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Title: Case Study: Feline spinal cord gemistocytic
astrocytoma
Authors: Elisângela Olegário da Silva; Raquel Beneton Ferioli; Kleber Moreno; Ana Paula F.R.L.
ID: 29645-2011
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with
some minor grammar faults see text
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4.REPORT: This case report will aid in the diagnosis
of this rare condition in the cat. The report is generally well written and histopathological findings support the diagnosis. There is
extensive information concerning the condition in other species in the
Introduction and the Discussion which may be superfluous in this case. It would
be useful to provide maybe a similar differential with image. In text change
“In feline” to In felines. Accept with minor changes
see attached revised manuscript below.
ABSTRACT
Primary spinal cord tumors are rare
in cats. A six-year-old, intact male Siamese cat had a history of progressive hemiparesia, muscle atrophy in the right thoracic limb and
pain in that region. Neurological examination revealed increased reflexes,
hyperesthesia and propioceptive deficit in the right
thoracic limb. Medical therapy was initiated, but neurological signs were
progressive and severe, affecting the pelvic limbs. The owner opted for
euthanasia. Gross exam showed a swollen area in the C6 region of the spinal
cord. Histopathological examination showed diffuse
proliferation of large cells with abundant eosinophilic
cytoplasm and eccentrically located large nuclei with prominent 8positive
staining for S100, vimentin and GFAP (glial fibrillar acid protein) and
negative staining for macrophage antigens (lysozyme
and LN-5). Based on histopathological and immunohistochemical features, the diagnosis of gemistocytic astrocytoma was
made.
INTRODUCTION
Neoplasias
of the central nervous system (CNS) can be neuroectodermal,
mesodermal or of nervous root origin (Jones, 2006). Gliomas are the most common type of tumor of neuroectodermal origin in humans (Rasheed
and Bigner, 1997, Gavin et al., 2002) and animals (Koestner and Higgins, 2002). Astrocytomas
comprise the majority of canine gliomas but are
uncommon in feline (Summers et al., 1995). Astrocytomas
occur most commonly in the pyriform lobe, convexity
of the cerebral hemisphere, thalamus and hypothalamus, and in the midbrain, but
they are rarely found in the cerebellum and spinal cord (Storts,
1995; Koestner and Higgins, 2002).
In felines, primary tumors of the
CNS are uncommon (Fondevila et al., 1998), but meningiomas and lymphomas are the most frequent when found
(Zaki and Hurvitz, 1976;
Parker et al., 1983). There are two reports of primary spinal cord gemistocytic astrocytoma in
felines (Aloisio et al., 2008; Marioni-Henry
et al., 2008), and this is the first case
report from South America.
Gemistocytic
astrocytomas are variants of diffuse astrocytomas characterized by the presence of gemistocytic astrocytes (Martins
et al., 2001; Avninder et al., 2006). The gemistocytes are characterized by abundant, glassy eosinophilic cytoplasm and eccentrically placed nuclei.
These cells are not present in normal tissue or during embryogenesis of the CNS
(Kros et al., 1991; Avninder
et al., 2006).
According to the WHO’s
classification system for humans, gemistocytic astrocytomas are characterized by the presence of a
conspicuous, though variable, fraction of gemistocytic
astrocytes and are classified as grade II (Kleihues et al., 2002), but the percentage of gemistocytic cells necessary to classify a gemistocytic astrocytoma as a
tumor is not specified. Some reports propose that at least 20% of gemistocytic astrocytes should be
present in a human CNS tumor to classify it as a gemistocytic
astrocytoma (Krouwer et
al., 1991; Avninder et al., 2006). In the veterinary
literature, no reports about the use of the gemistocytic
index to classify a tumor as gemistocytic astrocytoma were found because was no used it so far.
The definitive diagnosis of a spinal
cord tumor can be achieved only after histopathological
analysis (LeCouteur and Grandy,
2005), and the immunohistochemical assay has become
an indispensable technique for confirmatory diagnosis (Koestner
and Higgins, 2002). This report is important since it describes the clinical,
radiological, pathological and immunohistochemical
findings associated with this tumor in a cat; comparative aspects in human
beings are also discussed.
