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EDUCATION EXHIBIT
1151
Imaging of Renal
Lymphoma: Patterns of
Disease with Pathologic
Correlation1
CME FEATURE
See accompanying
test at http://
www.rsna.org
/education
/rg_cme.html
LEARNING
OBJECTIVES
FOR TEST 5
After reading this
article and taking
the test, the reader
will be able to:
䡲 Identify both typical and atypical radiologic patterns seen
in renal lymphoma.
䡲 List the diagnostic
options in the differential diagnosis of
renal lymphoma.
䡲 Discuss the role of
imaging-guided percutaneous biopsy in
the management of
suspected renal lymphoma.
TEACHING
POINTS
See last page
Sheila Sheth, MD ● Syed Ali, MD ● Elliot Fishman, MD
Extranodal spread of lymphoma often affects the genitourinary system,
with the kidneys being the most commonly involved organs. Contrast
material– enhanced computed tomography (CT) remains the modality
of choice for the detection, diagnosis, staging, and monitoring of renal
lymphoma. Magnetic resonance (MR) imaging is particularly useful in
patients in whom intravenous administration of iodinated contrast material is contraindicated. Ultrasonography (US), although very valuable
for diagnosing lymphoma in the testis or epididymis, is less sensitive
than CT and MR imaging for detecting renal lymphoma. Typical imaging findings of renal lymphoma include multiple poorly enhancing or
hypoechoic masses, retroperitoneal tumors directly invading the kidneys, bilateral renal enlargement, and perirenal soft-tissue masses. Cystic lesions and tumors predominantly affecting the renal sinus and collecting system are uncommon. Unless the renal lesions manifest in the
setting of widespread lymphoma, percutaneous biopsy is indicated to
differentiate lymphoma from metastases, hypovascular renal cell carcinoma, uroepithelial carcinoma, or atypical infection, with US routinely
being used to guide the procedure. Current immunohistochemical
techniques allow accurate diagnosis and characterization of renal lymphoma. Radiologists should be familiar with both typical and atypical
manifestations of renal lymphoma and should recommend imagingguided percutaneous biopsy for diagnostic confirmation to avoid unnecessary nephrectomy.
©
RSNA, 2006
Abbreviations: FDG ⫽ fluorodeoxyglucose, H-E ⫽ hematoxylin-eosin, HIV ⫽ human immunodeficiency virus
RadioGraphics 2006; 26:1151–1168 ● Published online 10.1148/rg.264055125 ● Content Codes:
1From
the Russell H. Morgan Department of Radiology and Radiological Science (S.S., E.F.) and the Department of Pathology (S.A.), Johns Hopkins
University, 600 N Wolfe St, Baltimore, MD 21287. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received May 31, 2005;
revision requested June 24 and received July 27; accepted August 4. All authors have no financial relationships to disclose. Address correspondence
to S.S. (e-mail: [email protected]).
©
RSNA, 2006
July-August 2006
Introduction
Teaching
Point
The genitourinary system is often affected by extranodal spread of lymphoma, being the second
most commonly affected anatomic entity next to
the hematopoietic and reticuloendothelial organs
(1). The kidneys are most commonly involved.
Reports from autopsy series of patients who have
succumbed to the disease describe foci of lymphoma in the kidneys in approximately one-third
of cases (1,2). In one series of 322 autopsies, lymphoma involved the kidneys in 37.6% of cases but
the urinary bladder and testes in only 8.4% and
5.9% of cases, respectively (2). Despite the relatively high prevalence of renal involvement, imaging studies demonstrate renal abnormalities in
only 3%– 8% of patients undergoing routine
evaluation for staging or during the course of
therapy (3–5). This apparent discrepancy between the pathology literature and the radiology
literature can be explained by several factors: Renal lymphoma is often poorly documented, since
the disease is often clinically silent and renal biopsy is rarely indicated to confirm the diagnosis in
the context of systemic disease. Furthermore, the
statistics cited earlier were gathered before the
widespread use of helical single– and multi– detector row computed tomography (CT), at a time
when findings were obtained with older-generation scanners and led to underestimation of the
prevalence of renal lesions. For example, in a
study of 225 patients with a diagnosis of lymphoma, only 11 (4.9%) had renal abnormalities at
staging examination performed on a conventional
CT scanner following intravenous drip infusion of
contrast material (6). In a more recently published pediatric series, renal manifestations of
lymphoma were detected in 11 (8%) of 139 children (7). It is anticipated that the superior evaluation of the renal parenchyma afforded by modern
imaging techniques will greatly improve the detection of renal lymphoma (5,7). When renal lymphoma occurs in the setting of disseminated disease, particularly nodal enlargement, the diagnosis is generally easily made. In a smaller number
of cases, however, the kidneys are predominantly
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or exclusively affected. In these cases, it is essential that the radiologist be able to recognize specific patterns of involvement that can suggest the
diagnosis and prevent unnecessary surgery.
