Renal Cell Carcinoma



Renal Cell Carcinoma


Todd M. Blodgett, MD

Alex Ryan, MD

Hesham Amr, MD









Graphic shows a typical appearance of a large renal cell carcinoma image with invasion of the renal vein and inferior vena cava image.






Coronal PET (A), axial CT (B) and fused PET/CT (C) show a relatively non-FDG-avid renal cell carcinoma image.


TERMINOLOGY


Abbreviations and Synonyms



  • Renal cell carcinoma (RCC), clear cell carcinoma, hypernephroma, renal cancer


Definitions



  • Carcinoma of renal tubular epithelium


IMAGING FINDINGS


General Features



  • Best diagnostic clue



    • Iso- or hypermetabolic renal mass ± lymphadenopathy, metastases on FDG PET


    • Presents most commonly as incidental solid tumor on imaging


    • Enhancing solitary mass on CT highly suspicious for RCC



      • Necrosis, hemorrhage, septae more likely in large masses


  • Location



    • Usually renal cortex


    • Often exophytic


    • Rarely bilateral (2%) or multicentric (more common in von Hippel-Lindau)


  • Size: Variable depending on time of diagnosis


  • Morphology



    • 10% calcified, often irregular


    • 2-5% cystic


Imaging Recommendations



  • Best imaging tool



    • Combination of CT, ultrasound



      • CECT often shows enhancing lesion; hyperdense benign cysts will not enhance


      • US indicated in patients with nonenhancing hyperdense renal lesions to differentiate cyst from mass


      • If contraindication to contrast, MR superior to CT


    • FDG PET and PET/CT not currently covered by Medicare, but may be helpful for staging and restaging


  • Protocol advice



    • For CT: Noncontrast and CECT, thin sections (2.5-5.0 mm), during both corticomedullary and nephrographic phases




      • For PET CT: If only single phase obtained, use later nephrographic phase of contrast enhancement


    • Corticomedullary phase (25-70 seconds post-injection)



      • Better visualization of renal vessels; evaluate for renal vein/IVC thrombosis or tumor extension


      • Limited detection of small renal lesions


      • Centrally located tumors commonly mistaken for normal hypoattenuating medulla


    • Nephrographic phase (80-180 seconds post-injection)



      • Best imaging of renal medulla masses


CT Findings



  • NECT



    • Solid-tissue-density mass, which distorts normal kidney contour and typically is in the 30-50 HU range


    • Can be hyperdense, isodense, or hypodense to surrounding normal kidney


    • Heterogeneous mass (hemorrhage and necrosis); high (acute hemorrhage) or low attenuation (chronic)



      • ± Calcifications (10% of cases); amorphous internal (most common), curvilinear (peripheral or central), dense or diffuse calcification


    • High density rim may separate mass from adjacent renal tissue (pseudocapsule)


    • Rarely contains small areas of fat (-50 to -150 HU)


    • Combination of fat and calcification suggests RCC, not renal angiomyolipoma


    • Cystic RCC



      • Uni- or multilocular cystic mass with a thick calcification of septa or tumor capsule


      • Septa may enhance on CECT


  • CECT



    • Hypervascular mass with enhancement (HU increase by > 20) compared to noncontrast



      • Enhancement often heterogeneous, particularly larger lesions


    • Tumor extension or thrombus in renal vein (23%), inferior vena cava (7%)


    • Local extension common



      • Nodal spread typically to para-aortic or aortocaval lymph nodes


    • Most common metastatic locations include lung, liver, bone, adrenal, and opposite kidney


    • Usually solid, and decreased attenuation suggestive of necrosis often present


    • Sometimes presents as predominantly cystic mass with thick septa and wall nodularity


    • Nephrographic phase is most sensitive for tumor detection, especially for masses smaller than 3 cm


    • Corticomedullary phase required for tumor extension into renal veins



      • Evaluation for hypervascular metastases


    • Helical CT improves diagnosis and eliminates respiratory misregistration


Nuclear Medicine Findings



  • FDG PET and PET/CT for RCC



    • Iso- or hypermetabolic renal mass ± lymphadenopathy, metastases


    • FDG uptake by primary RCC and metastases is somewhat variable; therefore, PET and PET/CT are more helpful when positive



      • Negative study may represent either a non-FDG-avid RCC or truly negative disease


    • Sensitivity 60%, specificity ˜ 100% for evaluating primary RCC


    • Excretory FDG in collecting system can mask small RCCs adjacent to collecting system


    • 80-100% specific for bony metastases


DIFFERENTIAL DIAGNOSIS


Angiomyolipoma (AML)



  • Fat attenuation (-30 to -150 HU) fairly specific for this neoplasm


  • Low FDG uptake


  • Reliably distinguished from malignancy by CT characteristics



Renal Oncocytoma



  • Central scar on CT/MR and spoke-wheel pattern of vessels on angiograms suggest oncocytoma; not entirely specific


  • Cannot confidently differentiate from RCC by PET


Hemorrhagic Renal Cyst



  • > Water attenuation on CT (˜ 30-70 HU)


  • Should not enhance when comparing noncontrast and CE series


Transitional Cell Carcinoma (TCC)



  • Renal pelvis filling defect, narrowing


  • Urothelial thickening or involvement


  • Rare parenchymal TCC indistinguishable from RCC


Lymphoma



  • Typically more diffusely infiltrative than discrete mass


Renal Infection or Abscess



  • Focal nephritis can appear mass-like



    • Short term follow-up helpful


  • Clinical history and urine analysis often helpful


Metastatic Disease



  • History essential


  • Common primary cancers include lung, breast, colon, melanoma, pancreatic


  • Typically only hypervascular metastases mistaken for RCC


PATHOLOGY


General Features



  • General path comments



    • Staging



      • Stage I: Solid mass ≤ 7 cm, confined to kidney


      • Stage II: > 7 cm but still organ confined; spread to perinephric fat


      • Stage III: Invasion of renal vein or vena cava, involvement of ipsilateral adrenal gland &/or perinephric fat, or spread to one local lymph node


      • Stage IV: Invasion of adjacent organs, more than one local node, or distant metastases


  • Genetics: Associated with von Hippel-Lindau syndrome (autosomal dominant)


  • Etiology



    • Arise from tubular epithelium


    • Bilateral lesions associated with von Hippel-Lindau syndrome, tuberous sclerosis, chronic dialysis


    • Other risk factors: Smoking, chemical exposure (diethylstilbestrol and fluoroacetamide)


  • Epidemiology



    • Approximately 2% of adult malignancies (30,000/year in USA)


    • Undiagnosed small RCCs found at autopsy even more frequently


Gross Pathologic & Surgical Features



  • Solid to cystic components with necrosis, hemorrhage, and rarely fat


Microscopic Features



  • 70% clear cell, 13% papillary, 7% granular, 10% other


CLINICAL ISSUES


Presentation



  • Most common signs/symptoms



    • Usually a combination of hematuria (50%), flank pain (40%), &/or flank mass (35%)


    • Nearly half of RCCs discovered incidentally


  • Other signs/symptoms



    • Fever, nausea, weight loss


    • Rarely, humoral factors such as erythropoietin, renin, parathyroid hormone, or prolactin may cause symptoms


Demographics



  • Age: Generally 50-70 years, with wide distribution


  • Gender: M > F, 2:1

Sep 22, 2016 | Posted by in MAGNETIC RESONANCE IMAGING | Comments Off on Renal Cell Carcinoma
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