Case Study 14
Gabrielle Yeaney, M.D.
Question 1
70-year-old man who complains of intermittent
dizziness and unsteadiness for 1 week.
Describe the MRI findings (location, enhancement,
mass effect).
MRI Sagittal T1
MRI axial FLAIR
MRI axial T1 post contrast
MRI Coronal T1 post contrast
Answer
The right posterior fossa (cerebellum) shows a wellcircumscribed homogeneously-enhancing duralbasedmass with extension through the tentorium to the
right occipital lobe. There is some mass effect in the 4th
ventricle and edema in the right cerebellar hemisphere.
Question 2
Give your differential diagnosis for this dural-based mass.
Answer
 Meningioma
 Hemangiopericytoma (HPC)
 Metastasis
 Secondary Lymphoma
 Other very rare entities: solitary fibrous tumor
(some believe SFT may be the same as HPC but
on one end of a morphologic spectrum); primary
leptomeningeal melanocytoma (bright on T1, dark
on T2); leiomyomatous and fibrohistiocytic tumors;
synovial sarcoma
Question 3
A right occipital and suboccipital craniectomy is performed
and an intraoperative consult is requested. Describe the
cytologic features of the touch prep and smear.
Click here to view slides.
Answer
There are abundant dyshesive cells with uniform ovoid
nuclei and scant cytoplasm. Nuclear outlines are smooth
but occasionally indented. Nucleoli are inconspicuous.
Mitotic figures are infrequent. There are no whorls.
Question 4
What is your intraoperative diagnosis? (A.
Neoplastic/Defer/Non-neoplastic, B. ______)
Answer
A. Neoplastic
B. Atypical; Further classification would be difficult at
this point but you could communicate a differential of
atypical meningioma, hemangiopericytoma or some
other mesenchymal neoplasm.
Question 5
Review the permanent section of the morcellated
specimen. Describe the histologic features.
Click here to view slide.
Answer
This cellular lesion is arranged in sheets with a turbulent
swirling pattern. There is little intervening stroma, but thin
strands of eosinophilic collagen can be seen between the
densely packed cells. A rare staghorn like vessel is
present (black arrow). Mitotic figures are difficult to find.
Question 6
What additional studies would you order to confirm your
diagnosis?
Answer
Reticulin!!! IHC stains that may be helpful: CD34, factor
XIIIa, bcl-2, CD99, smooth muscle markers, leu-7, EMA,
vimentin (to access immunoviablility), Ki-67
Question 7
Interpret the reticulin stain and the following
immunohistochemical stains.
Click here to view slides.
Answer
Reticulin fibers are abundant and diffuse, surrounding individual tumor cells. Tumor cells diffusely express CD34,
vimentin and CD99 but are negative for AE1/AE3. There is focal weak positivity for factor XIIIa and EMA. Ki-67
shows a tumor cell proliferation rate of 4%.
Differentiating HPC from meningioma is a recurring challenge (nightmare?) for neuropathologists. The following data
is from a study that compared 19 meningeal HPCs and 19 anaplastic meningiomas (MIIIs). IHC was performed by
using EMA, CAM 5.2, CD99, Bcl-2, claudin-1 and Factor XIIIa (FXIIIa) antibodies. FISH was performed with NF2,
4.1B (DAL-1), chromosome 1p32, and 14q32 probes. HPCs showed strong CD99 (85% of cases), strong bcl-2
(86%), focal EMA (33%), focal claudin-1 (13%), and scattered individual cell FXIIIa (100%) positivity. Anaplastic
meningiomas showed strong EMA (89%), strong claudin-1 (54%), weak or focal CD99 (15%), weak or focal bcl-2
(31%), and individual cell FXIIIa (84%) positivity. Focal CAM 5.2 expression was seen in 26% of HPCs and 15% of
MIIIs. Deletions were extremely common in MIIIs: 1p (94%), 14q (67%), NF2 (100%), and 4.1B (67%). HPCs
showed no 14q or 4.1B deletions, with 1 case each of 1p and NF2 deletions (6%). The sensitivities and
specificities of the 3 most useful IHC markers (EMA, CD99, bcl-2) were 85%-89% and 67%-84%,
respectively. Conclusions from the study were as follows: (1) EMA, CD99, bcl-2, and claudin-1 IHC and 1p, 14q,
NF2, and 4.1B FISH are particularly useful for distinguishing anaplastic meningiomas from meningeal HPCs. (2)
Focal EMA expression does not preclude a diagnosis of HPC. (3) The characteristic FXIIIa staining pattern reported
for HPC also is encountered frequently in anaplastic meningiomas and therefore is nonspecific in this diagnostic
setting. Rajaram V, Brat DJ, Perry A (2004) Anaplastic Meningioma Versus Meningeal Hemangiopericytoma:
Immunohistochemical and Genetic Markers Human Pathology 35(11)
Question 8
What is your final diagnosis?
Answer
Hemangiopericytoma—The meningeal
hemangiopericytoma was first described in 1928 by Bailey
et al., who considered the tumor an "angioblastic" variant
of meningioma. HPCs are thought to be derived from
pericytes.
Question 9
What is the prognosis, standard treatment etc?
Answer
Despite their amenability to surgical enucleation, HPCs
have a high local recurrence rate and propensity for late
metastasis. 5-, 10- and 15-year survival rates have been
quoted at 67%, 40%, and 23%, respectively. Favored
metastatic sites are bone, liver, lung, CNS. Radiotherapy
may improve survival. HPC can be subclassified into
differentiated and anaplastic based on the presence of
necrosis or brisk mitotic activity (>5/10 HPFs) and 2 or
more of the following: hemorrhage, marked cytologic
atypia, high cellularity. Ki-67/ MIB-1 indices vary from
case to case, 1%-39% in one series with little relationship
to outcome.
Question 10
What is a pericyte?
Answer
Pericytes are specialized mesenchymal cells that
are supportive to microvasculature. There is
evidence that pericytes participate in vascular
basement membrane synthesis, contraction and
phagocytosis. Pericytes have been reported to
act as oligopotential cells with the capacity to
differentiate into adipocytes, osteoblasts and
phagocytes when required. In addition, pericytes
are considered to play a role in angiogenesis and
antigen presentation.