AJR 2000; 175:495-501
© American Roentgen Ray Society
Retinoblastoma
Sonographic Findings with Pathologic Correlation in Pediatric Patients
S. C. Kaste1,2,
J. J. Jenkins, III3,
C. B. Pratt4,
J. W. Langston1,2 and
B. G. Haik5,6
1
Department of Diagnostic Imaging, St. Jude Children's Research Hospital, 332
N. Lauderdale, Memphis, TN 38105-2794.
2
Department of Radiology, University of Tennessee at Memphis, 865 Jefferson
Ave., Memphis, TN 38163.
3
Department of Pathology and Laboratory Medicine, St. Jude Children's Resarch
Hospital, Memphis, TN 38105-2794.
4
Department of Hematology-Oncology, St. Jude Children's Research Hospital,
Memphis, TN 38105-2794.
5
Department of Surgery, Division of Ophthalmology, St. Jude Children's Research
Hospital, Memphis, TN 38105-2794.
6
Department of Ophthalmology, University of Tennessee at Memphis, Memphis, TN
38163.
Received November 11, 1999;
accepted after revision January 13, 2000.
Presented at the annual meeting of the Society for Pediatric Radiology,
Vancouver, B. C., May 1999.
Supported in part by grants P30 CA-21765 and CA-23099 from the National
Cancer Institute and by the American Lebanese Syrian Associated Charities.
Address correspondence to S. C. Kaste.
Introduction
Retinoblastoma, a small round-cell tumor arising from neuroepithelial
cells, is the most common childhood intraocular malignancy
[1,
2]. Approximately 200 cases are
diagnosed per year in the United States. The average age at diagnosis is 18
months with 80% of cases occurring before 3-4 years old
[1]. Approximately 30% are
bilateral and are typically diagnosed earlier than unilateral cases. Lesions
may be synchronous, metachronous, unifocal, or multifocal. Most (90%) new
cases of retinoblastoma are sporadic and 10% are inherited. Inherited
retinoblastoma has an autosomal dominant pattern of inheritance with 80-100%
penetrance. Sporadic lesions usually result from spontaneous mutation
[1].
Diagnosis is typically by ophthalmologic examination, prompted by
leukocoria or "white reflex"
[1,
3] seen in 60% of patients
[3]. Leukocoria is associated
with large tumors or total retinal detachment
[1]. Until recently, imaging
techniques have lacked resolution capabilities that could approach the
ophthalmologic examination. Thus, few radiologists are integrally involved
with ocular imaging, especially in children. Herein we review normal ocular
anatomy (Figs. 1 and
2A,2B,2C),
retinoblastoma pathophysiology, and its sonographic appearance.
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Fig. 1. —Transverse drawing shows normal anatomy of ocular globe. Anterior
chamber lies anterior to lens, extends from cornea to iris, and contains
anechoic aqueous humor. Posterior chamber extends from iris to posterior
aspect of lens and contains anechoic aqueous humor. Vitreous chamber lies
posterior to lens and extends from posterior surface of lens to ocular
surface. Posterior ocular surface has three layers: inner retina, vascular
choroid, and tougher outer sclera. Suspensory ligaments support lens and arise
from vascular ciliary bodies. Ora serrata represents anteriormost extent of
retina and covers posterior two thirds of inner surface of posterior chamber.
Optic nerve extends posteriorly from globe within retroorbital fat. Central
retinal artery and vein course through optic nerve.
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Fig. 2A. Transverse real-time sonograms through globes of healthy subjects.
Transverse sonogram of infant boy shows intact cornea (1), covered by closed
eyelid (2). Iris (3) is seen as incomplete echogenic structures posterior to
anechoic aqueous humor of anterior chamber (4). Lens (5) is anechoic and
delineated by reflective echogenic anterior and posterior surfaces. Anechoic
vitreous chamber or vitreous body (6) extends from posterior lens to ocular
surface. Echogenic retroorbital fat (7) delineates posterior surface of
globe.
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Fig. 2B. Transverse real-time sonograms through globes of healthy subjects.