In this article, we discuss the clinical manifestations of renal lymphoma and the imaging techniques used to evaluate affected patients. We also
discuss radiologic-pathologic correlation and various imaging patterns (multiple lesions, solitary
lesion, direct extension from retroperitoneal adenopathy, perinephric disease, nephromegaly,
renal sinus involvement) seen in renal lymphoma.
In addition, we briefly discuss the diagnostic role
of imaging-guided renal biopsy in this setting.
Clinical Manifestations
Renal lymphoma usually occurs in the setting of
widespread non-Hodgkin lymphoma, typically
B-cell type intermediate- and high-grade tumors
or American Burkitt lymphoma (8,9). In more
than one-half of cases, renal or perirenal spread is
detected at initial presentation (Fig 1) (4). Involvement by Hodgkin disease is much less common, being seen in less than 1% of patients at
presentation (2,5,10). In the majority of cases,
renal lymphoma is clinically asymptomatic and
radiologic detection seldom influences staging
and treatment. Follow-up data obtained in patients with renal lymphoma suggest that, although
involvement of the kidneys at the time of presentation does not necessarily indicate a poor prognosis, recurrence in the kidney is associated with
an increased mortality rate (9).
Immunocompromised patients are at significantly higher risk for developing lymphoma. In
this population, lymphomas develop as a consequence of the unrestricted proliferation of B
lymphocytes infected by Epstein-Barr virus. Extranodal lymphoma, including renal lymphoma—
either isolated or as part of multiple organ involvement—is particularly common (11,12). In
patients with HIV infection–acquired immunodeficiency syndrome, the prevalence of some types
of non-Hodgkin lymphoma, particularly the immunoblastic and Burkitt subtypes, is at least 113–
165 times greater than in the general population
(13) and increases with the decreasing CD4 lymphocyte count at presentation (14). Recipients of
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Figure 1. High-grade B-cell lymphoma in a 38-year-old human immunodeficiency virus (HIV)–positive
woman who presented with abdominal pain and distention. (a) Contrast material– enhanced CT scan of the
midabdomen shows a very large soft-tissue mass (arrows) infiltrating the mesentery and omentum and displacing the small bowel and colon. (b) Contrast-enhanced CT scan shows hypoenhancing soft-tissue masses (arrows) in both kidneys. Note also the retroperitoneal adenopathy (arrowhead). (c) Photomicrograph (original
magnification, ⫻200; Diff-Quik stain) of a specimen obtained at fine-needle aspiration biopsy shows hypercellularity with a uniform population of malignant lymphocytes. Numerous aptotic cells are also seen, a finding that is
compatible with a high-grade phenotype.
solid organ transplants also tend to develop aggressive non-Hodgkin lymphoma. One recently
published large analysis of almost 200,000 organ
transplant recipients by Opelz and Dohler (15)
helped confirm that these patients are at higher
risk than the general population. The incidence of
posttransplantation lymphoproliferative disorders
is highest during the 1st year following the procedure. This risk varies with the type of organ trans-
planted, varying from a 20-fold increase for recipients of renal transplants to a 120-fold increase
for recipients of combined heart-lung and lung
transplants (15). Most posttransplantation lymphomas are linked to uncontrolled Epstein-Barr
proliferation caused by immunosuppressive
therapy and tend to develop within or near the
allograft (15). The study by Opelz and Dohler
also emphasized the persistent long-term risk of
developing lymphoma run by transplant recipients.
In rare cases, diffuse infiltration of both kidneys by malignant lymphocytes may be the predominant or even the sole manifestation of the
disease. Patients present with flank pain, hematuria, or nonspecific symptoms of fever and night
sweats (16,17). Extensive lymphomatous infiltration of the renal parenchyma and compression of
the normal tubules can lead to acute renal failure
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(Fig 2) (17–19). Primary renal lymphoma that is
isolated to the renal parenchyma with no systemic
manifestations is uncommon, accounting for less
than 1% of cases of extranodal lymphoma (17).
Its origin is somewhat uncertain. Because the renal parenchyma does not normally contain lymphoid tissue, several mechanisms have been postulated to account for the development of lymphoma in the kidney: The tumor may originate in
the lymphatic-rich renal capsule or the perinephric fat and invade the parenchyma, or it can arise
from lymphocytes present in areas of chronic inflammation (17,20,21). The tumor is usually a
B-cell non-Hodgkin lymphoma and affects patients who are middle aged or older. The diagnosis of primary renal lymphoma is confirmed with
percutaneous biopsy of the renal parenchyma.
