Diagnostic Ultrasound - Abdomen and Pelvis

Renal Cell Carcinoma
TERMINOLOGY
Abbreviations
• Renal cell carcinoma (RCC)
Synonyms
• Renal cell adenocarcinoma, hypernephroma
Definitions
• Malignant tumor arising from proximal tubular epithelium
IMAGING
General Features
• Best diagnostic clue
○ Hypervascular solid renal mass
○ Macroscopic fat practically excludes RCC
○ Extension into veins
• Location
○ Renal cortex
○ Tumors usually solitary but may be multifocal (6-25%) or
bilateral (~ 4%)
• Morphology
○ Usually solid mass; variants are cystic (< 5%)
• Subtypes include
○ Clear cell adenocarcinoma (60-70%)
○ Papillary (5-15%)
○ Chromophobe (5%)
○ Collecting duct (< 1%),unclassified (4%)
Ultrasonographic Findings
• Grayscale ultrasound
○ Variable appearance: Solid, cystic or complex
○ Hyperechoic (48%), isoechoic (42%), or hypoechoic (10%)
○ Small tumors are usually hyperechoic; simulate
angiomyolipoma (AML)
○ Large tumors tend to be hypoechoic, exophytic with
anechoic necrotic areas
○ Hypoechoic rim resembling "pseudocapsule"
○ Cystic variant: Unilocular or multilocular, fluid-debris
levels (hemorrhage and necrosis), thick and irregular wall
or septations, nodules
• Color Doppler
○ Discernible tumor vascularity; most prominent around
tumor periphery,< renal parenchyma
– Contrast-enhanced ultrasound can improve detection
of neovascularity
CT Findings
• NECT
○ Solid or complicated cystic mass, hyperdense, isodense,
or hypodense compared to renal tissue
○ Heterogeneous mass (hemorrhage and necrosis)
○ Calcifications have high positive predictive value for
malignancy when amorphous and in solid components
○ Intratumoral fat is extremely rare and associated with
osseous metaplasia
• CECT
○ Degree of enhancement most valuable in differentiating
RCC subtypes
○ Clear cell RCC: Hypervascular, heterogeneous, mixed
enhancement pattern with both enhancing soft tissue
components and areas of necrosis
– Enhances more than other subtypes
○ Papillary RCC: Hypovascular, typically homogeneous;
may be partly cystic
○ Cystic RCC variants: Uni-/multilocular cystic mass with
thick wall and nodular component, enhancing smooth or
nodular septa
○ RCC occasionally diffusely infiltrative or infiltrates
collecting system
○ Lucent rim (pseudocapsule)
○ Direct extension to renal vein (RV) (20-35%), inferior
vena cava (IVC) (4-10%), adjacent muscles, and viscera
MR Findings
• Isointense (60%) on T1WI and T2WI or hyperintense (40%)
on T2WI
• Hypointense band/rim on T1WI (25%) and T2WI (60%)
• T1WI C+: Enhances, usually less than renal tissue
Image-Guided Biopsy
• Increasing role in selecting patients for treatment or
surveillance based on subtype
• Performed in setting of widely metastatic disease or when
there is another malignancy
• Used to confirm diagnosis prior to ablative therapy, as up to
30% of small solid renal masses are benign
Imaging Recommendations
• Best imaging tool
○ RCC may be initially detected by US but CECT and MR are
primary tools for characterization and staging
○ In select patients, US may be used for screening and
follow-up depending on body habitus
○ MR/US preferred over CT for long-term surveillance
based on radiation concerns
• Protocol advice
○ Ultrasound may be useful in characterizing complex
cystic lesions, which are indeterminate or equivocal on
CECT or MR
– Use Doppler (color/power/pulsed) for detection of
internal vascularity
– Contrast-enhanced ultrasound sensitivity of 96% for
classifying complex cystic renal masses
DIFFERENTIAL DIAGNOSIS
Renal Angiomyolipoma
• Homogeneous, well-defined, noncalcified, echogenic
cortical mass with occasional posterior acoustic shadowing
• Characteristic macroscopic fat confirmed with CT or MR
• Both AML with minimal fat and RCC can contain
microscopic fat on chemical shift imaging; AML with
minimal fat usually hypointense on T2WI MR
Transitional Cell Carcinoma (TCC)
• Infiltrative tumor involving renal parenchyma may be
indistinct from infiltrative RCC
• Renal pelvic filling defect, irregular narrowing of collecting
system, hypovascular
Diagnoses: Urinary Tract
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