Contributed by Julia Pöschl1, Frank Berger2, Hans Kretzschmar1 and Ulrich Schüller1
1Center for Neuropathology and Prion Research, Ludwig-Maximilians-University, Munich, Germany;
2Department of Clinical Radiology, University of Munich, Munich, Germany
CLINICAL HISTORY AND IMAGING
A 59-year old man presented with metastasizing adenocarcinoma of the lung. Within the scope of staging analysis, brain imaging was performed and showed an enlarged posterior fossa with separated cerebellar hemispheres. The cerebellar vermis was absent and instead, a tumor was attached to the meninges at the occipital part of the posterior fossa (Figure 1, Axial T2 weighted cranial MRI). The patient received radiochemotherapy, but finally died of respiratory insufficiency with diffuse alveolar damage.
MACROSCOPIC AND MICROSCOPIC PATHOLOGY
Autopsy revealed a grossly abnormal cerebellum with absent vermis (Figure 2). The nucleus dentatus did not have the normal angular shape, but lined the fourth ventricle. The dorsal tumor was 4.5 x 3 x 1.5 cm in size and was attached to the dura mater and cystic ventricular walls (Figure 3). The tumor cross section showed white, beige and yellowish areas with indistinct borders (Figure 3). Histologically, the tumor had a heterogeneous appearance and contained mature tissues (Figures 4, 5 and 6). Cytokeratin strongly stained some cells (Figure 7) and GFAP was positive in other areas of the tumor (Figure 8). One area contained pigmented cells (Figure 9). No mitoses or necrosis was present.
Unexpectedly, another smaller lesion was found in the right cerebellar hemisphere that was gray-white with a well-defined margin (Figure 10, arrow). This lesion was not apparent on the MRI performed 6 months before death. Histology showed a malignant tumor with necrosis (Figure 11) that also stained for keratin (Figure 12).
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