Rapid improvement in renal function and decrease in renal size follow the initiation of chemotherapy.
Imaging Techniques
Computed Tomography
Teaching
Point
Multi– detector row CT is the imaging modality
of choice for the evaluation of patients with suspected renal lymphoma. This modality not only
depicts the renal lesions, but also most accurately
helps identify extension to adjacent anatomic
structures such as the perirenal space and the retroperitoneum, thereby helping to determine the
systemic spread of the disease. The administration of intravenous contrast material and image
acquisition in the nephrographic (venous) phase
of enhancement are essential for the detection of
subtle or small lesions, particularly those in the
medullary portion of the kidney (Fig 1) (22).
Lymphomatous deposits tend to be hypovascular
and to enhance poorly. Thus, small masses that
do not deform the renal contour can be mistaken
for the unenhanced normal medulla and are less
conspicuous on early images obtained in the corticomedullary (late arterial) phase of enhancement. However, imaging during this phase allows
optimal depiction of the renal vessels and is im-
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portant for differentiating renal lymphoma from
hypervascular primary renal tumors. If the tumor
is predominantly central and affects the hilar region or the collecting system appears to be involved, excretory phase imaging is necessary. Excretory phase imaging also best demonstrates
obstruction of the collecting system by retroperitoneal masses.
Magnetic Resonance Imaging
Although the role of magnetic resonance (MR)
imaging in renal lymphoma is less clearly documented in the literature, small series have shown
MR imaging to be as accurate as contrast-enhanced CT in demonstrating renal and perirenal
disease (23). MR imaging is the optimal imaging
modality in patients with iodinated contrast material allergy or renal insufficiency. In addition, MR
imaging has proved superior to CT in depicting
involvement of the bone marrow (24,25). Like
most malignant and inflammatory renal lesions,
lymphoma exhibits hypointense signal on T1weighted MR images and is slightly hypointense
or isointense relative to normal renal cortex on
T2-weighted images. After the intravenous administration of gadolinium-based contrast material, lymphomatous deposits enhance less than
the surrounding normal parenchyma, although
some lesions demonstrate progressive enhancement on delayed images (Fig 2c, 2d) (24).
Ultrasonography
Both contrast-enhanced CT and MR imaging are
superior to US in detecting the presence of disease as well as the number of renal lesions and the
presence of extrarenal tumors (23,26,27). However, US may be the first test requested in patients who present with renal insufficiency or
flank pain; consequently, it is important to recognize the relatively subtle US abnormalities caused
by lymphoma (Fig 2a, 2b). US is also helpful in
patients who are unable to receive intravenous
iodinated contrast material. At our institution,
US is the ideal guidance modality for percutaneous biopsy, which, with the refinement of immunohistochemical and flow cytometric studies, allows specific diagnosis in the majority of cases
(Fig 2) (28).
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Figure 2. Burkitt-like aggressive lymphoma in a 40-year-old man who presented with right flank pain and a
creatinine level of 9.9. A diagnosis of HIV infection had recently been made. (a) Sagittal ultrasonographic
(US) image shows an enlarged left kidney with heterogeneous echotexture of the parenchyma. No discrete
mass is seen, and the normal shape of the kidney is preserved. (b) Sagittal US image of the right kidney shows
similar findings. In addition, there is ill-defined infiltration of the renal sinus fat near the lower pole and a focal
hypoechoic mass (arrows) in the lower pole. (c, d) Axial venous phase contrast-enhanced fat-saturated T1weighted (c) and coronal venous phase contrast-enhanced (d) MR images of the abdomen show left renal lesions (thin arrows) with very little enhancement. The mass in the lower pole of the right kidney (thick arrows)
has heterogeneous signal intensity. Note also the area of necrosis (arrowhead in c) within the mass. (e) Photomicrograph (original magnification, ⫻400; Diff-Quik stain) of a specimen obtained at fine-needle aspiration
biopsy shows intermediate-sized atypical lymphocytes with cytoplasmic vacuolization (arrow). The nuclei lack
prominent nucleoli, a finding that is compatible with Burkitt lymphoma. (f) Photomicrograph (original magnification, ⫻200; hematoxylin-eosin [H-E] stain) of a specimen obtained at core biopsy shows malignant cells
with monotomous round nuclei and fine powdery chromatine. Note also the extensive necrosis. (g) Photomicrograph (original magnification, ⫻200; immunohistochemical staining for CD 20) of a specimen obtained at
core biopsy shows strong positivity (brown areas), a finding that indicates a B-cell phenotype. Immunostaining
for CD 45 (lymphocytic proliferation) and CD 10 was also positive, findings that helped confirm the diagnosis
of Burkitt lymphoma.
