Page 904 - Textbook of Pathology, 6th Edition

888 in 3rd to 4th decades of life. It occurs in the cerebral
hemispheres, most commonly in the frontal lobes or within
the ventricles. X-ray examination and CT scan reveal a well-
defined mass with numerous small foci of calcification. The
tumour is generally slow-growing.
MORPHOLOGIC FEATURES. Grossly, oligodendro-
glioma is well-circumscribed, grey-white and gelatinous
mass having cystic areas, foci of haemorrhages and
calcification.
Microscopically, the tumour is characterised by uniform
cells with round to oval nuclei surrounded by a clear halo
of cytoplasm and well-defined cell membranes. Tumour
cells tend to cluster around the native neurons forming
satellitosis. Typically, there are varying degree of endo-
thelial cell hyperplasia and foci of calcification. Anaplastic
change may occur as in other gliomas.

Ependymoma
Ependymoma is not an uncommon tumour, derived from
the layer of epithelium that lines the ventricles and the central
Figure 30.14 Glioblastoma multiforme (WHO grade IV astrocytoma). canal of the spinal cord. It occurs chiefly in children and
The tumour is densely cellular having marked pleomorphism.
Characteristically, the tumour has areas of necrosis which are surrounded young adults (below 20 years of age). Typically, it is
by a palisade layer of tumour cells. encountered in the fourth ventricle (posterior fossa tumour).
Other locations are the lateral ventricles, the third ventricle,
and in the case of adults, the spinal cord in the region of
Histologically, the features are as under (Fig. 30.14): lumbar spine. Clinically, by virtue of their frequent location
i) It has highly anaplastic and cellular appearance. The in the floor of the fourth ventricle, ependymomas are asso-
cell types show marked variation consisting of fusiform ciated with obstructive hydrocephalus. The usual biologic
cells, small poorly-differentiated round cells, pleomorphic behaviour is of a slow-growing tumour over a period of years.
SECTION III
cells and giant cells. Mitoses are quite frequent and glial
fibrils are scanty. MORPHOLOGIC FEATURES. Grossly, ependymoma is
ii) It shows areas of tumour necrosis around which a well-demarcated tumour but complete surgical removal
tumour cells may form pseudopalisading. may not be possible due to close proximity to vital
iii) Microvascular endothelial proliferation is marked. structures in the medulla and pons.
Microscopically, the tumour is composed of uniform
epithelial (ependymal) cells forming rosettes, canals and
Oligodendroglioma perivascular pseudorosettes. By light microscopy under
Oligodendroglioma is an uncommon glioma of oligo- high magnification, PTAH-positive structures, blepharo-
dendroglial origin and may develop in isolation or may be plasts, representing basal bodies of cilia may be
mixed with other glial cells. The tumour commonly presents demonstrated in the cytoplasm of tumour cells (Fig. 30.15).
Systemic Pathology

Figure 30.15 Ependymoma showing uniform ependymal tumour cells forming rosettes and canaliculi.