Neurol Med Chir (Tokyo) 51, 79¿81, 2011

Inflammatory Myofibroblastic Tumor
of the Cerebellar Hemisphere
—Case Report—
Koichi KATO,1 Yosuke MOTEKI,1 Masanori NAKAGAWA,1
Shigeru KADOYAMA,1 and Hiroshi UJIIE1
1Department of Neurosurgery, Tokyo Rosai Hospital, Tokyo

Abstract
A 60-year-old man presented with a rare cerebellar inflammatory myofibroblastic tumor (IMT) manifesting as gait disturbance and dysarthria. Brain magnetic resonance imaging demonstrated an intra-axial
round-shaped isointense mass homogeneously enhanced with gadolinium in the right cerebellar
hemisphere, as well as perifocal edema extending to the brain stem and right thalamus. The tumor was
elastic hard and was resected en bloc with a clear margin. Histological examination revealed IMT with
spindle cells and collagen, but negative for anaplastic lymphoma kinase expression. IMT most commonly affects the lung, but may involve many other parts of the body. There is some debate regarding
the disease entity of IMT in the central nervous system (IMT-CNS) because of its rarity and high frequency of recurrence. IMT-CNS is an important differential diagnosis among tumor-like intracranial
lesions and total resection is required.
Key words: brain edema, central nervous system, cerebellar tumor,
inflammatory myofibroblastic tumor, inflammatory pseudotumor

Introduction

Case Report

Inflammatory myofibroblastic tumor (IMT), or inflammatory pseudotumor, is a rare lesion consisting of myofibroblastic spindle cells and inflammatory cells that occurs
primarily in soft tissue and the viscera of children and
young adults.3,5) IMT can affect any part of the body, but is
most commonly seen in the lung, mesentery, and omentum, and usually follows a benign clinical course. Diagnosis depends on histological examination because the radiological and clinical findings are non-specific. IMT has
been described under many different names, such as inflammatory pseudotumor and plasma cell granuloma, suggesting the complexity and variable histological characteristics of the tumor.8) The etiology of IMT remains
unknown, and both neoplastic and non-neoplastic
processes have been proposed.11) IMT in the central nervous system (IMT-CNS) is rare, and tends to arise from
meningeal structures and recur. The disease entity of
IMT-CNS has become contentious recently because of the
high frequency of recurrence and malignant transformation compared with IMT not affecting the CNS (IMTnCNS).6,10,11)
Here we describe a case of cerebellar intraparenchymatous IMT in an adult, which seemed to exhibit the benign
and inflammatory characteristics of IMT-CNS or inflammatory pseudotumor.

A 60-year-old man was admitted to our hospital complaining of rapidly progressing gait disturbance and ataxia.
Neurological examination revealed right abducens palsy,
right facial palsy (House-Brackmann grade III), dysarthria,
and cerebellar ataxia. There was no past history except for
diabetes mellitus. General physical examination was within normal limits. Results of blood examination were normal, including tumor markers (squamous cell carcinoma
antigen, carcinoembryonic antigen, a-fetoprotein, carbohydrate antigen 19–9, and prostate-specific antigen), bmicroglobulin, and interleukin-2 receptor. Computed
tomography showed a homogeneously enhanced, roundshaped intra-axial mass in the right cerebellar hemisphere
compressing the brain stem. Brain magnetic resonance
imaging demonstrated an isointense mass enhanced by
gadolinium, with perifocal edema extending to the brain
stem and right thalamus (Fig. 1). Cerebral angiography
showed no abnormalities and whole-body gallium scintigraphy was negative.
Intraoperatively, a yellowish, well-demarcated tumor
was identified using a navigation system (Fig. 2A). The
tumor was elastic hard and fibrous, and approximately 18
mm in size. The lesion was resected en bloc (Fig. 2B).
Histological examination revealed spindle cells, collagen,
and central necrosis (Fig. 3A). Immunostaining demonstrated that the spindle cells reacted with smooth muscle
actin and vimentin (Fig. 3B, C). The histological diagnosis

Received

March 3, 2010;

Accepted

May 27, 2010

79

K. Kato et al.

80

Fig. 3 A: Photomicrograph of the tumor showing spindle
cells, collagen, and central necrotic zones. Hematoxylin and
eosin stain, original magnification ×40. B, C: Immunohistochemical examination showing the spindle cells are positive for smooth muscle actin (B) and vimentin (C). ×40.

Fig. 1 A: Axial T1-weighted magnetic resonance (MR) image
demonstrating a round-shaped isointense mass in the right
cerebellar hemisphere. B: Axial T1-weighted MR image after
administration of gadolinium showing the mass is well demarcated and homogeneously enhanced. C, D: T2-weighted MR
images showing the isointense mass with perifocal edema extending to the brain stem and the right thalamus.

Fig. 2 Intraoperative photographs showing a yellowish, welldemarcated tumor in the cerebellar parenchyma (A), and the
resected mass is smooth and firm, and uniform throughout (B).

was IMT (inflammatory pseudotumor). No mitoses were
detected, and the MIB-1 index was lower than 1%.
Anaplastic lymphoma kinase (ALK) expression was negative. The postoperative course was uneventful and no
recurrence was observed during the 8-month follow-up
period.

