The right posterior fossa (cerebellum) shows a well-
circumscribed homogeneously-enhancing dural-basedmass
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.
Give your differential diagnosis for this dural-based mass.
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;
A right occipital and suboccipital craniectomy is performed
and an intraoperative consult is requested. Describe the
cytologic features of the touch prep and smear.
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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.
What is your intraoperative diagnosis? (A.
Neoplastic/Defer/Non-neoplastic, B. ______)
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.
Review the permanent section of the morcellated specimen.
Describe the histologic features.
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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.
What additional studies would you order to confirm your
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
Interpret the reticulin stain and the following
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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
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
What is the prognosis, standard treatment etc?
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
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