Discussion
Ewing’s sarcoma remains an enigmatic and particular malignant tumor 100
years after its discovery. Spinal involvement most commonly results from
metastasis in advanced stages of the disease, while EWS originating from
the spine is rare and extremely rare if the sacrum is excluded
[2,3]. Diagnosis could be quite difficult due to an insidious onset,
non-specific symptoms and misinterpreted images. Thus, symptoms may not
be present until neurological deficits occur and diagnosis suspicion may
be after several consultations which increase doubts [7,8]. The
average delay from the onset of symptoms to the diagnosis has been
reported to be 34 weeks all locations combined [9]. In our case the
delay was 48 weeks. That’s why approximately 25% of patients present
with metastatic disease at diagnosis; fortunately this was not the case
of our patient [3].
Definitive diagnosis requires cytological, immunohistochemical (CD99)
and cytogenetic analysis of a pathologic specimen. The translocation
involving chromosome 22 is identified in more than 90% of cases, and it
is the landmark to differentiate EWS from other small, round blue cell
tumors [3,10].
Currently, early diagnosis and multimodal treatment combining surgery,
chemotherapy, and local radiation therapy increases the chance of a
successful outcome [11]. Indelicato et al [12], in a review have
reported a five-year overall survival rate of 71% and local control
rate of 89% for non-metastatic spinal and paraspinal EWS. However, when
compared to other sites of occurrence, prognosis of EWS of the spine
remains worse [13].
Initial chemotherapy and local radiotherapy might be administered before
surgery with the aim to shrink bulky and unresectable tumors, to
eradicate micrometastases and for acute relief of epidural compression,
but it should be noted that there is a variable sensitivity to radiation
and chemotherapy due to biological heterogenecity [1].
During the last two decades, the outcome in patients with localized
disease has improved through an aggressive surgery known as en bloc
vertebrectomy by combining anterior and posterior approach or from a
single posterior approach as described by Tomita and al [14].
Boriani et al [6] described three major methods of performing en
bloc excisions in the thoracolumbar spine: vertebrectomy if the tumor is
confined to zones 4 to 8 or 5 to 9; sagittal resection when the tumor
occupies zones 3 to 5 or 8 to 10 and resection of the posterior arch
when it is located between the zones 10 and 3 according to their
surgical staging system.
However, en bloc resection is a highly demanding procedure that must be
carefully planned and the greater surgical risk can be accepted only if
it offers a safer result and is performed by specialized surgical and
anesthesiology teams [5].
Among the difficulties to be considered is the release of the spinal
cord if the tumor is expanding to layer D according to WBB staging
system. In this case theoretical safe margin should include the dura in
the resection specimen but the cost-to-benefit ratio of such procedure
should be carefully evaluated. Boriani and his collaborators have shown
that a simple release of the dura without resection can be accepted and
without proven consequence on the risk of recurrence [6,13].
Compared to cases where only decompression or lesionectomy was done,
patients who underwent en bloc spondylectomy had a lower recurrence rate
[8,15]. This is why, whenever possible, surgical en bloc wide
resection with an anterior column reconstruction is preferable in order
to obtain a better oncological control and a better preservation of the
spine biomechanics [3].