Download Case Study 15 - University of Pittsburgh

Case Study 15
Gabrielle Yeaney, M.D.
Question 1
25-year-old man with history of seizures.
Describe the MRI findings (location, enhancement,
mass effect).
Axial T1
FLAIR
Axial T1 post contrast
Coronal T1 post contrast
Answer
There is a well-defined, intra-axial, partially-cystic, NONenhancing mass (2.6cm) in the left inferior temporal lobe.
There is no mass effect or midline shift.
Question 2
What is in your differential diagnosis based on MRI/ age?
Answer
Ganglioglioma, Pleomorphic xanthoastrocytoma,
Dysembryoplastic neuroepithelial tumor,
Oligodendroglioma, Extraventricular neurocytoma.
Question 3
Describe the cytologic features of the smear.
Click here to view slide.
Answer
The tissue is more cellular than normal cortex. There are
cells with round to ovoid nuclei and fibrillary processes
with admixed larger cells with round nuclei and prominent
nucleoli (neurons). Several calcifications are
present. Mitotic figures and anaplasia are not seen.
Question 4
What is your intraoperative diagnosis (A. Neoplastic /
Defer / Non-neoplastic, B. ______)?
Answer
A. Neoplastic
B. Low-grade neuroglial neoplasm; If you hadn’t seen
the imaging prior to looking at the smear, you might
defer and consider cortical dysplasia in your
differential.
Question 5
Review the permanent section and describe the histologic
features.
Click here to view slide.
Answer
The tumor shows numerous dysmorphic neurons
(ganglion cells) mixed with atypical astrocytes (enlarged
elongated nuclei with irregular nuclear contours). Mitotic
figures are not seen. There are foci of dystrophic
calcification of neurons and vessels.
Question 6
You order some immunostains to further classify the
tumor cells and look for proliferative activity. Review the
immunohistochemical studies.
Click here to view slides.
Answer
NeuN and synaptophysin highlight the neuronal
component of the tumor. Vimentin and GFAP
(overstained) highlight astrocytic processes of the tumor
cells. The proliferative activity of the tumor cells is very
low (Ki-67 = 1-2%).
Question 7
What is your final diagnosis?
Answer
Ganglioglioma
Question 8
What is the most important histologic feature that
distinguishes pilocytic astrocytoma with trapped neurons
from ganglioglioma?
Answer
The cortical neurons overrun by an infiltrating glioma
(oligo or astro) will appear cytologically normal, in contrast
to neuronal cells in a ganglioglioma which should be
dysmorphic. Dysmorphic neurons may have ganglioid
cytology, more than one nucleus, cytoplasmic vacuolation,
abnormally clumped Nissl and/or abnormal
processes. These abnormal neurons usually stain with
synaptophysin (surface positivity), chromogranin
(cytoplasmic positivity), NeuN (nuclear and cytoplasmic),
CD34. These stains are not specific, so assessment of
the morphology of the stained cell is important. Coexpression of synaptophysin and GFAP is not uncommon
and is a sign of an abnormal neuron. Crysl violet may be
helpful in highlighting cells with Nissl substance.