AJR 2005; 184:1310-1312
© American Roentgen Ray Society
Infantile Myofibromatosis of the Posterior Fossa
Phillip R. Chapman1,
Corey D. Judd1,
Judy L. Felgenhauer2,
David P. Gruber3 and
Dan Mornin4
1 Inland Imaging, 525 S Cowley St., Spokane, WA 99202.
2 Sacred Heart Children's Hospital, 101 W Eighth Ave., Spokane, WA 99204.
3 Inland Neurosurgery and Spine Associates, 105 W Eighth Ave., Ste. 200,
Spokane, WA 99204.
4 InCyte Pathology, 101 W Eighth Ave., PO Box 2555, Spokane, WA 99204.
Received May 25, 2004;
accepted after revision July 21, 2004.
Please address correspondence to P. R. Chapman
(prchapman{at}inland-imaging.com).
Introduction
Infantile myofibromatosis is considered the most common fibrous
tumor of infancy and early childhood
[1]. This disease typically
presents as multiple mesenchymal tumors arising in skin, muscle, bone,
subcutaneous tissue, and viscera. It is rare for these fibrous lesions to
involve the intracranial compartment. When this does occur, the intracranial
lesion is usually an extension of a primary process within the suprahyoid
neck, either by direct destruction of the bony skull or by transgression of
skull base foramina
[2-7].
We report a unique case of infantile myofibromatosis with intracranial
involvement. This case shows a complex lesion at the epicenter within the
posterior fossa, displacing the cerebellum, eroding the occipital bone, and
extending intravascularly through the jugular foramen into the internal
jugular vein.
Case Report
A 2-month-old male infant delivered at term was initially evaluated for a
subcutaneous mass involving the anterior right chest wall. On initial physical
examination, no other obvious lesions were identified. Biopsy of the 2-cm
chest wall mass showed histologic findings consistent with infantile
myofibromatosis. Of interest, the patient's cousin had previously been
diagnosed with infantile myofibromatosis.
Approximately 1 week after the biopsy, the patient presented with an upper
respiratory infection and developed severe stridor and respiratory distress.
Initial lateral soft-tissue neck radiographs showed a normal epiglottis and
markedly thickened aryepiglottic folds. Direct laryngoscopy confirmed the
presence of acute aryepiglottitis and laryngitis and also revealed unsuspected
left vocal cord paralysis. CT and MRI studies were then performed with the
patient under general anesthesia to evaluate the soft tissues of the neck and
skull base.
Unenhanced and contrast-enhanced CT images of the brain and neck revealed a
complex extraaxial mass within the posterior fossa on the left, measuring 5 cm
in greatest dimension. Significant mass effect with displacement of the
cerebellum and distortion of the fourth ventricle was noted. There was at
least partial obstruction of the inferior fourth ventricle, and there was mild
enlargement of the third and lateral ventricles. Subtle calcification along
the medial margin of the mass and focal nodular and curvilinear calcification
within the proximal left internal jugular vein were seen.
After contrast administration, there was thick peripheral enhancement of
the mass and enhancement of several internal septations
(Fig. 1A). The mass arose from
the lateral dural margin, directly invaded the left transverse and sigmoid
sinuses, and eroded the left occipital bone. One of the most striking features
was extension of the tumor into the jugular foramen and into the upper carotid
sheath, accounting for left vocal cord paralysis
(Fig. 1B). More specifically,
the tumor was growing intravascularly into the jugular bulb and proximal
internal jugular vein. Coronal reformatted images best showed this downward
extension, creating a stalactite-like appearance of the tumor thrombus
(Fig. 1C). Otherwise, the CT
images depicted supraglottic edema and bilateral otomastoiditis, but no other
masses in the neck.
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Fig. 1B. —2-month-old male infant with intracranial infantile
myofibromatosis. Contrast-enhanced axial CT image shows hypodense mass within
left internal jugular vein with surrounding intravascular contrast material
(arrowhead). Note presence of intratumoral calcifications.
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Fig. 1C. —2-month-old male infant with intracranial infantile
myofibromatosis. Coronal reconstructed image from contrast-enhanced CT clearly
shows stalactite-like extension of tumor into left internal jugular vein
(arrowheads).
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MRI of the brain and soft tissues of the neck was performed and again
depicted the complex extraaxial posterior fossa mass with internal jugular
vein extension. T2-weighted images showed mottled increased signal centrally
with a thin peripheral band of hypointensity. T1-weighted images showed slight
increased signal throughout much of the lesion, suggesting necrosis and
proteinaceous debris (Figs. 1D
and 1E). The MR images
confirmed the obliteration of the sigmoid sinus and enlargement of the jugular
foramen. There was also erosion of the lateral wall of the hypoglossal canal.
In addition, axial images through the lower neck and upper chest revealed
unsuspected fibromas within the right supraspinatus muscle and the right
paraspinous musculature of the upper back.
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Fig. 1D. —2-month-old male infant with intracranial infantile
myofibromatosis. On this axial T1-weighted image obtained after gadolinium
administration, tumor shows enhancement of periphery and internal septations.
Mass can be seen to extend into left jugular foramen (arrowhead).
