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Key points

Transitional cell carcinoma (TCC) of the renal pelvis

  • Less common than renal cell carcinoma
  • Difficult to detect on imaging when small and/or early stage
  • Also known as urothelial cell carcinoma of the renal pelvis

Pathophysiology

  • Transitional cell carcinomas comprise approximately 85% of all uroepithelial tumors of the renal pelvis. Two main morphologies:
    • Nonpapillary:
      • Sessile or nodular mass
      • Typically early mucosal invasion and high grade initially
    • Papillary: 
      • Multiple frondlike papillary projections
      • Typically low-grade mucosal invasion seen in later stages
      • 85% of TCCs
  • Squamous cell carcinomas make up the remaining 10%-15%; rarely, adenocarcinoma

Epidemiology

  • Represent approximately 5%-10% of all renal tumors
  • TCCs in the renal pelvis are rare: bladder (50x more common) >> renal pelvis >> ureter (2x-3x less common)
  • Difference in affected sites of urothelial tract likely due to differing surface areas and urinary stasis, i.e., exposure of urothelium to carcinogens
  • More common in men ages 60-70 years
  • Typically low grade, with good overall prognosis of 90% five-year survival

Clinical presentation

  • Microscopic or macroscopic hematuria
  • Possibly hydronephrosis and/or flank pain if at the pelviureteric junction or if associated with intravascular thrombus
  • Possibly asymptomatic until late stage of disease (metastatic) resulting in focal symptoms from metastases (e.g., pathologic fracture in bone metastasis) or constitutional symptoms (e.g., weight loss)

Imaging features

  • CT abdomen/pelvis and CT urogram:
    • Typically soft-tissue attenuation (8-30 HU) with mild contrast enhancement (18-55 HU), significantly less enhancing compared to renal parenchyma or renal cell carcinomas, although not always the case
    • Centered on renal pelvis
    • May be small filling defects or large masses that obliterate renal sinus fat (TCC is one presentation of the so-called "faceless kidney") but otherwise preserve the normal renal contour while infiltrating the renal pelvis
    • May have scattered areas of hypoattenuation internally representing areas of necrosis
    • May have scattered small calcifications on the papillary projection surface(s)
    • Stipple sign: dappled appearance when contrast fills the spaces between the papillary projections
    • Oncocalyx: distended calyx due to tumor
    • Phantom calyx: prevented from contrast filling due to space-occupying mass
  • Ultrasound:
    • Appear as solid, hypoechoic masses in the renal pelvis or in a dilated calyx
    • Masses may demonstrate peripheral or internal vascularity on color Doppler, but this may be technically dependent
  • MRI:
    • Isointense to renal parenchyma on both T1- and T2-weighted images
    • Mild relative enhancement to normal renal parenchyma

Treatment

  • Early: surgery, e.g., nephroureterectomy
    • Low-stage: renal-sparing surgery (local excision)
    • In some cases, bacille Calmette-Guerin (BCG) or mitomycin C has been instilled into the upper tract as an alternative to surgery
  • High rate of recurrence due to field effect on urothelium
  • Metastases are most common to liver, bone, and lung

References

  1. Dyer RB, Chen MY, Zagoria RJ. Classic signs in uroradiology. Radiographics. 2004;24 Suppl 1:S247-S280.
  2. Leder RA, Dunnick NR. Transitional cell carcinoma of the pelvicalices and ureter. AJR Am J Roentgenol. 1990;155(4):713-722.
  3. Vikram R, Sandler CM, Ng CS. Imaging and staging of transitional cell carcinoma: Part 2, upper urinary tract. AJR Am J Roentgenol. 2009;192(6):1488-1493. 
Our appreciation is extended to Drs. Hena Ahmed Cheema and Joanie Garratt, University of Pennsylvania Department of Radiology, for contributing this case.