Transverse sonogram of globe of infant boy shows closed eyelid (1) covering
anterior scleral surface (2). Anechoic vitreous chamber (3) contrasts small
nonshadowing echogenic "mound" of optic nerve head (4) that may be
confused with small mass. Echogenic retroorbital fat (5) surrounds hypoechoic
optic nerve (6).
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Fig. 2C. Transverse real-time sonograms through globes of healthy subjects.
Transverse power Doppler sonogram of 3-year-old girl through level of optic
nerve shows normal choroidal vessels (1), ophthalmic vein (2), and portion of
ophthalmic artery (3). Central retinal artery (4) courses through hypoechoic
optic nerve (5).
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Patterns of Tumor Growth
Retinoblastoma shows three patterns of tumor growth. An endophytic tumor
breaks through the retina and grows into the vitreous chamber. An exophytic
tumor originates in the retina and grows into the subretinal space. A diffuse
infiltrating tumor is growth-limited to the retina and typically lacks
calcification, is seen in older patients, and more readily simulates
inflammatory or hemorrhagic processes
[1,
2]. Most tumors exhibit both
exophytic and endophytic growth
[1]. Retinal detachment (Figs.
3A,3B,3C,3D,4A,4B,4C,4D,4E,4F,4G,5A,5B)
and vitreal tumor seeding may occur with any form. Differentiation between
multifocal lesions and tumor seeding may be difficult
[1] (Figs.
3A,3B,3C,3D,4A,4B,4C,4D,4E,4F,4G,5A,5B).
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Fig. 3A. —3-year-old boy with retinoblastoma of left globe presented with
leukocoria and medial deviation of globe. Transverse real-time sonogram shows
clear anterior chamber (1) but abnormal thickening of cornea (2). Posterior
reflective surface of lens (3) is contrasted with clear vitreous. Ciliary
apparatus (4) abuts large densely echogenic mass (5) occupying nearly entire
vitreous chamber. Posterior shadowing was absent, suggesting absence of
calcification. Tumor covered optic nerve head, raising concern about extension
beyond globe. Mass abuts posterior surface of lens and approaches ciliary
apparatus temporally. Echogenic debris is present nasally, suggesting
hemorrhage.
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Fig. 3B. —3-year-old boy with retinoblastoma of left globe presented with
leukocoria and medial deviation of globe. Longitudinal sonogram shows normal
anterior chamber (1) and posterior reflective surface of lens (2). Retina (3)
is reflected away from its normal position. Subretinal hemorrhage (4) is
better shown on this longitudinal image than on A as thick rim of
decreased echogenicity lying deep in relation to retina. Retina is detached by
hemorrhage and tumor.
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Fig. 3C. —3-year-old boy with retinoblastoma of left globe presented with
leukocoria and medial deviation of globe. Photograph of gross pathologic
specimen of globe shows normal cornea (1), anterior chamber (2), and lens (3).
Soft friable white-gray tumor (4) located predominantly along temporal aspect
of globe lacks gross calcifications. Mass uplifts retina (5) and is associated
with subretinal exudate (6). Temporally, red-brown hemorrhage extends
subchoroidally and opposes friable tumor. Optic nerve (7) is free of
tumor.
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Fig. 3D. —3-year-old boy with retinoblastoma of left globe presented with
leukocoria and medial deviation of globe. Microscopically, cornea (1),
anterior chamber (2), ciliary apparatus (3), iris (4), ora serrata (5), and
lens (6) are normal. Large cellular small round-cell tumor (7) located nasally
shows numerous areas of mitotic activity and large areas of confluent
geographic necrosis with acute inflammation. Tumor appears to be multifocal
with several nests abutting choroid. Retina is detached (8). Massive
subretinal exudate (9) with hemosiderin is shown. Choroid temporally (10) is
normal but involved nasally with multifocal tumors (11). Tumor is attached to
optic nerve head (12) but is not invading optic nerve itself (13). (H and
E,x5)
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Fig. 4A. —3-year-old boy presented with left-sided leukocoria and vision loss
of 2-month duration. Axial sonogram through mid globe shows normal cornea (1),
anterior chamber (2), and lens (3). Retina (4) is detached by large
inhomogeneously enhancing echogenic mass occupying most of vitreous chamber.