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Fig. 1E. —2-month-old male infant with intracranial infantile
myofibromatosis. Axial T2-weighted image, obtained through same level as
D, shows heterogeneous signal throughout mass with thin, peripheral,
hypointense band.
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At surgery, the large bright yellow mass was found to be largely necrotic
with occasional areas of focal calcification. The mass completely obliterated
the sigmoid sinus and directly penetrated the lateral aspect of the occipital
bone, invading the deep scalp musculature. Direct growth into the jugular bulb
was confirmed, and the mass showed significant propensity to hemorrhage during
the subtotal resection. Care was taken to avoid damage to the lower cranial
nerves, and resection was not extended into the carotid sheath or internal
jugular vein because, typically, in cases of subtotal resection of myofibroma,
residual tumor tissue will regress spontaneously
[1]. Closure was accomplished
by use of a regionalized occipitalis muscle flap to close the large bony
defect. Pathologic evaluation confirmed the diagnosis of infantile
myofibromatosis (Fig. 1F).
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Fig. 1F. —2-month-old male infant with intracranial infantile
myofibromatosis. Photomicrograph of intracranial specimen reveals fascicles of
myofibroblasts typical of infantile myofibromatosis. (x600)
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Follow-up imaging at 1 month after resection revealed moderate reduction in
size of the residual intravascular tumor, consistent with the known natural
history of infantile myofibromatosis.
Discussion
First described by Stout in 1954
[1], infantile myofibromatosis,
one of the myofibroblastic lesions of infancy and childhood, is classically
limited to skin, soft tissues, and bone. Three classes of disease are
recognized and carry prognostic implications: solitary myofibromatosis,
congenital multiple myofibromatosis associated with multicentric lesions
without visceral involvement, and congenital generalized myofibromatosis with
both cutaneous and visceral involvement
[8]. A limited course with
spontaneous regression is typically seen when visceral organs are not
involved. However, with visceral involvement (25% of patients) the prognosis
worsens precipitously, carrying a mortality rate of 76%
[8]. Death occurs during the
first few days or weeks of life before the complicating lesions have the
opportunity to regress.
The exact incidence of infantile myofibromatosis is unknown. Most reports
suggest that the incidence is underdiagnosed, both because of the natural
course of spontaneous regression and the existence of clinically occult
lesions. In addition, previous reports of fibrous lesions have not necessarily
been based on current classification schemes. There is a slight male
preponderance, and infantile myofibromatosis has rarely been observed in
adults.
The cause of the disease is unclear, although the presence of maternal
estrogen has been hypothesized. In addition, familial associations have been
described, which suggests an autosomal-dominant inheritance pattern.
Histologically, the fibrotic lesions are seen to contain whorls and loose
fascicles of spindle-shaped cells, myofibroblastic in origin, along the
periphery, with less well-differentiated cells centrally exhibiting a
hemangiopericytoma-like pattern. The presence of the central
hemangiopericytoma-like vascular spaces help differentiate infantile
myofibromatosis from entities such as digital fibromatosis, fibromatosis
colli, hyaline fibromatosis, fibrous hamartoma of infancy, calcifying
aponeurotic fibroma, and intravascular fasciitis.
Intracranial involvement of infantile myofibromatosis is rare and typically
is caused by cephalad extension of an extracranial process
[2,
7]. Intracranial lesions are
typically seen in the vicinity of the dura and infiltrate or erode the
adjacent calvarium [5].
Displacement and compression of the brain are also invariably present.
Intraparenchymal involvement has also been described, although less
frequently, and may involve the spine.
The current case is unique because its epicenter was clearly within the
posterior fossa, and the lesion extended extracranially via the jugular
foramen. Furthermore, although perivascular or angiocentric lesions are
characteristic of infantile myofibromatosis, intravascular invasion and
extension have not been described previously, to our knowledge. Our case
dramatically shows intravascular involvement of the jugular vein and
obliteration of the straight and sigmoid sinuses on the left.
Although this transjugular route of spread is unusual, we have observed
intravascular growth through the internal jugular vein with several
slow-growing, relatively benign tumors including two macroadenomas, a glomus
tumor, and a chondromyxoid fibroma of the posterior fossa. The incidence of
this route of spread is not known, but observation of this route of spread
will likely increase as radiologists become more familiar with the MRI
appearance of the jugular foramen region. It is important to interrogate the
jugular bulb and upper internal jugular vein whenever lesions near the jugular
foramen are encountered, especially if lower cranial neuropathies are found
clinically or radiographically. Although flow-related artifacts and anatomic
variations are problematic, identifying internal calcifications (as in this
case), intrinsic flow voids related to tumor vascularity, unusual enhancement,
or lack of normal enhancement within the internal jugular vein can help
suggest the diagnosis of tumor thrombus.
In summary, we report a case of an unusual manifestation of infantile
myofibromatosis. Although intracranial involvement is relatively rare, the
diagnosis of infantile myofibromatosis should be considered in young infants
with extraaxial tumors. Clues to the diagnosis include a history of cutaneous
or soft-tissue lesions and family history. Though imaging findings are not
specific, an enhancing, partially calcified, dural-based lesion with skull
base or calvarial destruction should suggest the possibility of infantile
myofibromatosis. In addition, this case brings attention to the possibility of
transjugular extension of intracranial tumor into the suprahyoid neck.
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Introduction
Case Report