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Figure 3. Recurrent B-cell lymphoma in a 19-year-old man. (a) Contrast-enhanced CT scan obtained at the time
of initial diagnosis shows a well-defined expansile mass (arrow) in the medial portion of the left kidney. (b) Contrastenhanced CT scan obtained at the same time as a shows that a portion of the tumor (arrow) has a poorly defined
margin and infiltrates the renal parenchyma. (c) FDG PET (left) and CT (right) scans obtained 9 months after treatment show multiple foci of intense activity (arrows) in the right kidney. (Fig 3c courtesy of Richard Wahl, MD, Johns
Hopkins Medical Institutions, Baltimore, Md.)
Positron Emission Tomography
Positron emission tomography (PET) has
emerged as a very useful technique for the staging of lymphomas and the detection of recurrent
disease. Because it helps detect increased metabolic activity within lymphomatous deposits,
fluorodeoxyglucose (FDG) PET is more sensitive
and specific than conventional anatomic imaging
in detecting additional small tumor deposits (29).
Combined PET-CT is emerging as a powerful
tool that demonstrates the metabolic activity of
tumors as well as anatomic details, a combination
that allows precise localization and potential earlier detection of additional tumor foci (Fig 3)
(30).
Radiologic-Pathologic Correlation
Renal lymphoma has a variety of imaging appearances depending on the pattern of tumor proliferation at histologic analysis (31).
Malignant lymphocytes reach the renal parenchyma by means of hematogenous spread and
proliferate within the interstitium, using the
nephrons, collecting tubules, and blood vessels as
a “scaffolding” for further growth. Alternatively,
some tumors spread by means of contiguous extension from the retroperitoneum, penetrating the
Teaching
Point
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Figure 4. Large B-cell lymphoma in a 41-year-old HIV-positive man. (a) Unenhanced CT scan of the midabdomen shows a soft-tissue mass (arrowhead) in the region of the great vessels, a finding that is suspicious for
retroperitoneal adenopathy. The kidneys do not demonstrate any abnormality in contour. (b) Contrast-enhanced CT scan of the midabdomen shows bilateral soft-tissue renal masses (arrows). Note that these masses
do not deform the contour of the kidneys. The paraaortic retroperitoneal adenopathy (arrowhead) is much
more clearly depicted than in a.
renal capsule. Once the tumor reaches the kidneys, its radiologic appearance is determined by
its predominant proliferation mechanism. If the
tumor follows an infiltrative growth pattern and
malignant cells proliferate along the scaffolding of
the normal interstitial tissue, the kidneys enlarge
but their normal shape is preserved (32,33). The
lesions have ill-defined borders and may be quite
subtle (34). In many cases, however, malignant
lymphocytes proliferate focally, destroy the adjacent renal parenchyma, and form single or (more
commonly) bilateral expansile lesions with welldefined margins. Small masses may coalesce and
grow, thereby distorting the renal contour (31). A
combination pattern is not unusual (Fig 3).
Imaging Patterns
Teaching
Point
Renal lymphoma has a wide variety of manifestations, including multiple lesions, a solitary lesion,
direct extension from retroperitoneal adenopathy,
preferential involvement of the perinephric space,
and diffuse infiltration of one or both kidneys.
The renal sinus and collecting system are less frequently affected, except for obstruction caused by
retroperitoneal adenopathy. In a large autopsy
series of 696 patients with lymphoma, Richmond
et al (1) observed multiple renal masses in 61% of
cases. A solitary renal nodule and direct invasion
from retroperitoneal adenopathy were equally
common, being found in 11 kidneys each.
Multiple Lesions
The most common imaging appearance of renal
lymphoma is that of multiple parenchymal masses
of variable size, typically 1– 4.5 cm in diameter.
This pattern is seen in 50%– 60% of cases. The
lesions are most often bilateral but may also affect
only one kidney (3–5,7,26).
At unenhanced CT, these masses appear as
soft-tissue lesions with slightly higher attenuation
than that of the surrounding parenchyma. Calcifications within the lesions are rare. Nephrographic
phase contrast-enhanced CT is essential because
many lesions are small and affect the medullary
portion of the kidneys, with relatively little cortical deformity (22). Lymphomatous deposits enhance less than the normal renal tissue and appear as relatively homogeneous masses with lower
attenuation than that of the surrounding cortex.
Large lesions tend to be more heterogeneous.
The presence of retroperitoneal adenopathy is an
additional clue to the diagnosis (Fig 4).
Teaching
Point
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Figure 5. B-cell lymphoma in a 33-year-old man who presented with progressive weakness of
the upper extremities. (a) Transverse US image of the right kidney shows multiple hypoechoic
soft-tissue masses (arrows) in the parenchyma. Note that the normal shape of the kidney is preserved. Similar hypoechoic masses were seen in the left kidney. The patient had concomitant central nervous system involvement. (b) Sagittal color Doppler US image of the right kidney shows
displacement of the renal vessels by the masses.