Subretinal exudate (6) is seen as nasal rim of hypoechoic material. Retinal
leaflets appear as stippled echogenic curves. Tumor extends from posterior
surface of lens (3), covers optic nerve head, is associated with retinal
detachment, and contains large area of dense calcifications. Optic nerve (7)
is tumor free.
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Fig. 4B. —3-year-old boy presented with left-sided leukocoria and vision loss
of 2-month duration. Axial sonogram through inferior portion of left globe
shows detached retinal leaflets (1). Dense calcifications with posterior
shadowing (2) are shown to better advantage. Subretinal exudate (3) is seen as
hypoechoic material along nasal aspect of globe. Posterior scleral surface (4)
is well shown.
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Fig. 4C. —3-year-old boy presented with left-sided leukocoria and vision loss
of 2-month duration. Axial contrast-enhanced CT scan shows normal lens (1),
subtle rim of intermediate attenuation indicative of subretinal exudate (2),
and partially calcified mildly enhancing soft-tissue mass (3) occupying mid
globe, covering optic nerve head, and extending to posterior surface of
lens.
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Fig. 4D. —3-year-old boy presented with left-sided leukocoria and vision loss
of 2-month duration. Axial T2-weighted MR image through mid globe shows normal
cornea (1) and lens (2). Large mass in left globe extending from optic nerve
head to lens is associated with hemorrhage (3). Subretinal exudate (4) is
bright on this T2-weighted image.
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Fig. 4E. —3-year-old boy presented with left-sided leukocoria and vision loss
of 2-month duration. "Frog eye" view
[8] shows normally enhancing
sclera (1). Gelatinous exudate (2) overlies enhancing mass (4) occupying lower
two thirds of globe, covering optic nerve head (3), and extending to lens.
Optic nerve itself appears normal.
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Fig. 4F. —3-year-old boy presented with left-sided leukocoria and vision loss
of 2-month duration. Photograph of gross examination of globe confirms normal
cornea (1), anterior chamber (2), and lens (3). Tumor extends to optic nerve
and inverts lens (4) but without extension into anterior chamber. Hemorrhage
(5) is present with large tumor (6) occupying most of vitreous chamber.
Superior portion of globe is filled with gelatinous subretinal exudate (7).
Optic nerve is spared (8).
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Fig. 4G. —3-year-old boy presented with left-sided leukocoria and vision loss
of 2-month duration. Microscopically, cornea (1), anterior chamber (2), and
lens (3) are normal. Hemorrhage (4) is shown in mass. Tumor extends anteriorly
to lens (5). Subretinal exudate (6) outlines temporal aspect of globe. Choroid
(7) and sclera (8) are normal. Retina is detached (9). Optic nerve is normal
(10) but tumor invades optic papillae (11). (H and E,x5)
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Fig. 5A. —17-month-old boy with leukocoria and strabismus of right eye.
Transverse sonogram shows retinal leaflet (1) with small collection of
subretinal exudate (2). Tumor extends to ciliary body (3). Densely calcified
mass (4) fills approximately 80% of vitreous chamber, extends to posterior
retinal surface, and obscures visualization of optic nerve. Only scant clear
vitreous remains (5).
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Fig. 5B. —17-month-old boy with leukocoria and strabismus of right eye.
Photograph of transverse gross section through mid globe shows iris (1),
anterior chamber (2) compressed by mass effect on iris, and lens (3) distorted
by mass that extends to ciliary body (4) temporally. Subretinal exudate (5)
occupies nasal aspect of globe. Large white-tan tumor (6) nearly fills
vitreous body and has focal areas of necrosis, calcification, and hemorrhage.
Sclera (7) is intact and optic nerve (8) is uninvolved. Multifocal disease was
shown microscopically (not shown).
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Intraocular tumor spread (Figs.
3A,3B,3C,3D,
6A,6B,6C,6D,
and
7A,7B,7C)
exposes the tumor cells to rich vascularity (Fig.
6A,6B,6C,6D),
potentially leading to widespread hematogenous metastases. Extraocular disease
occurs from hematogenous or lymphatic spread, via scleral veins directly into
the orbit or by optic nerve invasion (Figs.
5A,5B
and
7A,7B,7C).
MR imaging or CT best delineates the resulting intracranial spread
[1]. Color Doppler imaging can
identify and monitor tumor viability (Fig.
