Open Journal of Orthopedics, 2011, 1, 5-8
doi:10.4236/ojo.2011.12002 Published Online December 2011 (http://www.SciRP.org/journal/ojo)
1
Eosinophilic Granuloma Arising from the Sacrum:
A Case Report
Yuji Kasukawa, Naohisa Miyakoshi, Michio Hongo, Shigeru Ando, Yoshinori Ishikawa,
Yoichi Shimada
Department of Orthopedic Surgery, Akita University Graduate School of Medicine, Akita, Japan.
Received October 4th, 2011; revised November 13th, 2011; accepted November 26th, 2011.
ABSTRACT
Introduction: Osseous eosinophilic granulomas commonly occur in the skull, pelvis, vertebrae, mandible, and ribs.
However, the eosinophilic granuloma in the sacrum is rare. Case presentation: We present the case of a 13-year-old
Japanese boy, who presented with left low-back pain, and was diagnosed with eosinophilic granuloma arising in the
sacrum. Computed tomography (CT) and magnetic resonance imaging demonstra ted an osteolytic lesion with interrup-
tion of the cortex, and signal intensity changes at the left sacral body and wing. Histologic examination indicated an
eosinophilic granuloma. Two years after CT-guided biopsy, the tumor had spontaneously healed completely, with no
residual pain. Conclusion: The present ca se was eo sioph ilic gr anu loma aris ing from the rare site o f sacru m . The tumor
was completely remodeled two years after biopsy.
Keywords: Eosinophilic granuloma, Sacrum, Biopsy
1. Introduction
Eosinophilic granuloma is a benign tumor-like condition
characterized by a clonal proliferation of Langerhans-typ e
histiocytes in the bone or lung [1,2]. Eosinophilic granu-
loma of bone was initially described in 1940 [3,4], and
its reported incidence is currently 0.05 - 0.5 per 100,000
children per year, with 90% of tumors occurring under
the age of 15 years [5-9]. Regarding the location of os-
seous eosinophilic granulomas, the flat bones are in-
volved in 70% of tumors, and the long bones in 30% [10].
Among the flat bones, eosinoph ilic granulomas predomi-
nantly affect the skull, pelvis, vertebrae, mandible, and
ribs [1,8]. However, to the best of our knowledge, only
one report has previously described this type of tumor in
the sacrum [11]. We describe here a case of eosinophilic
granuloma of the sacrum, which spontaneously healed
completely after biopsy.
2. Case Report
A 13-year-old boy had a 2-month history of left low-
back and buttock pain. He was referred to our institution
when magnetic resonance imaging (MRI) at another hos-
pital revealed abnormal changes in the sacrum. His left
low-back and buttock pain was increased by lumbar ex-
tension. Neurologic examination on admission was nor-
mal. Plain radiography showed an osteolytic change in
the left sacral wing and sacral vertebral body (Figure
1(a)). Computed tomography (CT) images showed oste-
olytic low-density changes in th e left sacral vertebral bo-
dy extending to the sacral wing and sacro-iliac join t, with
sclerotic changes around the osteo lytic lesion. The cortex
of the sacrum was interrupted at the sacro-iliac joint and
the osteolytic lesion had a partly sclerotic margin (Fig-
ure 1(b)). MRI revealed slight high-intensity changes
compared to muscle tissue on T1 weighted images, with
strong uniform enhancement by gadolinium and non-
uniform intensity changes on T2 weighted images (Fig-
ure 2). A technetium-99 m bone scan revealed uptake at
the S1 vertebral body (Figure 3(a)). Based on these ex-
aminations, a malignant tumor such as Ewing’s sarcoma
or chronic osteomyelitis was considered as a differential
diagnosis. Needle biopsy was performed under CT guid-
ance through a posterior approach (Figure 3(b)). His-
tologic examination demonstrated mixed and dense cel-
lular infiltrate including histiocytes with mildly irregular
cell nuclei, eosinophils, neutrophils, and lymphocytes
(Figure 3(c)). Histiocytes stained positive for CD68,
which is found in the cytoplasmic granules and useful in
diagnosing histiocytic diseases, on immunohistochemical
staining (Figure 3(d)). These histologic findings led to a
diagnosis of eosinophilic granuloma. The patient’s pain

Eosinophilic Granuloma Arising from the Sacrum: A Case Report
6
(a) (b)
Figure 1. Plain radiograph and CT image before biopsy. (a) Anteroposterior plain radiograph of sacrum showing slightly
defined osteolytic lesion on the left sacral wing (small arrows); (b) Axial CT demonstrates an osteolytic lesion with a partly
sclerotic margin in the sacral body and the left sacral wing.
(a) (b) (c)
Figure 2. MRI of before biopsy.Lesion shows reduced signal intensity, which is isointense with muscle, in the axial T1-
weighted image (a) and is well-enhanced by gadolinium; (b) In the axial T2-weighted image; (c) the lesion has slightly higher
intensity than the bone marrow of the ilium.
