PMC3356992_01
(a) Sagittal T1-W MRI without contrast injection, before the first surgery. An extradural hyposignal lesion is observed at S1-S3 level, which was neglected in the first intervention. (b) Sagittal T1 MRI with contrast from the lumbosacral region after the first operation. Homogenous enhancement of the lesion is observed. (c and d) Axial T1 MRI views of the lesion with and without contrast, after the first operation
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F1
Scalloping of the posterior aspect of the S2 vertebra was also detectable [Figure 1a-d].
(a and b) Hematoxylin and Eosin staining of the tumor under low- and high-power microscopic fields revealing a highly cellular neoplasm composed of diffuse sheets of tumor cells having monomorphic, round to oval, finely vesicular nuclei and occasional nucleoli with indistinct cytoplasmic border. In some foci, tumor cells are grouped around small vessels (pseudo-rosette appearance). Several groups of mitotic figures were noted, but no necrosis was detected. (c) Immunohistochemistry study for CD99 depicting tumor cells highly positive for the marker
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F2
Several groups of mitotic figures were noted, but no necrosis was detected [Figure 2a and b]. Tumor cells also expressed CD99, consistent with the diagnosis of ES/PNET [Figure 2c].