8A,8B).
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Fig. 6A. —2-year-old girl presented with retinoblastoma of right eye. Axial
sonogram through mid plane of right globe shows densely echogenic mass
occupying most of vitreous chamber with focal central area of shadowing
calcification (1). Extensive retinal detachment (2) is seen as thin line of
medium echogenicity overlying subretinal exudate (3) along temporal aspect of
globe. Mass covers and bulges into optic nerve head (4) suggesting invasion.
Optic nerve (5) is seen as hypoechoic area surrounded by echogenic fat.
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Fig. 6B. —2-year-old girl presented with retinoblastoma of right eye.
Longitudinal sonogram shows extensive retinal detachment (1) and moderately
echogenic subretinal exudate (2). In overlying tumor (3), retinal leaflets
appear as string of echogenic "pearls."
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Fig. 6C. —2-year-old girl presented with retinoblastoma of right eye.
Contrast-enhanced axial CT scan shows normal lens (1) and mildly enhancing
centrally calcified mass occupying most of vitreous chamber (2). Subretinal
exudate (3) is seen as intermediate density tracking along temporal portion of
globe. Tumor extension to posterior surface of lens is not as well shown.
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Fig. 6D. —2-year-old girl presented with retinoblastoma of right eye.
Photograph of mid plane gross specimen shows large soft fragile white-gray
exophytic tumor (1) largely filling vitreous chamber and covering and
extending into optic nerve head. Focal areas of necrosis are seen. Temporal
retinal detachment is visible with yellow gelatinous exudate (2). Retina (3)
is in normal position.
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Fig. 7A. —27-month-old boy with leukocoria of left eye. Transverse sonogram
shows normal lens (1) and minimal residual clear vitreous (2). Synechiae (3)
extend from inhomogeneous echogenic mass (4) nearly filling vitreous chamber.
Scattered areas of posterior shadowing imply calcifications. Retinal
detachment (5) is delineated by echogenic leaflets covering extensive
subretinal disease (6). Although optic nerve (7) is only partially visible,
tumor appears to extend into optic papilla (8).
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Fig. 7B. —27-month-old boy with leukocoria of left eye. Photograph of gross
calotte through level of pupil and lens shows normal anterior chamber (1) and
lens (2). Bulky white-gray tumor fills most of vitreous chamber. Adhesion (3)
extends from tumor to lens. Residual clear vitreous (4) is sparse. Retinal
surface is uplifted (5) and thickened by nodular white tumor exudate (6).
Tumor extends into choroid (7) and covers optic nerve (8).
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Fig. 7C. —27-month-old boy with leukocoria of left eye. Microscopic
examination shows tumor adhesion (1) to lens (2). Posteriorly, large tumor
plaque invades choroid (3), uplifting retina (4) but sparing underlying sclera
(5). Large tumor (6) occupies most of vitreous chamber with little remaining
clear vitreous (7). Sclera is normal (8) and optic nerve (9) is covered by
tumor. (H and E,x5)
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Fig. 8A. —8-month-old boy with bilateral retinoblastoma was enrolled on
chemoreduction protocol to avoid enucleation and preserve vision. Transverse
color Doppler sonograms through mid plane of both globes show intense tumor
vascularity arising bilaterally from central retinal vessels to supply
posterior retinal masses. Transverse sonogram of right globe shows normal
cornea (1), lens (2), and clear vitreous (3). Small tumor mass (4) (0.52
x 0.36 cm) with intense central vascularity arises from posterior
retina. Normal choroidal vessels (5) extend from optic papilla (6). Central
retinal vessels (7) course through optic nerve. Ophthalmic vessels (8) course
along outside of optic nerve.
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Fig. 8B. —8-month-old boy with bilateral retinoblastoma was enrolled on
chemoreduction protocol to avoid enucleation and preserve vision. Transverse
color Doppler sonograms through mid plane of both globes show intense tumor
vascularity arising bilaterally from central retinal vessels to supply
posterior retinal masses. Transverse sonogram of left globe shows large mass
in vitreous chamber, extending to lens (1). Echogenic artifact (2) extends
from mass to ciliary body. Note marked asymmetry in size of masses with that
on left being much larger (1.4 x 1.1 x 1.4 cm) than that on right.