CASE REPORT
A six-year-old, intact male Siamese
cat was admitted to the Veterinary Hospital, Universidade
Estadual de Londrina, Londrina/PR, Southern
Brazil. The animal had a history of progressive hemiparesis,
muscle atrophy in the right thoracic limb and pain in this region for
approximately five weeks. Clinical and neurological examinations led to the
diagnosis of spinal cord dysfunction. Increased reflexes, hyperesthesia and propioceptive deficit were observed in the right thoracic
limb. Plain radiography was performed, with no alteration. Medical therapy was
initiated, but neurological signs were progressive and severe, affecting the
pelvic limbs, which showed increased reflexes, propioceptive
deficit and spastic paresis. Seven days after the initial examination, the
owner opted for euthanasia. Routine necropsy was performed soon after death;
selected tissues (brain, spinal cord, lung, kidneys, liver, heart, and spleen)
were fixed in 10% buffered formalin solution and routinely processed for histopathological evaluation. Sections were stained with hematoxylin-eosin (HE) and periodic acid Schiff (PAS). The gemistocytic index was quantified by counting 200 cells in
five different fields under 40x magnification and calculating the average
number of gemistocytic cells.
Selected paraffin-embedded tissue
fragments from the spinal cord were prepared for immunohistochemical
(IHC) analysis. Immunostaining was performed using a
polymer-based detection kit. Slides were incubated with one of five primary
antibodies: GFAP, vimentin, macrophage antigens (lysozyme and LN-5) or S100 protein. For IHC, the polymer-peroxidase technique was used. Antibody dilution and
incubation time followed the manufacturer’s recommendations. The color reaction
to detect the antigen was carried out with 3,39-diaminobenzidine.
Tissue fragments from nervous tissue, lymph nodes, and breast were used as
positive controls; for negative controls, mouse serum substituted the primary
antibody.
Gross examination showed a intramedullary swollen area in
the C6 region of the spinal cord. After fixation, the spinal cord was cut,
revealing a well-delimited, whitish and soft area in the right lateral region
of the C6 segment (Figure 1). The affected region comprises the lateral funiculus. The histopathology exam showed diffuse
proliferation of large cells with distinct borders, abundant eosinophilic cytoplasm and eccentrically located large
nuclei with prominent nucleoli (Figure 2, 3, 4). Glial
fibers were scarce, atypia was moderate and mitotic
index was low. The average gemistocytic index was
72.2%. The PAS method showed no staining of the granules within the cytoplasm
of neoplastic cells. The immunohistochemical
assay showed positive GFAP
(Figure 5), staining for S100 and
vimentin (Figure 6) and negative staining for lysozyme and LN-5 (macrophage) was showed in table 1. Based
on histopathological and immunohistochemical
features , the diagnosis of gemistocytic
astrocytoma was made.
DISCUSSION
Tumors of the central nervous system
are common in humans and constitute the second most prevalent type of tumor in
childhood (Wilson et al., 2002). Glial tumors are
among the most common primary tumors of the central nervous system in humans (Rasheed and Bigner, 1997; Balmaceda et al., 2002), dogs and cats (Koestner
and Higgins, 2002).
Astrocytoma is the
most common glial tumor in canines (Maxie and Youssef, 2007) and is
most frequently diagnosed in brachycephalic breeds,
such as Boston Terriers and Boxers ( S’antana et al.,
2002), with greater incidence in animals over five years of age (Storts 1995; Stoica et al., 2004;
Zachary, 2007). In the cat, astrocytomas are uncommon
and when discovered, are most frequent in cats over nine years of age (Santana
et al., 2002; Henry et al., 2008). Some
reports demonstrate that the occurrence of astrocytomas
in dogs and cats can be related to genetic alterations such as inactivation of
p53 and overexpression of EGFRP (Stoica
et al., 2004; Stoica et al., 2009).
The spinal cord can be invaded or
compressed by primary or metastatic neoplasias
arising from the vertebral column and surrounding structures. Primary neural
tumors include ependymoma, glioma,
neurofibroma, neurofibrosarcoma,
schwannoma, meningioma, meningeal sarcoma, neuroepithelioma,
reticulum cell sarcoma and astrocytoma (LeCouteur and Grandy, 2005).
In children, spinal cord tumors
represent 1-10% of all tumors of the central nervous system (Wilson et al.,
2007), and intramedullar spinal cord astrocytomas represent 6-8% of all spinal cord tumors (Minehan et al., 2008). In animals, intramedullar
neoplasia of the spinal cord is less common than the extramedullar form (DeLahunta,
1983). In general, extradural, intradural-extramedullar
and intramedullar tumors cannot be distinguished on
the basis of clinical signs (Luttgen et al., 1980; DeLahunta, 1983, LeCouteur and Grandy, 2005). Intramedullar
tumors are reported to cause a more rapid progression of clinical signs and to
be much less likely to be painful than extradural or intradural-extramedullary tumors (LeCouteur
and Grandy, 2005).
