PMC3399549_01
Axial and coronal T1W MRI with contrast showing a left vestibular schwannoma at the time before SRT (2005).
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fig1
The tumor had been well controlled for 6 years after SRT.  Figure 1 revealed the MRI Axial and Coronal showing a left VS at the time before SRT.
(a) Axial and Coronal CT with contrast showing radiological recurrence consistent with symptomatic recurrence 6 years after SRT (2011). (b) MRI was done at 3 weeks after recraniotomy with partial tumor removal. There was residual tumor with intense enhancement at the left internal auditory canal, measured about 0.9 x 0.8 x 1.5 cm3 in size, tumor volume measured about 0.535 cc. Newly seen was the cluster of hypointense T1/heterogeneous dark-hypointense T2 lesions with hyperintense T1 rim at the superior aspect of the surgical site, involving the left-sided prepontine cistern left-sided perimesencephalic and ambient cistern measured about 2.6 x 1.6 x 2.4 cm in AP, transverse and vertical greatest dimension. These findings were suggestive of the resolving hematomas. (c) The last CT scan of the patient. During 10 fractions of 3D-CRT, the patient developed deterioration of consciousness. CT scan showed rapid progression of residual tumor with internal bleeding. Obstructive hydrocephalus was more severe.
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fig2
CPA with new obstructive hydrocephalus (Figure 2(a)). Craniotomy with tumor removal was done immediately. MRI was performed at 3 weeks after operation, and the study shows small residual tumor at the left internal auditory canal with the cluster lesions at the superior aspect of the surgical site that is compatible with the resolving hematomas (Figure 2(b)). CT emergency was done and showed progression of residual tumor with internal bleeding (Figure 2(c)).
Histopathology of the first diagnosis of schwannoma (1(a), x40), histopathology of the following specimen showing malignant peripheral nerve sheath tumor (MPNST) arising in schwannoma (1(b), x40), MPNST with chondrosarcomatous component (1(c), x40), MPNST with area composed of round cell tumor and brisk mitotic activity (1(d), x100), MPNST with pleomorphic nuclei (1(e), x400), MPNST with rhabdomyoblastic differentiation (1(f), x400), MPNST showing immunonegativity for S-100 (1(g), X400), MPNST showing sarcomeric actin immunoreactivity (1(h), x400), and MPNST with high Ki-67 immunohistochemistry (1(i), x400).
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The two pathological specimens were examined in two occasions as shown in Figure 3. The first specimen reveals low cellularity spindle cell tumor with minimal nuclear atypia and fibrillary cytoplasm that are compatible with schwannoma (Figure 3(a)).  The cytoplasm is typically light staining and indistinct (Figure 3(b)). A few areas of markedly pleomorphic nuclei, brisk mitotic activity, and round cells epithelioid appearance are also seen (Figures 3(d) and 3(e)). In this case, pluridirectional differentiations are observed as chondrosarcomatous component (Figure 3(c)) and rhabdomyoblastic component (Figure 3(f)).  Immunohistochemically, S-100 is negative (Figure 3(g)) and confirms rhabdoid/skeletal muscle differentiation with positive staining with sarcomeric actin (Figure 3(h)). The high proliferative index (Ki 67) is also seen supporting malignant behavior (Figure 3(i)).