Retinal detachment is seen as uplifted and thickened retinal leaflet (3)
overlying extensive echogenic subretinal exudate (4).
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Role of Imaging in Retinoblastoma
Direct ophthalmologic visualization is most sensitive and specific for
determining intraocular disease status and therapeutic response; like CT and
MR imaging, such examinations typically require general anesthesia. Clinical
staging includes CT and MR imaging of the orbits and brain
[2]. High-resolution real-time
and Doppler sonography of the orbits defines intraocular disease extent,
monitors therapeutic response, and clarifies CT or MR imaging. The smaller
contemporary high-resolution probes better fit the pediatric orbit and provide
greater resolution and image details than previous devices. Orbital sonography
is particularly attractive because it lacks ionizing radiation, is painless
and versatile, can be performed without sedation, and is typically more
readily available than other imaging techniques or ophthalmologic examinations
performed under anesthesia. Sonography can also examine intraocular contents
when the anterior chamber is clouded by cataracts, disease, and hyphema that
preclude ophthalmologic examination
[3] (Fig.
9A,9B,9C,9D).
Thus, the roles of imaging are to confirm the ophthalmologic diagnosis,
determine intra- and extraocular disease extent, and characterize tumor
response [2,
3]. Assessment of optic nerve
involvement and intracranial extent of disease and identification of distant
metastases are particularly important in patients with retinoblastoma.
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Fig. 9A. —1-year-old boy, who re-presented 3 weeks prior with history of
resolved vitreous hemorrhage in left eye and eyelid swelling, shows clinical
and imaging evidence of tumor regression. He was treated with radiation
therapy for bilateral retinoblastoma at 3 months old. Transverse real-time
sonogram shows abnormally thickened retina (1) at ora serrata (2). Subretinal
exudate (3) is isoechoic with noncalcified portions of mass. Large densely
calcified mass (4) nearly completely filling vitreous chamber of left globe
extends to lens and abuts ora serrata nasally. This mass had also increased in
size compared with prior imaging. Echogenic material, separate from mass (5),
suggests subretinal hemorrhage. Calcifications obscure visualization of optic
nerve, and child's irritability precluded color Doppler imaging.
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Fig. 9B. —1-year-old boy, who re-presented 3 weeks prior with history of
resolved vitreous hemorrhage in left eye and eyelid swelling, shows clinical
and imaging evidence of tumor regression. He was treated with radiation
therapy for bilateral retinoblastoma at 3 months old. Axial unenhanced
T1-weighted MR image through mid globes shows normal anterior chamber (1).
Subretinal exudate (2) is of intermediate signal intensity. Large partially
calcified mass (3) occupies most of vitreous chamber of left globe. Note
previously treated focus of inactive retinoblastoma in right globe (4).
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Fig. 9C. —1-year-old boy, who re-presented 3 weeks prior with history of
resolved vitreous hemorrhage in left eye and eyelid swelling, shows clinical
and imaging evidence of tumor regression. He was treated with radiation
therapy for bilateral retinoblastoma at 3 months old. Contrast-enhanced
T1-weighted MR image through same level as B shows normal lens (1).
Small amount of vitreous has increased signal (2). Subretinal exudate (3) has
decreased signal compared with vitreous. Enhancing portion of active tumor (4)
lies posterior to calcified portion of mass (5) and covers optic nerve
head.
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Fig. 9D. —1-year-old boy, who re-presented 3 weeks prior with history of
resolved vitreous hemorrhage in left eye and eyelid swelling, shows clinical
and imaging evidence of tumor regression. He was treated with radiation
therapy for bilateral retinoblastoma at 3 months old. Photograph of axial
gross specimen shows normal cornea (1) and lens (2). Retinal detachment (3)
with subretinal exudate indents vitreous chamber (4) filled with clotted
blood. Smaller tumor focus (5) is located temporally. Large densely calcified
retinoblastoma (6) overlaps edge of optic disc, uplifts retina (7), and spares
optic nerve (8). Microscopically (not shown), extensive choroidal invasion by
tumor and tumor thrombi within choroidal vessels was seen.