100 m 100 m
(a) (b) (c) (d)
Figure 3. Bone scan before biopsy, CT image during biopsy, and histology. (a) Bone scan with technetium-99m showing in-
creased uptake in the left sacral body and sacral wing. (b) Axial CT image during biopsy of the osteolytic lesion in the sacral
wing. (c) Histologic examination demonstrating mixed and dense cellular infiltrate including histiocytes with mildly irregular
cell nuclei (arrows), eosinophils, neutrophils, and lymphocytes. (d) Immunohistochemical staining showing CD68-positive
staining of histiocytes.
gradually subsided following CT-guided biopsy, and CT
and MRI images 3 months after biopsy showed an obvi-
ous decrease in the size of the osteolytic lesion. Two
years after biopsy, his pain had completely disappeared,
and the osteolytic lesion was not visible in CT images
(Figure 4(a)), and appeared to be remodeled with fatty
marrow in MR images (Figures 4(b) and 4(c)). Written
informed consent was obtained from the patient for pub-
lication of this case report and accompanying images. A
copy of the written con sent is available for rev iew by the
Editor-in-Chief of this journal.
3. Discussion
The osseous lesions of eosinophilic granulomas appear
as osteolytic, modestly destructive lesions of a flat bone,
including the skull, mandible, ribs, and pelvis, in about
50% of cases [7]. Supraacetabular lesions represent the
most common site of this tumor in the pelvis [12]. The
iliac wings, iliac bone adjacent to the sacro-iliac joint,
and the ischiopubic rami are other common sites for pel-
vic eosinophilic granulomas [12]. Eosinophilic granulo-
mas occurring in the spine usually involve the vertebral
body [6,12], showing charact eristi c symm etrical flat tening

Eosinophilic Granuloma Arising from the Sacrum: A Case Report7
(a) (b) (c)
Figure 4. MRI and CT images two years after biopsy. (a) Axial CT image 2 years after biopsy demonstrating remodeled tra-
becular bone in the sacral body and wing, without interruption of cortex. The lesion demonstrated higher intensity compared
to normal bone marrow in the axial T1-weighted (b) and T2-weighted images (c) 2 years after biopsy.
of the vertebra, known as “vertebra plana”. The thoracic
spine is the most common site, followed by the lumbar
and cervical spine, respectively [6,12]. To the best of our
knowledge, the present patient represents the first re-
ported case of eosinophilic granuloma in the sacrum.
Although eosinophilic granuloma bone lesions are u-
sually asymptomatic, osteolytic lesions sometimes cause
fractures or pain as a result of swelling, deformity, and
soft tissue components [6]. The chief complaint in the
current case was low-back pain; however, the osteolytic
lesion in the sacrum was poorly defined by plain radiog-
raphy. MRI of the lumbar spine, however, revealed in-
tensity changes in the sacrum. MRI thus provides a
highly sensitive, but nonspecific, modality for detecting
bone marrow involvement and soft tissue mass in eosi-
nophilic granulomas [8].
Eosinophilic granulomas can be divided in to acute and
chronic phases, depending on their status [6,8]. Th e acute
phase includes destructive, osteolytic lesions with poor
margins, which are difficult to differentiate from malig-
nant tumors such as Ewing’s sarcoma, or acute osteo-
myelitis [8]. CT is useful for evaluating osseous eosino-
philic granuloma lesions, and for determining the extent
of cortical destruction and soft tissue involvement [8].
CT-guided biopsy is also useful for diagnosing eosino-
philic granuloma as a cause of vertebral osteolysis or
vertebra plana [9], and was helpful for diagnosing eosi-
nophilic granuloma in the sacrum with cortical destruc-
tion in the present case.
Treatment options include aggressive resection, biopsy,
combined chemotherapy and radiotherapy, and conserva-
tive treatment. Radiation therapy is associated with a risk
of secondary malignancy [13] as well as effects on the
pelvic viscera, and should be avoided, especially in chil-
dren, because it may destroy the growth potential of the
endochondral plates [14,15]. Ando et al. reported eosi-
nophilic granulomas in the pelvis with different radi-
ologic features and clinical courses [16]. They reported
that osteolytic t umor lesions with sclerotic ma rgins he ale d
spontaneously after b iopsy, while tumors with poor oste-
olytic margins progressed after biopsy. The present case
was consistent with this prev ious report in that p art of th e
osteolytic lesion in the sacrum rev ealed sclerotic margins
on CT, and subsequently spontaneously healed comple-
tely. Surgical treatment, especially in adolescents, should
be reserved for specific cases with neurologic defects or
instability.
4. Conclusions
In conclusion, this patient represents the case of eosino-
philic granuloma arising in the rare site of sacrum, which
spontaneously and completely healed 2 years after biopsy.
Biopsy is a better choice to decide a therapeutic strategy
of the osteolytic tumor in the sacrum. If the tumor is
eosinophilic granuloma, the tumor has a chance to heal
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