Figure 6. Multifocal renal cell carcinoma in a 68year-old man with right upper quadrant pain. (a) Arterial phase contrast-enhanced CT scan of the kidneys
shows bilateral hypervascular, heterogeneous masses
(arrows). (b) Excretory phase contrast-enhanced CT
scan of the kidneys also shows the masses (arrows). The
left renal mass is centrally located and involves the collecting system. (c) Photomicrograph (original magnification, ⫻200; H-E stain) of a specimen obtained at core
biopsy of the right renal mass shows a clear cell tumor
with prominent capillary proliferation. This finding is
compatible with the diagnosis of renal cell carcinoma.
Biopsy of the left renal mass was also performed and
demonstrated renal cell carcinoma. The patient was
treated with partial right nephrectomy and total left
nephrectomy.
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lesions are usually clinically silent and detected
incidentally in patients with disseminated tumor.
In the rare case in which there is no relevant clinical history, imaging-guided biopsy is indicated.
Acute pyelonephritis, septic emboli to the kidneys, renal infarcts, and abscesses should also
be considered in the differential diagnosis (36).
Thickening of perirenal fascial planes and infiltration of perinephric fat can be present in both inflammatory processes and lymphoma. Multiple
synchronous renal cell carcinomas are differentiated on the basis of their hypervascular enhancement pattern (Fig 6).
Figure 7. Large B-cell lymphoma in a 72-year-old
man with a history of prostate cancer. Contrast-enhanced CT scan of the kidneys shows a well-defined
expansile mass (arrow) in the left kidney. No other
solid renal masses are seen, but the right psoas muscle
(arrowhead) is enlarged. The diagnosis was established
with US-guided percutaneous biopsy of the renal mass.
Few reports have described the MR imaging
appearance of renal lymphomas. Tumors have
lower signal intensity than does normal cortex
with T1-weighted sequences and are relatively
iso- or hypointense with T2-weighted sequences.
They enhance less than the renal parenchyma
following intravenous administration of gadolinium-based contrast material (Fig 2) (24).
At US, lymphomatous masses are typically
hypoechoic and homogeneous. Their US appearance reflects the underlying homogeneity of lymphoma deposits, which offer very few tissue interfaces to the insonating beam (6,23,26). Color or
power Doppler US shows displacement of normal
renal vessels with little vascularity within the lesions (Fig 5).
Metastatic disease to the kidneys may mimic
renal lymphoma. Large autopsy series show that
lung cancer is the most common primary malignancy to spread to the kidneys, followed by breast
cancer, gastric cancer, and melanoma (35). These
Solitary Lesion
Renal lymphoma manifests as a solitary mass in
10%–25% of patients (4,5,31). At contrast-enhanced CT, the mass characteristically demonstrates little enhancement following intravenous
contrast material administration (Fig 7). This
feature is helpful in differentiating renal lymphoma from conventional renal cell carcinoma,
which usually enhances in the arterial phase. At
US, renal cell carcinoma tends to appear more
echogenic than lymphoma (Fig 8). In addition,
the presence of associated thrombus in the renal
vein or inferior vena cava is highly unusual in
lymphoma. However, some primary renal tumors,
such as the papillar and chromophobe variants of
renal cell carcinoma, do not exhibit this classic
enhancement (Fig 8). In such cases, percutaneous biopsy is required for definitive diagnosis to
exclude an atypical renal cell carcinoma or a solitary metastasis.
A cystic appearance is also highly unusual in
renal lymphoma. Of the 28 cystic Bosniak III lesions reviewed in one study, only one proved to
be lymphoma at biopsy (37), and rare cases of
lymphoma infiltrating a cyst wall have also been
reported (38). Some lesions may contain large
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Figure 8. Papillary renal cell carcinoma mimicking lymphoma in a 57-year-old woman with a history of liver transplantation and a new renal mass. (a) Corticomedullary phase contrast-enhanced CT scan shows a solitary hypovascular mass (arrow) in the left kidney, a finding that is atypical for renal cell carcinoma. (b) On an early excretory
phase contrast-enhanced CT scan, the mass (arrow) remains hypoattenuating relative to the renal parenchyma, despite minimal heterogeneous enhancement within the mass. (c) On a sagittal US image of the left kidney obtained at
the time of biopsy, the mass (cursors) is mildly echogenic. This finding would be atypical for lymphoma, which is
generally hypoechoic. (d) Photomicrograph (original magnification, ⫻50; Diff-Quik stain) of a specimen obtained at
fine-needle aspiration biopsy shows hypercellularity with numerous tissue fragments displaying a prominent papillary
architecture (arrow), a finding that is compatible with a well-differentiated papillary renal cell carcinoma. The patient
underwent left nephrectomy.
low-attenuation areas, perhaps related to necrosis, particularly during chemotherapy (Fig 9).
