Department of Pathology,
University of Oklahoma Health Sciences Center
NeuroTest Question #14
Answer: D (Pleomorphic
Level of difficulty: 3
Lesion under discussion: The lesional tissue is
composed of neoplastic cells with substantial pleomorphism. The salient
diagnostic clue is the large cell with foamy cytoplasm located at the upper
part of the field; a typical feature in pleomorphic xanthoastrocytoma (PXA).
- Dyembryoplastic neuroepithelial tumor (DNET): The
histology can be quite variable but the large cells and cytologic atypia
being shown here is not a feature of DNET.
- Large cell medulloblastoma: Large cell
medulloblastoma essentially maintains the appearance of medulloblastoma but
with large nuclei and increased pleomorphism. The large nucleus in large
cell medulloblastoma often "hug" on a smaller nucleus. The tumor
being illustrated here has no resemblance to medulloblastoma.
- Pleomorphic xanthoastrochtoma (PXA): This is an
uncommon tumor that accounts for less than 1% of all astrocytic tumors; most
of them are seen in children and young adults. Although they have favorable
prognosis, about one-fifth of the cases may have malignant transformation.
They tend to occur in supratentorial locations as superficial tumors with
leptomenigeal involvement. Histologically,
is a variegated appearance of the tumor with spindly elements intermingled
with mono- or multinucleated giant cellls, the nuclei of which display great
variation in size and staining. Mitotic activity is not very conspicuous, if
present. Necrosis is not seen. As being illustrated here, there is intracellular
accumulation of lipid droplets that often occupy much of the cell body; the
nuclei and the more basophilic cytoplasm are often pushed to the side. As a
result, immunostaining often demonstrate crescents of cytoplasm that are
immunoreactive for GFAP. Reticulin fibers can be well demonstrated in the
tumor and in leptomeninges being invaded by tumor cells.