Keywords
sarcoma, Ewing - pelvic neoplasms - eosinophilic granuloma - osteomyelitis - anti-onflammatory
agents, non-steroidal
Introduction
Ewing sarcoma (ES) is a primary bone tumor. In > 50% of cases, a soft tissue component
is associated.[1] Ewing sarcoma is rare, with an annual incidence of 2.93 per million individuals.[2]
[3] Amongst the bone tumors, it is one of the most lethal, with high propensity for
recurrence and distant metastasis (predominantly to the lungs). Generally, it affects
the diaphysis and metaphysis of long bones.[4]
[5] It is rare in patients > 30 years old, with 90% of the cases affecting individuals < 20
years old.[4] In this age group, it is the most common pelvic tumor. The prognosis of pelvic ES
is poor, with a 5-year survival rate of 50%.[6] Its most common symptoms are night pain (90%) and swelling (70%), the latter of
difficult assessment in pelvic ES. Fever, weight loss, anemia and increased inflammatory
markers are uncommon unspecific manifestations.[1]
[7]
[8] Radiographs feature lytic destruction and subperiosteal bone formation similar to
“onion skinning.”[1]
[4]
[5]
[8] These features are most easily detected in long bones in comparison with the pelvis.
The value of radiographs in the pelvis is compromised by the anatomy of the iliac
bone and of overlying structures.[1]
[8] Computed tomography (CT) allows a better assessment of bone destruction and may
show a soft tissue component.[1]
[5] Early magnetic resonance imaging (MRI) for soft tissue characterization and, to
a lesser extent, identification of a “sharp transition zone”, is useful.[3]
[7] These nonspecific clinical and imagiological findings may be present in conditions
such as metastatic carcinoma, malignant lymphoma, osteomyelitis,[4] fibrous dysplasia[5] or eosinophilic granuloma (EG),[9] making its early diagnosis challenging.[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9] The definitive diagnosis is made by open biopsy and histological examination combined
with immunochemistry and cytogenetics.[1]
[4] The lack or insufficiency of histologic specimens by percutaneous biopsy may lead
to its misdiagnosis.[2]
[4] We report two cases of ES that attended our department in the last 3 years, the
first mimicking EG and the second osteomyelitis. Our purpose is to highlight pitfalls
on the diagnosis of pelvic ES and to report an atypical finding of its natural history:
an initial response to antibiotic and anti-inflammatory treatment, only described
once in the literature.[4]
Case Report 2
A 30-year-old man, with former history of syphilis and drug addiction, presented to
our emergency department with a 1-month history of right inguinal pain without constitutional
symptoms. Blood tests demonstrated an elevated white cell count (15.9 × 109 cells/L) and increased C-reactive-protein (104 mg/L). Hemoglobin and erythrocyte
sedimentation rate were normal. Radiographs were inconclusive ([Fig. 4A]). Computed tomography and MRI findings were consistent with an inflammatory lesion
involving the right ischiopubic ramus and obturator muscles, with an associated abscess,
making the diagnosis of osteomyelitis most likely ([Figs. 4B] and [5A]). Due to fever onset and increasing inflammatory markers, empiric antibiotic therapy
was started (intravenous ceftriaxone, 2 g/day). Prior to the antibiotic therapy, blood
cultures were collected and a percutaneous drainage was performed, but no agent was
isolated. The patient responded well to the antibiotic and anti-inflammatory treatment
with fever and pain resolution. Following 15 days of treatment, there was a considerable
decrease on white cell count (11.5 × 109 cells/L) and C-reactive-protein (18.0 mg/L). However, an MRI showed persistency of
the lesion ([Fig. 5B]). The patient was submitted to an excisional biopsy. The histopathological examination
was consistent with ES, and was later confirmed by immunochemistry and cytogenetics.
The patient was transferred to a specialized center.
Fig. 4 Inconclusive radiograph on admission (A) and computed tomography scan showing enlargement of the right obturator muscles
(B).
Fig. 5 Initial magnetic resonance imaging showing a lesion involving the right ischiopubic
ramus and obturator muscles (A) and magnetic resonance imaging following antibiotic treatment showing persistency
of the lesion (B).
Discussion
Ewing sarcoma may raise suspicion for malignancy in young adults when it involves
long bones in a typical location with associated pain and palpable soft tissue mass.[5] In the pelvis, the latter is difficult and, therefore, constitutional symptoms should
not be overlooked. On the other hand, EG, a benign tumor-like condition, commonly
affects flat bones. Radiologically, acute phase EG shows osteolysis with poorly defined
margins similar to ES. On MRI, bone marrow involvement and an associated soft tissue
component may also be present. Since imagiological features are similar, lesion biopsy
is indispensable for the correct diagnosis.[9] In case 1, samples collected by percutaneous biopsy were not representative, leading
to the misdiagnosis of EG. Therefore, when clinical and imagiological features are
consistent with ES, a negative percutaneous biopsy should not rule it out, and an
excisional biopsy should be performed. To minimize diagnostic errors and contamination
of biopsy pathways, biopsies should be performed by surgeons with expertise in bone
tumors.[10]
In case 2, the presentation was atypical. The age, previous medical history, imagiological
and biochemical findings were consistent with osteomyelitis. The sterility of the
biopsy and blood cultures did not exclude its diagnosis, since as many as 26% of cases
of osteomyelitis are diagnosed without culture confirmation and are supported retrospectively
by their resolution following antibiotic therapy.[4] Moreover, our patient responded to the antibiotic and anti-inflammatory treatment.
This response may be explained by the association of elevated levels of arachidonic
acid metabolites and prostaglandins to malignancies. Inhibition of the arachidonic
acid pathway by antibiotic and nonsteroidal anti-inflammatory agents may have modulated
the clinical symptoms and tumor growth.[4]
Conclusions
The diagnosis of ES should not be overlooked in the assessment of pelvic lesions,
and exclusion diagnosis should be the rule. If clinical and imagiological features
are consistent with its diagnosis, a negative percutaneous biopsy should not rule
it out, and an excisional biopsy should be performed. If clinical and imagiological
features are consistent with osteomyelitis, an initial response to antibiotic and
anti-inflammatory therapy does not allow its exclusion, with watchful waiting being
recommended.