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Imaging Appearance of Retinoblastoma
Sonography
Orbital sonography provides superb intraocular detail and allows sequential
study without ionizing radiation. This technique is limited to study of the
globe and anterior orbit, is hampered by intraocular calcifications, and is
degraded by patient motion. Retinal detachment with hemorrhage may obscure
concurrent retinoblastoma lesions. The mobility of sonographic equipment is
advantageous for intraoperative imaging performed in concert with
ophthalmologic examination.
We perform sonography with the patient in a comfortable position, usually
recumbent. However, the versatility of sonography allows patient scanning
while in a stroller, on a parent's shoulder, or in a parent's lap. Scanning is
performed by direct contact on a closed eyelid after applying warm sterile
gel. Only light pressure is used because excessive ocular pressure can cause
bradycardia and induce pain. We use a 15L8 multihertz transducer (Acuson,
Mountain View, CA) at 13 MHz with color and power Doppler capability; power up
to -3 dB falls within published guidelines
[4]. Transverse and
longitudinal planes usually provide exquisite tumor detail. A standoff pad may
aid assessment of near-field structures
[2].
Retinoblastoma appears as an echogenic soft-tissue mass with various
degrees of calcification [2].
The vascularity indicates tumor activity; that is, lesions are hypervascular
at diagnosis (Fig.
8A,8B)
and when active. Vascularity regresses with treatment. Tumors tend to outgrow
their blood supply resulting in areas of necrosis
[1,
2]. The vitreous may have
echogenic debris from hemorrhage, increased globulin content, or tumor seeding
[5] (Figs.
3A,3B,3C,3D,
4A,4B,4C,4D,4E,4F,4G,
and
9A,9B,9C,9D).
Synechiae in the vitreous may develop during treatment or be present at
diagnosis.
CT
CT detects intraocular, extraocular, and intracranial disease extension;
excels at delineation of bony abnormalities; and readily depicts tumoral
calcifications. Delineation of intraocular soft-tissue detail is limited with
CT. Contrast enhancement is typically used but may obscure underlying
calcifications unless preceded by a nonenhanced study (Figs.
4A,4B,4C,4D,4E,4F,4G
and
6A,6B,6C,6D).
On CT, retinoblastoma is characterized by enhancing intermediate-density
soft-tissue mass or masses, with varying degrees of calcification;
calcification increases with therapeutic response. The vitreous may be
abnormally dense from debris, hemorrhage, or increased globulin content.
Differentiation between noncalcified tumor and hemorrhage may be
difficult.
MR Imaging
MR imaging adds biochemical characterization to the structural depiction of
ocular, orbital, and intracranial abnormality, thus introducing an additional
level of differential criteria. The multiplanar capabilities of MR imaging
provide detailed examination of tumors and retrobulbar and intracranial
structures.
Retinoblastoma is a heterogeneously enhancing soft-tissue mass with various
degrees of calcification on MR imaging. Lesions are typically hyperintense to
vitreous on T1-weighted sequences and hypointense to vitreous on T2-weighted
sequences [2]. The vitreous may
be abnormally bright on T1-weighted sequences because of increased globulin
content and a decreased ratio of albumin to globulin that occurs with
malignancy [6] (Fig.
8A,8B).
Calcifications and lesions smaller than 2 mm are unreliably revealed with MR
imaging [2].
Treatment
Standard therapy comprises enucleation for unilateral disease and radiation
therapy with or without enucleation for bilateral disease. However,
contemporary treatment for retinoblastoma is transitioning to front-line
chemotherapy to improve disease control while preserving vision and minimizing
adverse sequelae of enucleation and radiation therapy
[6]. Retinoblastoma contracts,
calcifies, and becomes hypovascular in response to therapy
[7]. To understand sonographic
characteristics of retinoblastoma, we correlated imaging and pathologic
findings of children with retinoblastoma who underwent enucleation. Selected
CT and MR images are included.
References
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Poplack DG, eds. Principles and practice of pediatric
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Kaufman LM, Mafee MF, Song CD. Retinoblastoma and simulating
lesions: role of CT, MR imaging and use of Gd-DTPA contrast enhancement.
Radiol Clin North Am
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Remit FG, Slovis TL, Baker JD. Orbital sonography in children.
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Introduction
Patterns of Tumor Growth