Lymphoma can appear markedly hypoechoic at
US and even exhibit some degree of enhanced
through transmission, thereby mimicking a cystic
mass (Fig 9c).
Direct Extension from
Retroperitoneal Adenopathy
Contiguous extension to the kidneys or perinephric space from large retroperitoneal masses is the
second most common pattern (25%–30% of
cases) (3). These patients usually have widespread disease with bulky tumors, and many are
immunocompromised. At imaging, large retroperitoneal masses are seen invading or displacing
the adjacent kidney (Fig 10). Hydronephrosis
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Figure 9. Recurrent large B-cell lymphoma in a 61year-old man who had been treated with high-dose chemotherapy. (a) Venous phase contrast-enhanced CT scan
shows a low-attenuation mass (arrow) in the left kidney.
The lesion has thick walls, and there is stranding as well as
subtle nodular thickening in the perinephric space (arrowhead). (b) Contrast-enhanced CT scan of the mediastinum shows a large, subcarinal nodal mass (arrow).
(c) Transverse US image of the left kidney shows a complex, partially cystic renal mass (arrow). Note the thick
wall, multiple septa, and minimal through transmission
(arrowheads).
Figure 10. Low-grade B-cell lymphoma in a 60-year-old man. The patient underwent abdominal CT for necrotizing pancreatitis. (a) Venous phase contrast-enhanced CT scan shows a large soft-tissue mass (arrow) infiltrating the
retroperitoneum, encasing the left renal vessels, and extending into the perinephric space. Note the fluid collection
(arrowhead) in the pancreatic bed, a finding that is consistent with the patient’s history of pancreatitis. (b) Excretory
phase contrast-enhanced CT scan shows a pararenal mass (arrow) with soft-tissue attenuation. Note also the absence
of hydronephrosis. Although pancreatitis commonly affects the perirenal and pararenal spaces, the soft-tissue attenuation of the mass in this case led to the correct diagnosis of lymphoma. The diagnosis was confirmed with US-guided
biopsy.
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Figure 11. Burkitt lymphoma affecting the retroperitoneal nodes, adrenal glands, and kidneys in a 46-yearold man. (a) Sagittal US image shows a large hypoechoic mass (arrows) displacing and infiltrating the left kidney. Note also the mild left hydronephrosis (arrowheads). (b) Transverse color Doppler US image shows the
mass (arrows) encasing the left renal artery and vein. Several small, subtle hypoechoic masses were seen in the
right kidney. A right adrenal mass was also seen. AO ⫽ abdominal aorta.
caused by entrapment of the ureters is common;
however, occlusion or thrombosis of major renal
arteries and veins is rare despite extensive tumor
encasement (Fig 11).
Perinephric Disease
Although perirenal spread from retroperitoneal or
renal lymphoma is not uncommon, isolated perinephric lymphoma is unusual (⬍10% of cases)
(3,4). CT scans acquired after the administration
of intravenous contrast material are invaluable for
demonstrating a rind of homogeneous perineph-
ric soft tissue compressing the normal parenchyma without causing significant impairment of
renal function (Fig 12). In less dramatic cases,
findings are limited to thickening of the Gerota
fascia or plaques and nodules in the perirenal
space (Fig 13) (3,4,36). At US, hypoechoic tissue
of variable thickness is seen surrounding the kidney (Fig 12c) (39).
The differential diagnosis includes sarcoma
arising from the renal capsule and metastases to
the perinephric space, as well as benign conditions such as perinephric hematoma, retroperitoneal fibrosis, amyloidosis, and extramedullary
hematopoiesis (Fig 14) (36,40).
Figure 12. Perinephric disease in a 66-year-old man with an incidental finding of a left renal mass. (a) Unenhanced CT scan shows marked enlargement of the left kidney (arrows). Left paraaortic lymph nodes (arrowhead) are
seen encasing the left renal vein. (b) Corticomedullary phase contrast-enhanced CT scan shows a large hypovascular
mass (arrows) located primarily in the perinephric space. The mass appears to invade the left renal parenchyma. Note
that there is no significant enhancement delay in the left renal parenchyma relative to the right kidney. Arrowhead
indicates paraaortic lymph nodes encasing the left renal vein. (c) Sagittal US image obtained at the time of biopsy
shows a hypoechoic mass (arrows) surrounding and partially invading the left kidney. (d) Photomicrograph (original
magnification, ⫻100; H-E stain) of a specimen obtained at core biopsy shows numerous lymphocytes with focal
nuclear crush artifact infiltrating dense fibrous tissue (arrow). (e) Photomicrograph (original magnification, ⫻200;
immunohistochemical staining) of a specimen obtained at core biopsy shows strong reactivity with CD 20, a finding
that indicates a B-cell phenotype.
