Diagnostic Ultrasound - Abdomen and Pelvis

Renal Lymphoma
TERMINOLOGY
Abbreviations
• Primary renal lymphoma (PRL); secondary renal lymphoma
(SRL)
Definitions
• Lymphoma: Malignant tumor of lymphocytes
• Primary: Involvement of kidneys without evidence of other
organ or nodal involvement
○ Extremely rare; < 1% of extranodal lymphoma
• Secondary: Dissemination of extrarenal lymphoma by
hematogenous spread (90%) or direct extension via
retroperitoneal lymphatic channels
○ Non-Hodgkin lymphoma >> Hodgkin disease
IMAGING
General Features
• Morphology
○ Multiple hypoenhancing/hypoechoic masses (50-60%)
○ Direct extension from retroperitoneal adenopathy (25-
30%), associated hydronephrosis
○ Solitary hypoenhancing/hypoechoic mass (10-25%)
○ Bilateral renal enlargement (nephromegaly) (20%)
– More common in Burkitt lymphoma
○ Perinephric disease (< 10%); rind of homogeneous
perinephric soft tissue
– May be limited to thickening of Gerota fascia or
plaques and nodules in perirenal space
○ Renal sinus predominant: Uncommon, no vascular
invasion, milder hydronephrosis
Ultrasonographic Findings
• Grayscale ultrasound
○ Typically hypoechoic and homogeneous mass
○ Homogeneity of lymphoma results in few tissue
interfaces to insonating beam; there may even be
posterior acoustic enhancement
○ Solitary or multiple masses
– Small lesions may be confused with medullary
pyramids, renal cysts, or abscesses
○ Direct invasion: Hypoechoic mass extending from
retroperitoneum or perirenal space into renal
parenchyma or sinus
○ Nephromegaly: Globular enlargement with
heterogeneous echotexture and loss of normal
echogenic appearance of renal sinus fat
– Diffuse uniform increase in echogenicity may simulate
renal parenchymal disease
○ Perirenal lymphoma: Hypoechoic soft tissue of variable
thickness surrounding kidney
• Color Doppler
○ Displacement of normal renal cortical vessels with little
vascularity within lesions
○ Soft tissue surrounding renal hilar vessels or vena cava
without significant compromise
CT Findings
• Mildly hyperdense to normal kidney on unenhanced CT
• Hypovascular mass, unlike clear cell renal cell carcinoma
(RCC)
○ Note hypovascular subtypes of RCC, such as papillary and
chromophobe
• Despite large infiltrative retroperitoneal and perinephric
space masses, vena cava and renal vein are rarely invaded,
unlike RCC
• Nephromegaly with diffuse infiltration and heterogeneous
enhancement
• Difficult to differentiate from transitional cell carcinoma
(TCC) when epicenter of disease is in renal sinus
• Splenomegaly or lymphadenopathy at other sites in SRL
• Extranodal involvement of gastrointestinal tract, brain,
liver, and bone marrow
• Calcification and cystic change are rare
MR Findings
• Low to intermediate signal on both T1 and T2
• Heterogeneous high signal may be seen on T2WI
• May show restricted diffusion
• T1 C+: Heterogenous enhancement, less than that of
cortex
• Ideal for detecting synchronous osseous disease
Image-Guided Biopsy
• Important role to differentiate from other solid renal
masses and determine medical or surgical management
• US is ideal for guidance, but CT may be needed for deeper
lesions or lesions not visible on US
• Fine-needle aspiration supplemented by core biopsies: High
sensitivity and specificity
○ Immunochemistry, flow cytometry, and histopathology
drive specific therapies
• Renal mass biopsy not necessary in widespread lymphoma
unless renal mass is atypical or patient has 2nd malignancy
Nuclear Medicine Findings
• PET/CT
○ Important role in evaluation of both nodal and
extranodal lymphoma
○ Used for initial staging, evaluation of treatment
response, and detection of recurrence in some subtypes
of lymphoma
○ More sensitive than conventional anatomic imaging
○ 18F-FDG uptake much higher on average in renal
lymphoma (SUV mean 6.37) compared to RCC (SUV
mean 2.58)
Imaging Recommendations
• Best imaging tool
○ CECT is modality of choice for initial diagnosis and
staging of renal lymphoma
– Combined with 18F-FDG PET for initial staging,
assessment of response and detection of recurrence
○ MR is alternative in patients with impaired renal function;
avoids radiation exposure
DIFFERENTIAL DIAGNOSIS
Renal Cell Carcinoma
• Round or oval cortical solid or cystic mass ±central necrosis
• Typically hypervascular, however, some subtypes are
hypovascular
• Propensity to vascular invasion
Diagnoses: Urinary Tract
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