The clinical signs depend on the
location of the tumor in the spinal cord and also on whether more than one
segment is involved. Compressive lesions within the cervical portion of the
vertebral canal often cause cervical hyperesthesia and minimal or no
neurological deficits because of the relatively larger
diameter of the cervical portion of the vertebral canal compared with the
diameters of the thoracic and lumbar regions. Intramedullar
spinal cord tumors, such as astrocytomas, usually
hasten neurological dysfunction (LeCouteur and Withrow, 2007) and are less amenable to surgical removal (DeLahunta, 1983).
The cat showed neurological signs compatible with a lesion of an upper
motor neuron (DeLahunta, 1983), such as progressive
muscle atrophy from disuse, increased reflexes, hyperesthesia and propioceptive deficits. The tumor did not affect the nerve
root because the cat did not show signs of lower motor neuron lesion. The tumor
had a continuous progression, and the meninges were
compressed, causing painful increased sensitivity in the right thoracic limb.
The complementary techniques used to
confirm the presence of neoplasia in the spinal cord
are plain radiography, cerebrospinal fluid analysis (CSF), myelography
and specialized radiographic techniques such as computerized tomography and
magnetic resonance imaging (Parker et al., 1983; Wheeler et al., 1985; LeCouteur and Grandy, 2005).
Plain radiography did not show evidence of intramedullary
spinal tumor (Wright et al., 1979; Fenner, 1994), but
myelography may be helpful in differentiating intramedullar, intradural-extramedullar
and extradural neoplasia (LeCouteur and Grandy, 2005). In
this case, no alteration was evidenced on plain radiography. Due to the cat’s
rapid progression of clinical signs and increased pain, the owner opted for
euthanasia, and no further imaging examination was performed.
A definitive diagnosis of nervous
tumors is possible through only histopathological
examination. However, immunohistochemical assay has
become an indispensable technique to confirm diagnosis and to classify nervous
system tumors (Barnhart et al., 2002; Koestner and
Higgins, 2002). The histopathological classification
of the CNS tumors in animals is primarily based on cell type, pathological
behavior, topographic pattern and secondary changes present within and
surrounding the tumor (LeCouteur and Withrow, 2007).
The presence of gemistocytic
astrocytes in CNS tumors is considered a marker of
poor prognosis, as these cells are not present in normal tissue. However, their
role remains unknown. The gemistocytic index in this
case was 72.2%, far higher than the percentage found in the human gemistocytic astrocytoma (Krouwer et al., 1991; Avninder et
al., 2006). This value demonstrates that gemistocytic
astrocytoma can be more aggressive in cats than in
humans. Gemistocytic astrocytoma
exhibits a tendency toward aggressive clinical behavior due to its increased
propensity for recurrence and rapid progression to glioblastoma
(Burton and Prados, 2000; Aloisio
et al., 2008).
An important differential diagnosis
is granular cell astrocytoma, which shows histological
findings similar to gemistocytic astrocytoma.
Large round to oval cells with distinct borders and abundant eosinophilic granular cytoplasm characterize granular cell astrocytoma (Higgins et al., 2001; Shi and Morgenstern,
2008). PAS staining can be used to
demonstrate the presence of granules within the cytoplasm. In this case, the
tumor was negative for PAS staining. Positive staining for S100 protein and vimentin and negative staining for GFAP were reported in
granular cell tumors (Higgins et al., 2001; Mandara
et al., 2006). The immunohistochemical procedure was
performed using antibodies against lysozyme and LN-5
to rule out a tumor of monocyte/histiocyte
phenotype. On the other hand, the positive immunostaining
for S100, vimentin and GFAP indicated that the tumor
had an astrocytic derivation. The histological and immunohistochemical findings are in accordance with the
characteristics described in the literature for gemistocytic
astrocytoma (Summers et al., 1995; Avninder et al.,
2006; Baena et al., 2007).
The prognosis of animals with tumors
of the CNS depends on tumor location, surgical accessibility, growth and degree
of damage to the nervous system (DeLahunta, 1983).
The prognosis for feline with intramedullary spinal cord astrocytoma
is poor, as this condition has a relentlessly progressive course (Fenner, 1994; Jeffery and Phillips, 1995). Clinical signs
and laboratory and imaging exams generally do not yield conclusive diagnoses. Histopathological and immunohistochemical
methods are fundamental for the definitive diagnosis and classification of intramedullary spinal cord tumors.
In conclusion, gemistocytic
astrocytoma was diagnosed and confirmed in this cat
due to the characteristic histopathological and immunohistochemical findings that are consistent with this neoplasia. This report contains information that would be
useful to assist pathologist and veterinarians in the diagnosis and
understanding of this uncommon disease entity in feline.