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Figure 13. B-cell lymphoma in a 62-year-old man with a history of follicular lymphoma. Routine follow-up CT
was performed. (a) Portal venous phase contrast-enhanced CT scan shows a mildly enhancing mass (arrow) in the
right anterior pararenal space. The mass represented a new finding. (b) Portal venous phase contrast-enhanced CT
scan shows stranding in the mesenteric fat (arrows), a finding that suggests a “misty mesentery.” This finding was
also new. US-guided biopsy of the perirenal mass demonstrated aggressive B-cell lymphoma.
Figure 14. Perinephric hematoma in a 65-year-old
man with a history of idiopathic thrombocytopenic purpura and newly diagnosed low-grade lymphoma. Contrast-enhanced CT scan shows a high-attenuation fluid
collection (arrows) in the right perinephric space. USguided aspiration biopsy yielded clotted blood.
Nephromegaly
Nephromegaly without distortion of the normal
shape of the kidneys results from diffuse infiltration of the renal interstitium by malignant lymphocytes. This appearance is more common
in Burkitt lymphoma, either disseminated or limited to the kidneys (primary renal lymphoma)
(8,17,18,20). Acute renal failure caused by destruction of the normal renal architecture may
Figure 15. Primary renal lymphoma in a 41-year-old
HIV-positive man who presented with renal failure.
Nephrographic phase contrast-enhanced CT scan of
the kidneys shows bilateral renal enlargement. Heterogeneously decreased enhancement of the renal parenchyma is also seen. The diagnosis of Burkitt-like lymphoma was established with renal biopsy.
lead the patient to seek medical attention if both
kidneys are extensively infiltrated.
Although the diagnosis can be suspected in the
presence of global renal enlargement, administration of intravenous contrast material is critical for
demonstrating heterogeneous enhancement of the
kidneys, loss of the normal differential enhancement between the cortex and the medulla in the
corticomedullary phase, and infiltration of the
renal sinus fat (Fig 15). Alternatively, the renal
parenchyma is replaced by poorly marginated
low-attenuation lesions. The collecting system is
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Figure 16. Transitional cell carcinoma infiltrating the right kidney in a 44-year-old man with right flank pain.
(a) Corticomedullary phase contrast-enhanced CT scan shows a mass (arrow) infiltrating the right kidney. Note the
delayed right renal enhancement and paracaval adenopathy (arrowhead). (b) Sagittal US image of the left kidney
shows a large heterogeneous mass (arrows) infiltrating the renal parenchyma and sinus fat at the upper pole. Note
also the absence of hydronephrosis. (c) Photomicrograph (original magnification, ⫻400; Papanicolaou stain) of a
specimen obtained at fine-needle aspiration biopsy shows a malignant tumor with pleomorphic cells and large nuclei
with macronucleoli (arrow). The individual cell necrosis indicates a high-grade epithelial tumor. (d) Photomicrograph (original magnification, ⫻200; immunohistochemical staining) of a specimen obtained at core biopsy shows
strong reactivity with cytokeratin 7 (brown areas). There was also reactivity with thrombomodulin, a finding that
helped confirm the diagnosis of urothelial carcinoma.
often encased and stretched rather than displaced. Occasionally, lymphoma infiltrates and
destroys the renal parenchyma extensively and
manifests as a large, nonfunctioning kidney
(32,33).
The US manifestations of infiltrative renal
lymphoma are often quite subtle and include
globular enlargement of the kidneys with heterogeneous echotexture of the parenchyma and loss
of the normal echogenic appearance of the renal
sinus fat (Fig 3) (33).
In some cases, the infiltrative process is unilateral or asymmetric. Diffuse infiltration of the
kidney can also be caused by transitional cell
carcinoma (Fig 16), collecting duct or medullary
carcinoma of the kidneys, or severe pyelonephritis (33).
Renal Sinus Involvement
Lymphoma can preferentially affect the renal sinus, although this is an uncommon occurrence.
At CT, the normal renal sinus is replaced by a
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1166
Figure 17. B-cell lymphoma in a 70-year-old woman.
(a) Contrast-enhanced CT scan of the midabdomen
shows a homogeneous soft-tissue mass (arrows) in the left
renal sinus. Note the lack of significant hydronephrosis
and the presence of mesenteric and retroperitoneal adenopathy (arrowheads) as well as splenomegaly. (b) Sagittal US image of the left kidney shows a poorly defined infiltrating mass (arrows) in the region of the renal pelvis, a
finding that helps confirm the absence of hydronephrosis.
