Ewing sarcoma - C1
Right sub-occipital mass.
CT cervical spine
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A large soft tissue mass measuring three .8th by 5.3 x 4 .4 cm is located on the right side of the neck, the epicenter centred on the transverse process of the C1 vertebra which it destroys. Further patchy destructive bony changes demonstrated within the lateral mass of C1 on the right - it has an aggressive permeative appearance - and is associated with a pathological fracture which extends through the foramen transversarium. The right vertebral artery is displaced medially by the mass, which involves the foramen transverse variant, and appears extrinsic be compressed but not occluded. There is no evidence of epidural extension.
The mass is somewhat heterogeneous, but appears of mostly solid, with no matrix calcification, no periosteal reaction, no convincing cystic component. Although the mass does abut the base of skull superiorly and the transverse process of C2 inferiorly, there are no destructive bony changes at either site.
A number of lymph nodes are slightly prominent, but these are symmetric, and in a patient of this age within normal limits. The remainder of the scan is unremarkable, with no other bony lesions identified. The apices of the lungs appear normal. The portions of the brain which have been imaged (up to the level of the foramen of Monro) appear unremarkable.
4 case question available
MRI spine / base of skull
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Pre-and post-contrast study of the head and neck including MRA is compared with CT dated same day.
A large isointense T1, hyperintense T2 and enhancing mass is centred on the right transverse process of C1. It demonstrates relatively elevated restricted diffusion. The lesion is predominantly soft tissue in location but does invade the transverse process, lateral mass and anterior and posterior arches of C1 on the right. High suspicion of extension into the lateral aspect of the right occipital condyle and adjacent occipital squama, tumour abutting without invading through the hypoglossal canal. The mass largely displaces the posterior deep cervical musculature and extends beneath the right longus capitis, separating the lateral portion from the vertebral column. Mass also abuts without overtly encasing a long segment of the right vertebral artery, causing irregularity and some compression, particularly at the C0/C1 level. The right internal jugular vein is also compressed. Although tumour abuts the thecal sac at the right lateral aspect of the C1/2 interspace, there is no discrete epidural extension and no intracranial extension.
Symmetrical cervical lymph nodes are of normal size for age. The intracranial structures and the remainder of the MRA is unremarkable, in particular, no evidence of metastasis or posterior circulation ischaemia.
This patient went on to have a biopsy.
Sections show multiple cores of ?brous tissue with a small amount of fat, skeletal muscle and lamellar bone. There is in?ltration by a highly cellular and viable tumour comprising sheets of small round cells. The tumour cells have ovoid nuclei, inconspicuous nucleoli and scant cytoplasm. The periodic acid-Schiff stain shows copious amounts of cytoplasmic glycogen. ImmunoMstochemical studies have been performed and the tumour cells show membranous staining for CD99. The tumour cells are negative for desmin, myogenin, CD45, TdT and chromogranin. The normal nuclear staining for INI-1 is retained.
The features are consistent with Ewing's sarcoma.
A vertebral mass in an otherwise well child which has no matrix mineralisation / ossification has a relatively limited differential including:
- eosinophilic granuloma
- aneurysmal bone cyst: fluid fluid levels would be typical
- giant cell tumour
- Ewing sarcoma
Given the clearly aggressive interface with bone, which is destroyed, a malignancy was unfortunately the most likely diagnosis in this case, and Ewing's sarcoma the most likely entity.