Keywords
primary Ewing's sarcoma - round cell tumor - frontoparietal bone
Introduction
Primary Ewing's sarcoma arising from the skull is very rare although it is the second
most common tumor in the children. The skull is involved in less than 2% cases, and
it most commonly originates from bone and soft tissues of the extremities and pelvis.[1]
[2] Recently we came across a large painless primary Ewing's sarcoma arising from frontoparietal
bone with good survival, hence being reported.
Case Report
A 17-year-old man presented with a swelling in the frontal region of 6 months duration,
which started increasing in size during the previous 3 months. There was no history
of pain in the swelling, headache, vomiting, or fever. There was no history of loss
of weight or appetite. There was no history of trauma. On examination, the patient
was fully conscious, alert, and oriented with no focal neurologic deficits. The fundus
was normal. There was a 15- × 16-cm-sized swelling in the bifrontal region. Swelling
was firm in overall consistency and a soft portion in the posterolateral area. Overlying
skin was free. There was no visible pulsation or bruit. Swelling was nontender, and
the temperature over it was normal.
Three-dimensional computed tomographic (3D CT) reconstruction image revealed multiple
osteolytic areas ([Fig. 1A]). Contrast CT revealed an enhancing osteolytic soft tissue mass in the frontoparietal
area ([Fig. 1B–D]). Fine-needle aspiration cytology (FNAC) was reported to be a round cell sarcoma.
At surgery, the lesion was found to be soft, fleshy, mildly vascular, and easily separable
from the dura. Wide excision of the tumor and surrounding bone was done, and healthy
dura was seen peripheral to the tumor. Dura was not excised. There was no involvement
of the superior sagittal sinus. Postoperative 3D CT reconstruction showed wide craniectomy
([Fig. 1E]). Histopathology revealed it to be round cell sarcoma, and immunohistochemistry
confirmed it to be Ewing's sarcoma. Immunohistochemistry revealed positivity for vimentin,
CD3, CD20, and CD60 in some cells. The cells were negative for HMB-45 and S100. The
patient was given local radiation of 45 Gy and chemotherapy consisting of vincristine,
cyclophosphamide, and cisplatin, ifosfamide, etoposide, and Adriamycin. He is currently
doing well at 60 months follow-up. A hard underlying membrane formed in the area of
craniectomy after approximately 3 years. The patient was offered cranioplasty on various
occasions at follow-up, but he refused. Repeated positron emission tomography (PET)
scan during follow-up has revealed no evidence of recurrence of tumor ([Fig. 1F]).
Fig. 1 (A, B) Preoperative plain and post contrast images showing bone destruction with soft tissue
homogenous enhancing mass. (C) CT lateral view showing patent sagittal sinus and epidural soft tissue mass with
intact dura. (D) Preoperative 3D CT reconstruction image showing multiple osteolytic areas. (E) Postoperative 3D CT reconstruction showing wide craniectomy. (F) PET scan showing no recurrence at operative margins.
Discussion
Primary Ewing's sarcoma is a highly malignant bone tumor. It is a member of Ewing's
sarcoma family of tumors (ESFT), others being primitive neuroectodermal tumor, Askin's
tumor, and extraosseous Ewing's sarcoma. These tumors are more commonly seen in young
and adolescents and are characterized by small and round cells.[3]
[4]
Our patient presented with swelling without any symptoms and signs of raised intracranial
pressure or neurologic involvement. The temporal bone is most commonly involved followed
by parietal, occipital, sphenoid, and ethmoid in that order.[5]
Plain X-ray usually shows bone destruction, with irregular poorly defined margins.
CT usually shows isodense lesion with marked heterogonous enhancement. Magnetic resonance
imaging (MRI) shows well-defined lobulated extra-axial mass lesion with mixed intensity
signals on both T1 and T2 W images.[6] FNAC and biopsy are essential to reach a diagnosis, but definitive diagnosis is
reached by immunohistochemistry. Differential diagnosis of such lesion includes metastatic
neuroblastoma, rhabdomyosarcoma, osteosarcoma, and meningioma.
Treatment of Ewing's sarcoma is multimodal. It includes surgery, radiotherapy, and
repeated courses of chemotherapy consisting of ifosfamide, cisplatin, etoposide, and
Adriamycin. Our patient is symptom free for the past 60 months, and the repeat PET
scan has been negative for local or distant recurrence. Primary Ewing's sarcoma of
the skull has been known to metastasize to the lungs and bone. Duration of symptoms
of longer than 6 months, absence of fever or systemic symptoms, peripheral location
and absence of metastasis, leukocyte count of < 7,000/dL, and lymphocyte count of
< 2,000/dL indicate a good outcome.[7]
[8]
[9]
Primary Ewing's sarcoma of the skull vault has relatively good prognosis because it
can be totally or subtotally excised with wide margins. However, sarcomas arising
from the skull base by involving vital structures preclude surgical excision.
To conclude, primary cranial Ewing's sarcoma should be considered in the differential
diagnosis in adolescence with tumor involving the skull with destruction of bone and
presence of extracranial soft tissue mass.
