DOI:10.2214/AJR.05.0969
AJR 2006; 186:S449-S451
© American Roentgen Ray Society
AJR Teaching File: Enlarging Splenic Mass After Nephrectomy
Alvin C. Silva1
1 Department of Diagnostic Radiology, Mayo Clinic Scottsdale, 13400 E Shea
Blvd., Scottsdale, AZ 85259.
Received June 7, 2005;
accepted after revision August 18, 2005.
Address correspondence to A. C. Silva
(silva.alvin{at}mayo.edu).
Keywords: abdominal imaging • MRI • pseudotumor • spleen
Clinical History
An asymptomatic 74-year-old man presents with an enlarging splenic mass 3
years after right nephrectomy for renal cell carcinoma.
Radiologic Description
MR images show a well-defined splenic mass with T1 isointensity
(Fig. 1A) and mild
heterogeneous T2 hypointensity (Fig.
1B). After administration of a superparamagnetic iron oxide (SPIO)
contrast agent, the lesion does not decrease in T2 signal intensity
(Fig. 1C). After administration
of gadolinium contrast material, the arterial phase image shows early
peripheral enhancement with central stellate hypoenhancement
(Fig. 1D). On serial delayed
scans, heterogeneous peripheral enhancement and progressive enhancement of the
central stellate region remain (Figs.
1E and
1F).
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Fig. 1A —Inflammatory pseudotumor of the spleen in asymptomatic 74-year-old
man with history of remote renal carcinoma resection. Axial T1-weighted MR
image shows that mass (arrow) is isointense to splenic
parenchyma.
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Fig. 1B —Inflammatory pseudotumor of the spleen in asymptomatic 74-year-old
man with history of remote renal carcinoma resection. Axial T2-weighted MR
image with fat saturation shows well-defined mass (arrow) that is
mildly hypointense to splenic parenchyma.
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Fig. 1C —Inflammatory pseudotumor of the spleen in asymptomatic 74-year-old
man with history of remote renal carcinoma resection. Axial T2-weighted MR
image after administration of superparamagnetic iron oxide (SPIO) contrast
agent shows decreased signal involving liver and spleen. Because splenic mass
(arrow) does not take up SPIO contrast material, it remains
relatively increased in signal intensity.
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Fig. 1D —Inflammatory pseudotumor of the spleen in asymptomatic 74-year-old
man with history of remote renal carcinoma resection. Dynamic
gadolinium-enhanced images during arterial (D), portal venous
(E), and delayed (F) phases show heterogeneous peripheral early
enhancement (long arrows) and progressive central enhancement
(short arrows) that remains mildly hyperintense on subsequent delayed
phases.
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Fig. 1E —Inflammatory pseudotumor of the spleen in asymptomatic 74-year-old
man with history of remote renal carcinoma resection. Dynamic
gadolinium-enhanced images during arterial (D), portal venous
(E), and delayed (F) phases show heterogeneous peripheral early
enhancement (long arrows) and progressive central enhancement
(short arrows) that remains mildly hyperintense on subsequent delayed
phases.
|
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Fig. 1F —Inflammatory pseudotumor of the spleen in asymptomatic 74-year-old
man with history of remote renal carcinoma resection. Dynamic
gadolinium-enhanced images during arterial (D), portal venous
(E), and delayed (F) phases show heterogeneous peripheral early
enhancement (long arrows) and progressive central enhancement
(short arrows) that remains mildly hyperintense on subsequent delayed
phases.
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Differential Diagnosis
The differential diagnosis in this patient includes hemangioma, hamartoma,
inflammatory pseudotumor, and renal metastasis.
Diagnosis
The diagnosis in this patient is inflammatory pseudotumor.
Commentary
Inflammatory pseudotumor is a benign entity that has been observed in
virtually every organ but is extremely rare in the spleen. From its initial
description in 1984 [1] until
2000, only 64 cases have been reported worldwide
[2]. Although these lesions
occur predominantly in adults, inflammatory pseudotumor has recently been
reported occurring in a child
[3]. These lesions are usually
discovered incidentally; symptoms or abnormal laboratory values leading to
discovery are the exception
[3-5].
Histologically, inflammatory pseudotumors are composed of focal polymorphous
inflammatory cells, reparative fibroblastic stroma, and granulomatous
components. Their cause remains uncertain, but infectious or autoimmune
origins are considered.
On MRI, inflammatory pseudotumors are typically isointense on T1-weighted
sequences. T2 signal is variable, depending on the relative amounts of
cellular (T2 hyperintense) versus fibrous (T2 hypointense) tissue present.
Reported dynamic gadolinium-enhanced findings can also vary from early
peripheral arterial enhancement to delayed persistent enhancement
[1,
2,
6-8].
As in this patient, the presence of a central stellate T2 low signal, which
shows delayed progressive enhancement, has been reported to be strongly
suggestive of this entity [6].
An SPIO contrast agent will deposit within cells of the reticuloendothelial
system (RES), resulting in decreased signal on T2-weighted sequences
[9]. Because this lesion is not
composed of RES cells, it will appear to be increased in signal intensity
relative to normal splenic tissue.
The other entities in the differential diagnosis are unlikely. Although
hemangiomas are the most common benign splenic tumor, these lesions typically
show homogeneous T2 hyperintensity that persists on prolonged-echo T2-weighted
sequences. In addition, splenic hemangiomas will often display nodular
centripetal enhancement, similar to hepatic hemangiomas
[8,
10]. In contrast, hamartomas
typically exhibit heterogeneous T2 hyperintensity, with diffuse heterogeneous
early enhancement that becomes more uniform on delayed images. In addition,
hamartomas should decrease in T2 signal intensity after the administration of
SPIO contrast material because of their splenic tissue composition. Splenic
metastases are relatively uncommon, with isolated renal cell carcinoma
metastases extremely rare [8].
Furthermore, metastases to the spleen typically occur in the setting of
widespread disease.
Take-home pearl: Splenic masses are relatively rare and can be difficult to
diagnose prospectively. However, a knowledge of specific MR characteristics
can help narrow the differential considerations. In this regard, the following
points should be kept in mind: First, splenic hemangiomas generally have an
MRI appearance similar to hepatic hemangiomas. Second, splenic hamartomas are
anomalous mixtures of normal splenic tissue and will therefore decrease in
signal intensity after the administration of an SPIO contrast agent. Third,
surgical excision is generally required for splenic inflammatory pseudotumors
because their imaging characteristics are difficult to differentiate from
those of malignant neoplasms.
Objective
The educational objective of this teaching article is to describe the
typical MRI findings of inflammatory pseudotumor of the spleen.
Conclusion
Focal splenic masses are occasionally found during elective abdominal
imaging or the workup of other, extrasplenic conditions. Because the clinical
manifestations are unreliable, knowledge of the specific MRI characteristics
can be helpful in differentiating inflammatory pseudotumor from other
pathologic lesions involving the spleen.
References
- Cotelingam JD, Jaffe ES. Inflammatory pseudotumor of the spleen.
Am J Surg Pathol 1984;8
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- Monforte-Munoz H, Ro JY, Manning JT Jr, et al. Inflammatory
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- Rabushka LS, Kawashima A, Fishman EK. Imaging of the spleen: CT
with supplemental MR examination. RadioGraphics1994; 14:307
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- Wang YX, Hussain SM, Krestin GP. Superparamagnetic iron oxide
contrast agents: physicochemical characteristics and applications in MR
imaging. Eur Radiol 2001;11
: 2319-2331[CrossRef][Medline]
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Radiology 1997;202
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Clinical History
Radiologic Description
