Acute Leukemias - Republican Scientific Medical Library

112 Chapter 7 · Acute Lymphoblastic Leukemia: Clinical Presentation, Diagnosis, and Classification
Fig. 7.1. Varied cytomorphology of lymphoblasts in comparison to
Burkitt leukemia cells and hematogones (Wright-stained blood and
bone marrow aspirate smears). (a) Small uniform blasts, previously
called “L1” type, are about two times the size of erythrocytes, and
have a smudgy homogenous chromatin without prominent nucleoli.
Comparison to small lymphocyte (right) is always helpful. (b) Varied
lymphoblasts, including numerous larger blasts with more open
chromatin, prominent nucleoli and abundant cytoplasm (previously
considered “L-2 “ type). The presence of a few small “L1” blasts in the
background is always helpful in considering ALL. (c) Burkitt leukemia
cells (previously called “L3” blasts) are usually distinctive with
homogeneous large size, and deep blue cytoplasm with prominent
“L1” and “L2” blasts, recognized in Wright-stained material,
is also usually not possible. Burkitt leukemia
does, however, have a particular histologic pattern.
The features are similar to the lymph node involvement
by Burkitt lymphoma. These features are illustrated in
Fig. 7.2.
Hypocellular presentations of ALL are relatively
rare, but can present a diagnostic challenge due to the
paucity of cells and limited material for immunophenotyping
[20]. Some cases of ALL can present with frank
fibrosis [21], but increased reticulin is more common.
Some cases are inaspirable due to the fibrosis or to
the dense packing of the marrow by lymphoblasts. Necrosis
is present in a small number of cases and can
complicate the diagnosis, due to the lack of viable cells
for either morphologic evaluation or for immunophe-
vacuoles. Vacuoles can, however, be seen in some cases of AML and
ALL. (d) Some lymphoblasts can be small with more clumped
chromatin, and can be difficult to distinguish morphologically from
CLL cells. (e) Granular lymphoblast (arrow). These blasts may resemble
myeloblasts, but the granules are myeloperoxidase negative.
(f) Lymphoblast with nuclear cleft, (g) So-called “hand-mirror” cells
are sometimes an artifact of poor preparations, as they are not
equally distributed on the slide. (h) Hematogones (arrows) resemble
lymphoblasts. They can be distinguished by flow immunophenotyping,
and due to the associated background of small lymphocytes
and regenerating bone marrow.
notyping [22]. Necrosis can be focal or widespread,
and can recur with relapsed disease. Occasional cases
can show bone changes, which include osteoporosis or
osteopenia [23].
In some cases of ALL the principle manifestation of
disease is extramedullary [24]. This is not uncommon
in precursor-T-cell ALL/lymphoma which can present
with a mediastinal mass and lymphadenopathy. Other
sites that may be identified prior to blood and bone
marrow disease include lymph node, skin, testes, and
CNS. Whenever there is concern of a lymphoblastic process
in an extramedullary location, careful review of the
blood and evaluation of the marrow is imperative.
Differential diagnostic considerations based on the
cytomorphologic and histologic features of blasts in
the peripheral blood and marrow depend in part on