A 42-Year-Old Office Assistant With Chronic Leg and Back Pain

John G. Christensen, Jr, MD


March 05, 2021

RCC subtypes include clear cell (roughly 75%), papillary, chromophobe, collecting duct, and unclassified.[1] The papillary and chromophobe subtypes may portend better survival. The Fuhrman cellular grade of clear cell carcinoma is an independent predictor of survival. Sarcomatoid features can be found in any subtype and are associated with a worse prognosis. Oncocytoma, which may be associated with a central star-shaped density on CT scanning, does not metastasize and is considered a benign renal mass.

The presence of fat in a renal mass on CT or MRI images is pathognomonic of benign angiomyolipoma. Otherwise, solid renal masses should be considered likely malignant (≥80%) and possibly aggressive (≥20%) and treated as such.

The TNM staging for RCC is as follows[3,4]:

  • T1—Tumor ≤7 cm, limited to kidney

  • T1a—Tumor ≤4 cm

  • T1b—Tumor >4 cm and ≤7 cm

  • T2—Tumor >7 cm but limited to kidney

  • T3—Tumor involves renal vein, inferior vena cava (IVC), or perirenal fat but contained within Gerota fascia

  • T4—Tumor invades beyond Gerota fascia

American Joint Committee on Cancer staging is as follows[3,4]:

  • Stage I—T1, N0M0

  • Stage II—T2, N0M0

  • Stage III—T3, N0M0 or T1-3, N1M0

  • Stage IV—T4, N0-1M0; any T with M1

Tumor size is a strong predictor of survival. The 5-year disease-specific survival by T stage for RCC is as follows[3]:

  • T1—95%

  • T2—88%

  • T3—59%

  • T4—20%

The Fuhrman Nuclear Grading System is an independent predictor of survival. In patients with T1 disease, the 5-year cancer-specific survival rates after surgery are as follows[5]:

  • Fuhrman Grade 1—91%

  • Fuhrman Grade 2—83%

  • Fuhrman Grade 3—60%

  • Fuhrman Grade 4—0%

The objectives of imaging a renal mass are to rule out benign angiomyolipoma (any fat density seen), to evaluate for locally invasive features, to study the involved anatomy (for surgical planning), and to determine the status of the uninvolved kidney.[3]

Contrast-enhanced CT scanning is the imaging procedure of choice for diagnosis and staging of renal masses when renal function is adequate. Typically, this is a CT scan of the abdomen and pelvis without and then with contrast; this may include a delayed urogram phase.[1,2,3] Contrast-enhanced MRI is an optional imaging modality for initial evaluation. MRI is also recommended if renal vein or IVC involvement is in question. Urinary calculi may not show up on MRI.

Renal ultrasonography can be useful in evaluating cystic masses if CT imaging is inconclusive; however, ultrasonography may miss isodense renal tumors or transitional cell tumors of the renal collecting system.[3] Angiomyolipomas are suspected based on the high echogenicity of fat; however, a CT scan is more definitive.

Intravenous pyelography is inadequate to evaluate a renal mass due to low sensitivity and specificity.[3] Bone scanning is not routinely performed unless bone pain, elevated alkaline phosphatase, or other suspicion of bony metastases is present. The role of PET scanning in RCC has yet to be determined.[4]

Brain MRI or CT scanning can be performed if clinical signs or symptoms are suspicious for brain metastases.[4] Chest imaging (radiography or CT scanning) should be routinely included in the workup of a solid renal mass.


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