Discussion
IMT is a distinctive myofibroblastic spindle cell lesion accompanied by an inflammatory infiltrate of plasma cells,

lymphocytes, and eosinophils.4) IMT-CNS is rare, with
only approximately 70 reported cases.6,10) In the present
case, positive immunohistochemical results for smooth
muscle actin and vimentin agreed with previous reports of
IMT.3,5,11) Localization of IMT can be divided into 5 types:
intraparenchymatous, meningeal, mixed intraparenchymatous and meningeal, intraventricular, and extending to the cranial cavity/sphenoid sinus.6) The etiology of
IMT-CNS is unknown, but 60% (34/57) of IMT-CNS
tumors have arisen from the dural/meningeal structures
and only 12% (7/57) from intraparenchymatous lesions.6)
The present case had no attachment to dural/meningeal
structures, and was classified as the intraparenchymatous
type.
The neuroimaging findings and clinical course of IMTCNS are non-specific, such that differential diagnosis is
important in the case of meningeal lesions, especially with
meningioma or sarcoma.1,2,9,12) Earlier cases likely included an indiscriminate mixture of neoplastic and nonneoplastic process. Of patients with extrapulmonary IMT,
15% (13/84) had one or more recurrences over a period of
1–24 months (mean 6 months),3) but patients with IMTCNS had recurrence rate after incomplete resection of
40% within 2 years.6) Two of the three young patients with
IMT-CNS extending from the meningeal structures into
the brain tissue showed local recurrence after resection of
the tumor and histological investigations revealed transformation into a semimalignant fibrohistiocytic tumor in
one patient.6) Therefore, whether IMT-CNS is a different
entity from IMT-nCNS remains controversial.6,10,11) The
potential risk of malignant transformation and high risk of
recurrence necessitate close follow up, particularly if
resection was incomplete.7)
Staining of ALK on chromosome 2p23, which is well
known from anaplastic large cell lymphomas, can be detected in approximately 50% of cases of IMT-nCNS and

Neurol Med Chir (Tokyo) 51, January, 2011

Cerebellar IMT
correlates with the rearrangement of ALK.4,6,9,11) This suggests that some of IMTs with ALK activation could be of
neoplastic origin.10) Three of four cases of IMT-CNS
showed ALK protein overexpression immnohistochemistry.11) The present case was negative for ALK, and MIB-1
index was lower than 1%. However, necrosis was detected
microscopically. Necrosis was detected in 6 of the 60 cases
of IMT-CNS,6) and atypical forms may undergo malignant
transformation.
Orbital pseudotumor extending into the cranial cavity is
a well-described, distinct entity and does not require total
resection. In contrast, there is some debate regarding the
nature of IMT-CNS, such as whether this is a homogeneous entity, whether the tumor is neoplastic, and if neoplastic, the level of malignancy. No specific treatment protocol
has not been developed for IMT-CNS because of its rarity,
but total resection and close follow up seem essential because of the variable prognosis.

References
1)

Bramwit M, Kalina P, Rustia-Villa M: Inflammatory pseudotumor of the choroid plexus. AJNR Am J Neuroradiol 18:
1307–1309, 1997
2) Brandsma D, Jansen GH, Spliet W, Van Nielen K, Taphoorn
MJ: The diagnostic difficulties of meningeal and intracerebral plasma cell granulomas-presentation of three
cases. J Neurol 250: 1302–1306, 2003
3) Coffin CM, Watterson J, Priest JR, Dehner LP: Extrapulmonary inflammatory myofibroblastic tumor (inflammatory
pseudotumor). A clinicopathologic and immunohistochemical study of 84 cases. Am J Surg Pathol 19: 859–872, 1995
4) Cook JR, Dehner LP, Collins MH, Ma Z, Morris SW, Coffin
CM, Hill DA: Anaplastic lymphoma kinase (ALK) expression
in the inflammatory myofibroblastic tumor: a comparative
immunohistochemical study. Am J Surg Pathol 25: 1364–

Neurol Med Chir (Tokyo) 51, January, 2011

81

1371, 2001
Fletcher CDM, Unni KK, Mertens F: Wold Health Organization Classification of Tumours, Pathology & Genetics of
Tumours of Soft Tissue and Bone. Lyon, IACR Press, 2002,
pp 91–93
6) H äausler M, Schaade L, Ramaekers VT, Doenges M, Heimann G, Sellhaus B: Inflammatory pseudotumors of the central nervous system: report of 3 cases and a literature review.
Hum Pathol 34: 253–262, 2003
7) Jeon YK, Chang KH, Suh YL, Jung HW, Park SH: Inflammatory myofibroblastic tumor of the central nervous system:
clinicopathologic analysis of 10 cases. J Neuropathol Exp
Neurol 64: 254–259, 2005
8) Narla LD, Newman B, Spottswood SS, Narla S, Kolli R: Inflammatory pseudotumor. Radiographics 23: 719–723, 2003
9) Qiu X, Montgomery E, Sun B: Inflammatory myofibroblastic
tumor and low-grade myofibroblastic sarcoma: a comparative study of clinicopathologic features and further observations on the immunohistochemical profile of myofibroblasts.
Hum Pathol 39: 846–856, 2008
10) Suri V, Shukla B, Garg A, Singh M, Rishi A, Sharma MC,
Sarkar C: Intracranial inflammatory pseudotumor: Report of
a rare case. Neuropathology 28: 444–447, 2008
11) Swain RS, Tihan T, Horvai AE, Vizio DD, Loda M, Burger
PC, Scheithauer BW, Kim GE: Inflammatory myofibroblastic tumor of the central nervous system and its relationship
to inflammatory pseudotumor. Hum Pathol 39: 410–419,
2008
12) Yamaki T, Ikeda T, Sakamoto Y, Ohtaki M, Hashi K: Lymphoplasmacyte-rich meningioma with clinical resemblance
to inflammatory pseudotumor. J Neurosurg 86: 894–904,
1997
5)

Address reprint requests to: Koichi Kato, MD, Department of Neurosurgery, Tokyo Rosai Hospital, 4–13–21 Omori-minami,
Ota–ku, Tokyo 143–0013, Japan.
e-mail: kkato＠tokyoh.rofuku.go.jp