Teaching Case

Female 26 years old patient with a 5 year history of partial complex seizures

Patient with a 5 year history of partial complex seizures and decreased right eye vision since childhood. Neurologic examination demonstrated bilateral homonymous hemianopsia. Computed Tomography (CT) scan disclosed a left pasagittal mass, partially cystic and partially solid. The cystic component was localized infratentorially and the solid part was supratentorial. After contrast administration the solid part of the tumour showed homogeneous enhancement. Obstructive hydrocephalus was also noted. On Magnetic Resonance Imaging (MRI) the cystic component was hypointense on T1 weighted images and hyperintense on T2 weighted images, following the signal characteristics of CSF. The solid part was isointense with gray matter on T1 weighted images and hyperintense on T2 weighted images with marked enhancement with gadolinium. Extensive vasogenic edema was found supratentorially in the left cerebral hemisphere, surrounding the solid tumour component. At surgery a subtotal resection was achieved, part of the solid component could not be removed. At four months follow-up MRI study no progression of the residual tumour was found. Histologically the tumour was composed of fusiform cells mixed with dense cellular areas dense with large, hyperchromatic, pleomorphic, and multinucleated cells. A few cells were partly surrounded by a discontinuous external lamina that occasionally invaginated deeply into the cytoplasm and formed pseudoinclusions reminiscent of fat droplets. No necrosis or mitosis was identified.

Pleomorphic xanthoastrocytoma (PXA) is a rare, usually benign tumour. It was first described by Keppes et al. (1) in 1979. The tumour occurs primarily in children or young adults and affects males and females equal numbers. Typically, patients have a long history of seizures (2). It differs from other cerebral astrocytomas by having a favourable prognosis, although malignant conversion has been reported (3)PXA is often located in the cerebral cortex; sometimes the leptomeningeal layers are involved as well. Macroscopically and radiologically a cystic lesion with a solid component is typical. A possible preneoplastic role of cortical dysplasia has been reported in the subsequent development of PXA. It has been suggested that cortical dysplasia may predate gangliogliomas in the CNS and may play a causative role in the development of some other tumours (4) On CT and MRI images PXA is usually a cystic lesion lying superficially in the temporoparietal region and characterized by a mural nodule, which enhances markedly. On MRI images the solid tumour component is isointense to gray matter on T1 weighted images and more or less hyperintense on T2 weighted images. The solid tumour formation at the margin of a cystic formation always enhances after Gd-DTPA injection (2). These characteristics are non-specific, other tumours such as ganglioglioma and pylocitic astrocytoma may appear the same (2). Leptomeningeal enhancement and peritumoral edema have been reported. Evidence of meningeal infiltration could be a strong diagnostic argument, because meningeal infiltration is much less common in other gliomas, with exception of pilocytic astrocytoma. Peritumoral edema has been reported as a poor prognostic factor (2). Pleomorphic xanthoastrocytoma has also been confused with meningeal neoplasms such as fibrous histiocytoma or meningioma especially in cases with a unique solid component and associated meningeal enhancement (2). In our case the mass showed characteristic cystic and solid components but we could not demonstrate any meningeal enhancement. Due to the location of the mass in the midline it was difficult to define if it was intra or extra-axial. MRI in this case was useful to determine the intra-axial origin of the tumour. Histologic features include the presence of dense cellular areas with large hyperchromatic, pleomorphic cells that may be multinucleated; lipidization of astrocytes; foci of perivascular lymphocytes and abundant reticulin network, whereas necrosis is always absent (2). In conclusion PXA is a rare cortically based tumour and is usually benign. The most common clinical findings are seizures and headache. The majority of PXA's have cystic and solid areas, with strong enhancement of the solid component. Meningeal enhancement is frequently found as well.