoblasts can be morphologically indistinguishable<br />
from other types <strong>of</strong> blasts <strong>and</strong> lymphoma cells. For<br />
identification purposes, one should classify individual<br />
cells exhibiting this type <strong>of</strong> morphology as blast cells<br />
when additional confirmatory information is unavailable.<br />
Gaucher Cell, Pseudo-Gaucher Cell<br />
A Gaucher cell is a form <strong>of</strong> histiocyte (macrophage)<br />
that is ovoid <strong>and</strong> measures 20 to 90 μm in diameter<br />
with a low nuclear-to-cytoplasmic ratio (less than 1:3).<br />
It contains a small, round or oval nucleus with indistinct<br />
nucleoli. The chromatin is coarse. The cytoplasm is<br />
abundant, lipid-laden (containing glucosylcerebroside),<br />
<strong>and</strong> stains gray to pale blue. Fibrillar, reticular, “crumpled<br />
cellophane,” or “wrinkled tissue paper” appearance<br />
<strong>of</strong> the cytoplasm is characteristic. This distinctive linear<br />
striation results from lamellar bodies stacked within<br />
secondary phagolysosomes.<br />
A morphologic variant shows less striking linear striation<br />
<strong>and</strong> contains a small number <strong>of</strong> fine blue cytoplasmic<br />
granules. The cells stain for PAS <strong>and</strong> lysosomal enzymes<br />
such as acid phosphatase (tartrate-resistant) <strong>and</strong><br />
nonspecific esterase. Gaucher disease is an inherited<br />
deficiency <strong>of</strong> beta-glucocerebrosidase, leading to<br />
accumulation <strong>of</strong> glucosylcerebroside in a variety <strong>of</strong><br />
tissues, including bone, liver, lung, <strong>and</strong> brain.<br />
Pseudo-Gaucher cells are indistinguishable from true<br />
Gaucher cells on light microscopy, although they differ<br />
ultrastructurally.<br />
They are phagocytic cells engaged in catabolism <strong>of</strong><br />
glycoside from the membranes <strong>of</strong> dead cells. These<br />
macrophages have normal amounts <strong>of</strong> beta-<br />
glucocerebrosidase enzyme <strong>and</strong> are postulated to<br />
arise from excessive cell breakdown with an overload<br />
<strong>of</strong> glucoceramide.<br />
Histiocyte, Sea Blue<br />
These bone marrow cells are macrophages (histiocytes)<br />
that have abundant cytoplasm filled with variably sized<br />
bluish or bluish green globules or granules <strong>of</strong> insoluble<br />
lipid pigment called ceroid. Ceroid, Latin for wax-like,<br />
is a pigment <strong>of</strong> uncertain identity thought to represent<br />
partially digested globosides derived from cell<br />
membranes. In H&E-stained marrow sections, the<br />
histiocytes appear foamy or slightly eosinophilic <strong>and</strong><br />
contain a variable number <strong>of</strong> yellow to yellow-brown<br />
granules. They are distinguished from hemosiderin-laden<br />
macrophages (siderophages) by a negative Prussian<br />
blue stain. Small numbers <strong>of</strong> sea-blue histiocytes may be<br />
seen in normal marrow <strong>and</strong> should not be considered<br />
a pathologic finding. Large numbers occur in marrow,<br />
spleen, <strong>and</strong> liver in an inherited disorder <strong>of</strong> unknown<br />
cause called the “sea blue histiocyte syndrome.”<br />
Occasional to moderate numbers <strong>of</strong> sea-blue<br />
histiocytes can be seen in other lipid storage diseases,<br />
hyperlipidemias, chronic myelogenous leukemia,<br />
patients on hyperalimentation, <strong>and</strong> in any disorder<br />
with massively increased intramedullary cell destruction.<br />
Lipocyte (Adipocyte, Fat Cell)<br />
The lipocyte, a normal constituent <strong>of</strong> yellow or fatty<br />
bone marrow, is a large (25 to 75 μm in diameter) cell<br />
with a very small, densely staining, eccentric nucleus.<br />
The fat-laden cytoplasm is abundant <strong>and</strong> <strong>of</strong>ten consists<br />
<strong>of</strong> a single, colorless fat vacuole, giving the cell a<br />
signet-ring appearance. Alternately, it may appear<br />
to contain numerous large fat vacuoles, separated<br />
by delicate, light blue or pink cytoplasm. Eosinophilic<br />
fibrils may be present, both within the cytoplasm <strong>and</strong><br />
extending outward from the cell margins. The lipocyte,<br />
a fat-producing cell, should be distinguished from a<br />
macrophage with phagocytized fat (or lipophage). The<br />
lipid-laden macrophage contains small, uniform lipid<br />
particles, giving the cytoplasm a foamy or bubbly<br />
appearance.<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>