(c) On a color Doppler US image, the kidney is well vascularized and the mass (arrows) is hypovascular. The diagnosis was established with US-guided biopsy of the mass.
homogeneous soft-tissue mass (Figs 17, 18) (41).
Vascular encasement is common; because of the
pliable nature of the tumor, however, the resulting hydronephrosis is often mild.
At US, renal sinus lymphoma appears as a hypoechoic mass infiltrating the renal sinus. This
type of lymphoma may be difficult to differentiate
from heterogeneous renal sinus fat, since both
conditions tend to have poorly defined borders
and traversing hilar vessels (Fig 19) (42).
Transitional cell carcinoma is usually associated with a greater degree of obstruction of the
collecting system. Castleman disease rarely occurs in the renal hilum but cannot be identified
without histologic sampling (43).
Diagnostic Role of
Imaging-guided Renal Biopsy
Several published studies have confirmed the usefulness and safety of imaging-guided percutaneous biopsy in the diagnosis of renal masses (44 –
46). Generally accepted indications include the
presence of a solid renal mass in a patient with
known malignancy, an indeterminate cystic lesion, and suspected renal cell carcinoma that is
either found to be unresectable or seen in a poor
surgical candidate (45,46). Whenever renal lesions exhibit imaging characteristics suggesting
renal lymphoma, imaging-guided percutaneous
Figure 18. Large B-cell lymphoma in a 52-year-old
man with a history of chronic lymphocytic leukemia.
Contrast-enhanced CT scan shows bulky retroperitoneal adenopathy (black arrows). A soft-tissue mass
(white arrow) is seen in the right renal sinus fat and the
perinephric space. Note the delayed enhancement of
the right kidney.
biopsy should be recommended. This technique
has a critical impact on case management in that
it makes potentially unnecessary nephrectomy
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rial is contraindicated. Although the role of US is
limited to evaluating disease spread to the reproductive organs, US is routinely used as a guidance
modality for percutaneous biopsy.
References
Figure 19. Recurrent Hodgkin lymphoma manifesting as a right renal hilar mass in a 29-year-old man.
Sagittal US image of the right kidney shows an ill-defined hypoechoic mass (arrow) infiltrating the renal
sinus fat. The diagnosis was confirmed with US-guided
percutaneous fine-needle aspiration biopsy and core
biopsy.
avoidable. Both CT- and US-guided procedures
have a reported accuracy of 89%–92% (47– 49).
We strongly favor US guidance because it offers
real-time needle guidance and does not involve
radiation. Core biopsy as well as flow cytometric
and immunohistochemical studies are essential in
confirming the diagnosis and classifying the tumor prior to therapy, with satisfactory specimens
being reported in 69%– 82% of cases. The diagnostic yield is higher in cases of non-Hodgkin
lymphoma than in cases of Hodgkin disease (47–
49). Immunohistochemical stains are routinely
used employing conventional methodology and
include leukocyte common antigen, CD20 (B-cell
marker), CD3 (T-cell marker), kappa and lambda
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CD33, CD22, CD19, CD20, kappa and lambda
light chains, CD5, CD3, and CD56. Additional
antibodies are used in cases of lymphoma with a
previously diagnosed unusual immunophenotype.
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for initial diagnosis, staging, and monitoring of
the disease. MR imaging is useful in selected
cases, particularly in patients in whom intravenous administration of iodinated contrast mate-
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This article meets the criteria for 1.0 credit hour in category 1 of the AMA Physician’s Recognition Award. To obtain
credit, see accompanying test at http://www.rsna.org/education/rg_cme.html.
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RG
Volume 26 • Volume 4 • July-August 2006
Sheth et al
Imaging of Renal Lymphoma: Patterns of Disease with
Pathologic Correlation
Sheila Sheth, MD, et al
RadioGraphics 2006; 26:1151–1168 ● Published online 10.1148/rg.264055125 ● Content Codes:
Page 1152
The genitourinary system is often affected by extranodal spread of lymphoma, being the second most
commonly affected anatomic entity next to the hematopoietic and reticuloendothelial organs (1).
Page 1154
Multi-detector row CT is the imaging modality of choice for the evaluation of patients with suspected
renal lymphoma.
Page 1156
Renal lymphoma has a variety of imaging appearances depending on the pattern of tumor
proliferation at histologic analysis (31).
Page 1157
Renal lymphoma has a wide variety of manifestations, including multiple lesions, a solitary lesion,
direct extension from retroperitoneal adenopathy, preferential involvement of the perinephric space,
and diffuse infiltration of one or both kidneys.
Page 1157
Lymphomatous deposits enhance less than the normal renal tissue and appear as relatively
homogeneous masses with lower attenuation than that of the surrounding cortex.