Ewing’s sarcoma of pelvis with intracranial dural metastases

INTRODUCTION

Primary Ewing’s sarcoma of bone is an aggressive malignancy with a high rate of metastases. The management includes systemic chemotherapy along with local control through surgical resection and/or radiotherapy. The pelvic bone is involved in nearly 25% of cases; the prognosis of Ewing’s sarcoma of the pelvis is worse with a reported 5-year survival rate of nearly 50%.^[1] Primary or metastatic intracranial Ewing’s sarcoma is rare with a reported incidence of 1.2% for primary and 0.3% for metastatic intracranial lesions from extracranial Ewing’s sarcoma. Only three cases of intracranial dural metastases with Ewing’s sarcoma have been reported in the literature to date. We report another case of Ewing’s sarcoma of the pelvis with dural metastases and review the present literature.

CASE REPORT

A 25-year-old man presented with a history of pain in his left hip, radiating along the entire leg. He reported no systemic symptoms but reported significant weight loss. He has no other co-morbidities and his general physical and neurological examination was normal. X-ray of the pelvis showed a lytic lesion involving the left superior and inferior pubic rami and ischial tuberosity [Figure 1a]. The whole body fludeoxyglucose (FDG) positron emission tomography (PET) revealed an FDG-avid lytic lesion associated with soft tissue components in the left pubic bone, ischium, ischiopubic ramus, and acetabulum. Two small 5-mm lung nodules were noted. A magnetic resonance imaging (MRI) of the pelvis showed a 9.5 × 6.6 × 8.1 cm soft tissue lesion in the left pelvic bones. A primary bone malignancy was suspected, and a gun biopsy of the lesion was done. The histopathology was suggestive of malignant round-cell tumors in diffuse sheets and clusters with hyperchromatic nuclei, inconspicuous nucleoli, and scanty cytoplasm. Tumor cells were positive for MiC-2, synaptophysin, friend leukemia integration 1 transcription factor, and NKX2.2 and negative for desmin and terminal deoxynucleotidyl transferase. The histopathology was suggestive of Ewing’s sarcoma.

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Figure 1:

(a) X-ray of the pelvis showing a lytic lesion involving left superior and inferior pubic rami and ischial tuberosity (arrow) and (b) fludeoxyglucose positron emission tomography showing metabolically active lesion in the L1 vertebra (circle and arrow) and (c) the 8^th rib (square and arrow) suggestive of metastases.

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The patient received three cycles of chemotherapy with ifosfamide and etoposide, vincristine, actinomycin D, and cyclophosphamide followed by radiotherapy in the pelvis and both the lungs followed by another four cycles of chemotherapy. The patient continued to have left hip and leg pain. A second radiation cycle was given. Repeat FDG PET showed new increased metabolically active lesions in the left femur shaft in the medullary cavity, L1 vertebra, and right 8^th rib anterior end [Figure 1b and c] suggestive of metastatic lesions. The patient was started on chemotherapy with irinotecan and temozolomide. He also received radiotherapy for the vertebrae.

Two years into the disease, he reported a new onset right hemicranial and bi-frontal headache of 1-month duration, present throughout the day, not interfering with sleep. The headache was not associated with vomiting, photophobia, or phonophobia. His fundus examination and neurological examination were normal. He had no meningeal signs. The MRI brain showed a right basiocciput bony deposit suggestive of metastasis [Figure 2a]; another dural-based hypointense lesion, measuring 24 × 7 mm in size, was noted in the right frontal region with homogeneous intense enhancement of margins and an intense dural enhancement of the right fronto-parietal cortex suggestive of dural metastatic deposits [Figure 2b-d]. The headache responded to analgesics. The patient did not consent to the biopsy of the cranial lesion after understanding the limited options available in the management and prognosis of his advanced disease and few months later succumbed to the illness.

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Figure 2:

Magnetic resonance imaging brain – (a) fluid-attenuated inversion recovery (FLAIR) axial images showing the right basi-occiput metastatic bony deposit (arrow), (b) FLAIR axial image showing right frontal dural-based lesion (arrow), (c) diffuse dural enhancement in the right frontoparietal cortex (arrows), (d) right frontal dural based hypo intense lesion with contrast enhancement of the margins suggestive of dural metastases (arrow).

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DISCUSSION

Intracranial metastases of Ewing’s sarcoma are rare at a reported incidence of 0.3% and occur either by direct extension from the skull primary lesions or through hematogenous spread from extra-cranial sites.^[2] The overall survival is lower in patients with intracranial metastases when compared to localized disease with a reported survival rate of 28% at 3 years.^[3] Most of the cases reported had involvement of the bony calvarium or the brain parenchyma. Dural metastases in Ewing’s sarcoma are rare and only three cases have been reported to date. We report an additional case of Ewing’s sarcoma of the pelvis with dural metastases.

Dural metastases account for 9% of all the central nervous system metastases.^[4] The first case of dural metastases of Ewing’s sarcoma was reported by Kleinschmidt-DeMasters in 2001 surgery and autopsy series where he described dural involvement was associated with a massive epidural plaque-like nodule.^[5] The second case was reported in 2008 by Kim et al., in a 21-year-old woman^[6] where the lesion was a cerebellopontine angle mass lesion and later it was considered a metastatic tumor because of the appearance of a new contrast-enhancing lesion abutting the anterior falx cerebri and left fovea ethmoidalis. The third case was described in 2013 by Ben Nsir et al. in a 24-year-old lady with Ewing’s sarcoma of the pelvis, lung metastases, and an extra-axial right frontoparietal mass on MRI brain mimicking a meningioma.^[7] The extra-axial dural metastases in all three cases mimicked meningioma or schwannoma. Similarly, our patient had dural metastases 2 years after Ewing’s sarcoma of the pelvis was detected. The imaging showed metastatic deposits in the right basi-occiput and right frontal region with diffuse dural enhancement in the right frontoparietal cortex suggestive of dural metastases. It can be differentiated from meningioma which typically shows diffuse, strong contrast enhancement of the entire lesion along with the adjacent margin, the dural tail sign. The lack of adjacent bony involvement, central non-enhancing hypointense lesion with enhancement of margins, along with diffuse right hemispheric dural enhancement, and an additional bony deposit at basi-occiput are clearly suggestive of dural metastases in our patient. The lack of bone involvement suggests the possibility of hematogenous spread with dural metastases in the present case.

CONCLUSION

Despite its rarity, metastatic Ewing’s sarcoma must be considered in the differential diagnosis of extra-axial dural lesions.