Case Study 13
Gabrielle Yeaney, M.D.
Question 1
40-year-old female with headache and word-finding
problems, no other past medical history.
Describe the MRI findings (location, enhancement,
mass effect).
Sagittal T1
Axial T2 FLAIR
Coronal T1 post contrast
Answer
There is a heterogenous cystic mass within the right lateral
ventricle (4.4 x 2.5 x 2.5 cm). The mass demonstrates
minimal to no enhancement. There is mild enlargement of
the right lateral ventricle, including the temporal horn. The
mass is associated with the septum pellucidum. There is
mild leftward deviation of the septum.
Question 2
What is your differential diagnosis based on MRI?
Answer
 Ependymoma
 Subependymoma
 Central neurocytoma
 Choroid plexus tumors (lateral and third--children;
fourth--adults)
 Pilocytic astrocytoma
 Subependymal giant cell astrocytoma (h/o tuberous
sclerosis)
 Meningioma (rare)
Question 3
A craniotomy is performed and you do a smear prep for
intraoperative diagnosis. Describe the cytologic features
of the smear.
Click here to view slide.
Answer
This hypercellular smear prep consists of a
monomorphic population of cells with small-tomedium-sized round nuclei, finely granular
chromatin and scant cytoplasm. Cells are
process-poor and are present individually, not in
clusters. A faint light pink matrix is noticeable in
the background. There is no myxoid material,
unlike oligodendroglioma. Nucleoli and mitotic
figures are not readily found. Vessels are thin
(one-cell-layer) for the most part.
Question 4
What is your intraoperative diagnosis (A.
Neoplastic/Defer/Non-neoplastic, B. ______)
Answer
A. Neoplastic
B. Low grade neoplasm with round nuclei; favor central
neurocytoma
Question 5
Review the permanent section. Describe the histologic
features.
Click here to view slide.
Answer
Histologic sections show tumor cells in sheets
with occasional paucicellular islands of
neuropil. There are scattered fine capillaries
within the tumor. Cytology is similar to that seen
on the smear (round cells, "salt-and-pepper"
chromatin), except that well defined cell borders
and perinuclear halos are seen on paraffin
sections. Rare cells show a slight increase in
cytoplasm and a small nucleolus suggestive of
neuronal differentiation. Mitotic figures are not
appreciated. There is no necrosis.
Question 6
What is your differential diagnosis (at least 2) after
reviewing the H&E sections?
Answer
Central neurocytoma vs oligodendroglioma. (Most
supratentorial ependymomas are not intraventricular but
maybe you could include clear cell
ependymoma. However, there are no perivascular
pseudorosettes on the H&E section.)
Question 7
What confirmatory immunohistochemical or other ancillary
studies would you get?
Answer
The most important stain to order would be
synaptophysin. Other helpful studies include IHC for
GFAP, Ki-67 and FISH for 1p/19q deletion. The histologic
features of neurocytoma and oligodendroglioma can be
quite similar. Neurocytoma is typically well defined on
imaging and lacks diffuse tissue infiltration, a feature that
leads to trapped neurons in oligodendroglioma. IHC for
synaptophysin is usually negative in oligodendroglioma
and positive in neurocytoma. But even the rare
oligodendroglioma may have synaptophysin-positive
rosettes. In that case, FISH studies showing lack of
1p/19q co-deletion should confirm the diagnosis of
neurocytoma. GFAP would be positive in other glial
neoplasms such as ependymoma.
Question 8
How would you describe the results of the following
immunohistochemical studies? Given these results, what
is your final diagnosis?
Click here to view slides.
Answer
Tumor cells diffusely express synaptophysin. Glial
fibrillary acidic protein (GFAP) highlights some reactive
astrocytes but the tumor cells do not express GFAP. A
few tumor cells show weak to strong expression for
neuronal marker NeuN. Ki-67 shows a tumor cell
proliferation index of 2-3% overall. Final diagnosis:
Central neurocytoma.
Question 9
What is the WHO grade?
Answer
Central neurocytoma is a WHO grade II lesion.
Question 10
Though mitotic figures are typically rare to absent in this
lesion, a range of mitotic activity, microvascular
proliferation and even necrosis is possible. Generally,
increased proliferation index (Ki-67/MIB-1 labeling) is
used to predict more aggressive behavior. What is the
threshold for "grading" this tumor based on Ki-67/MIB-1
labeling?
Answer
A threshold of 2% has been found to predict greater likelihood of
recurrence. From Mackenzie IR (1999) Central neurocytoma: histologic
atypia, proliferation potential, and clinical outcome. Cancer. 85:160610: Although central neurocytomas are considered benigh, recent reports
suggest that some patients with histologic atypia and/or elevated proliferation
potential may have a poor outcome. A retrospective review identified 15
cases of central neurocytoma.
Histologic atypia was identified in 3 tumors (20%). The MIB-1 LI ranged from
0.1% to 6.0%, and 5 cases (33%) had a MIB-1 LI > 2%. The proliferation
potential of central neurocytoma is a useful predictor of clinical outcome,
whereas histologic atypia alone is not prognostically significant. It would be
appropriate to recognize a subgroup of central neurocytomas with elevated
proliferation potential as WHO Grade 2 lesions. The terms "atypical" and
"anaplastic" are not appropriate to describe these lesions, as they imply a
certain histologic appearance. The most accurate designation would be
"proliferating neurocytoma."
Question 11
Neurocytomas can occur outside of the ventricular
system.
True or False?
Answer
True.
Darn those pesky neurocytomas can occur in many
locations. So called extraventricular, or intraparenchymal,
neurocytomas have been reported in the cerebral
hemispheres, thalamus, amygdala, pineal gland, retina,
skull base, cerebellum, pons, spinal cord and cauda
equina.