Papillary renal cell carcinoma (PRCC) is a distinct subtype of renal cell carcinoma (RCC). It represents approximately 8-15% of all RCC. This tumor is often associated with chromosomal abnormalities. There are at least two types of PRCC. Type 1 is found in hereditary PRCC and is associated with a good long-term prognosis. Type 2 is found in hereditary leiomyoma RCC syndrome and is a more aggressive form of cancer than type 1 [1, 2,3,4,5,6]. PRCC are villous tumors, with vascularized stalks. Despite this, the tumors are hypovascular in appearance . There is an increased risk of bladder and prostate cancer in this disease. Multifocality is also more often encountered in these patients . There are no specific clinical signs in PRCC. Flank pain, hematuria and flank mass are encountered in advanced disease [1,2]. Our patient presented only right flank pain.
Imaging is crucial in the detection, characterization and staging of PRCC. Ultrasonography provides accurate anatomic information on extrarenal extension of the tumor, adrenal or lymph node involvement, and invasion of neighboring viscera. US can be useful in evaluating questionable cystic renal lesions if CT imaging is inconclusive [1,2,7]. PRCC is characterised by its cystic appearance with thickened, irregular walls, "impure" fluid content and moderate acoustic enhancement .
The peculiarity of this case consists in the fact that the solid component of the cyst (the tumor itself) was less echogenic than the fluid surrounding it. This was due to recent intracystic hemorrhage.
On contrast-enhanced CT, PRCC appears generally hypovascular and enhances only 10-30 HU after intravenous administration of contrast material. Similarly, changes in signal intensity on MR images can be subtle (as low as 15% increase in signal intensity after contrast enhancement), reflecting the hypovascular nature of these tumors [1,2,7].
Herts et al suggested that a tumor characterized by a post contrast parenchyma-tumor density ratio over 25%, is unlikely to be a PRCC, and that a tumor with a low normal parenchyma-tumor or tumor-aorta ratio usually suggest a PRCC .Surgical resection remains the only known effective treatment for localized PRCC, and it also is used for palliation in metastatic disease .