Contributed by Julia Kofler, MD and Geoffrey Murdoch, MD, PhD
Published on line in July 2006
The patient is a 57-year old female with a past medical history of thyroidectomy, hysterectomy, and papillary fibroepithelial hyperplasia of the buccal mucosa. She presented with a three-month history of progressive vertigo, ataxia, and posterior headache. Physical examination revealed lateral nystagmus, dysdiadochokinesis and ataxia.
CT scan demonstrated a left cerebellar mass with coarse calcifications and mass effect on the fourth ventricle, with dilatation of the third and lateral ventricles. MRI showed a large, minimally contrast-enhancing mass with a striated appearance on T2-weighted images (figure 1, T2; figure 2, T1 with contrast).
The patient underwent left suboccipital craniotomy with partial mass resection and placement of a ventricular drain.
The specimen consisted of two fragments. One fragment (5.0 x 2.5 x 1.5 cm) had normal appearing longitudinal, 2 mm wide folia (figure 3, left). The second fragment (5.5 x 2.0 x 2.0 cm) exhibited expanded folia, up to 6 mm wide (figure 3, right, bisected).
Microscopic examination of the second fragment revealed marked changes of the cerebellar architecture with expansion of the folia (figures 4 and 5). The granular and Purkinje cell layers were replaced by an inner layer of large neuron-like polygonal cells with prominent nucleoli (figures 6, 7, 8, and 9). The molecular layer had increased cellularity and an abnormal outer layer of myelinated axon bundles (figure 20, Luxol fast blue). In addition, there were prominent microcalcifications, increased vascularity and vacuolization of the molecular layer (figure 10). The normal deep layer of myelinated fibers was virtually absent (figure 20, Luxol fast blue).
Sections of the grossly normal appearing first fragment revealed transitional changes from normal cerebellar architecture (figures 11, 12 and 13; figure 18, Luxol fast blue) to fully developed lesion. The transitional zone showed a gradual increase in the number of large polygonal cells in the granular cell layer with concomitant decrease in granular neurons (figures 14, 15, 16 and 17). As best seen with Luxol fast blue stain, these cellular changes were accompanied by a gradual increase in myelinated fibers in the molecular layer, and decrease in central white matter (figure 19).
Ki-67 immunostain was negative in the dysplastic ganglion cells, indicating no proliferative activity.