Renal cell carcinoma with a pelvicalyceal system tumor thrombus: a case report


 Background Renal cell carcinoma (RCCs) is the most common malignancy of the kidney. When RCC progresses, it is known to form tumor thrombus in the renal vein and/or inferior vena cava. However, RCC does not normally form tumor thrombus in the pelvicalyceal system. Case presentation A 56-year-old man presented to our department for the treatment of a renal tumor with asymptomatic gross hematuria. In a dynamic CT study, contrast enhancement revealed a tumor suspected to be RCC, but atypical finding as a tumor thrombus that filled the pelvicalyceal system was also observed. Nephroureterectomy was performed, and the tumor was diagnosed histopathologically as clear cell RCC and papillary RCC. Conclusion We report a rare case of RCC directly invading the pelvicalyceal system as a thrombus mass, with no microscopic individual tumor implants in the pelvicalyceal system wall, invasion of the renal vein, or invasion of adjacent organs. To our knowledge, only six such cases have been reported in English literature, and as a result, very few theories explaining pelvicalyceal system invasion have been presented. This highlights the signiﬁcance of adding invasion of the pelvicalyceal system as part of the most recent, updated tumor metastases classiﬁcation.

Nephroureterectomy was performed, and the tumor was diagnosed histopathologically as clear cell RCC and papillary RCC.

Conclusion
We report a rare case of RCC directly invading the pelvicalyceal system as a thrombus mass, with no microscopic individual tumor implants in the pelvicalyceal system wall, invasion of the renal vein, or invasion of adjacent organs. To our knowledge, only six such cases have been reported in English literature, and as a result, very few theories explaining pelvicalyceal system invasion have been presented. This highlights the significance of adding invasion of the pelvicalyceal system as part of the most recent, updated tumor metastases classification.

Background
Renal cell carcinoma (RCC) and adenocarcinoma account for about 85% of all solid neoplasms of the kidney [1], Advances in imaging technology have dramatically increased the incidence of all stages of RCC [2]. Goetzl et al. [3] reported that 51%-56% of renal cortical tumors are diagnosed incidentally. In 1978, the TNM system, which was rst used for staging RCC, was adopted by the Union Internationale Contrele Cancer (UICC) [4]. Identi cation of the prognostic factors for RCC is critical for analyzing patient survival as well as for evaluating treatment options. Several studies have revealed that the TNM stage is the most important prognostic factor [5]. Several revisions of the TNM system have been made by UICC and the American Joint Committee on Cancer (AJCC). RCC with a pelvicalyceal system tumor thrombus is rare, although a vein tumor thrombus is not uncommon in RCC. So far, it has been described in six English-language literatures [6]. Urinary Collecting System Invasion (UCSI) of RCC including tumor thrombus in the renal pelvis and/or ureter has not been classi ed in the UICC TNM classi cation because of less frequency [7]. The role of pelvicalyceal system tumor thrombus in prognosis is still undetermined.
What's more, RCC with pelvicalyceal system tumor thrombus is often misdiagnosed as transitional cell carcinoma (TCC) preoperatively. However, a correct preoperative or intraoperative diagnosis is very important to decide surgical strategy. And, one of the most important challenges in the treatment of nonmetastatic RCC patients is the detection of patients at risk for disease recurrence in order to tailor followup protocols and to assign these patients to potential adjuvant treatment protocols.
A thorough review of the medical literature reveals almost no data for the Chinese population. Consequently, We present a rare case of RCC, and we hope that it should be help to understand whether the presence of the pelvicalyceal system tumor thrombus plays a role in predicting patient survival.  (Fig. 1D). In addition, No obvious distant metastasis was observed on chest CT or bone scanning. Cystoscopy revealed no obvious tumorous lesion. The tumor was diagnosed as left RCC (cT3aN0M0), and transabdominal laparoscopic radical left nephroureterectomy and hilar lymph node dissection were performed. Also total ureterectomy was additionally performed, although intraoperative histopathological examination could rule out urothelial carcinoma. Histopathological examination: The macroscopic ndings of the excised tumor were a yellow color, and hemorrhage and necrosis were observed in its interior. There was cord-shaped tumor thrombus extending into pelvicalyceal system ( Fig. 2). Histologically, clear cell RCC with severe necrosis, invasion and proliferation were observed ( Fig. 3A, 3B), and papillary RCC (Fig. 3C, 3D). And no RCC was observed in lymph node. Immunostaining was positive for CD10 EMA and vimetin (Fig. 4A, 4B, 4C), negative for P504S (Fig. 4D). According to these ndings, the tumor was diagnosed as clear cell RCC and papillary RCC (pT3apN0). No malignancy was observed in the surrounding renal pelvic or ureteral mucosa.

Discussion And Conclusion
This case report presented a patient with thrombus-like tumor of renal cell carcinoma like transitional cell carcinoma of kidney. This presents di culty in differentiating between RCC and renal pelvis transitional cell carcinoma. To the best of our knowledge, our case is the rst reported pelvicalyceal system tumor thrombus in RCC in China.
Involvement of the urinary collecting system by renal cell carcinoma is rare in the absence of other poor prognostic features associated with the primary tumor. Clear cell carcinoma most commonly invades, while invasion by papillary tumors is rare. Due to the rarity of cases involving thrombus-like tumor into pelvicalyceal system, current staging system does not mentioned the importance of collecting system involvement in the TNM classi cation [8]. This case has unique pathology of mixed RCC between clear cell and papillary RCC, which extends into the collecting system without invading adjacent organs or extending outwards from the pelvicalyceal system wall.
On abdominal CT, the mass seems only lled renal pelvis, however it was found on macroscopic examination that the pelvicalyceal system were also lled by tumor thrombus, this phenomenon was very unique because the tumor thrombus lled the pelvicalyceal lumen instead of invading it.
In 2007, Gulati et al. reported the only other case of RCC that directly invaded from the renal pelvis into the ureter and formed a tumor thrombus [6]. A tumor thrombus is thought to advance into the vein due to pressure in the vein and the renal pelvis. Gulati et al. reported that venous pressure was increased due to the renal vein tumor thrombus and lymph node compression [6]. In the patient in this present report, there was neither microscopic venous invasion nor tumor thrombus in the renal vein, and no massive lymph node metastasis that was large enough to increase the venous pressure. Therefore, the tumor thrombus was thought to have spontaneously spread directly into the pelvicalyceal system.
Uzzo et al reported that no case of local involvement of the ureter by tumor was identi ed in 61 cases with UCSI [9]. It is controversial that whether UCSI should be added into TNM classi cation [10,11], however most reported UCSI of RCC to be a signi cant predictor of prognosis [9][10][11][12]. Thus, the case in the present report is very rare and must be followed up carefully.
In such cases, it is very important to make a correct preoperative diagnosis of the tumor type because the operative methods of TCC and RCC are different. Nephroureterectomy is suggested for treatment of TCC while nephrectomy for RCC [13]. Based on preoperative examinations including imaging procedures, we had di culty to differentiate it from renal pelvis transitional cell carcinoma. Thus, this case required careful consideration regarding surgery. Finally nephroureterectomy was performed, including resection of the ureter.
Antiangiogenic targeted therapy agents, usually consisting of multi-kinase inhibitors, have been used successfully to treat renal cell carcinomas [14]. Although the present results didn't very clearly show that collecting-system invasion are poor prognostic factor, we think that this patient should have access to targeted tyrosine kinase (TKI) or mammalian target of rapamycine (mTOR) inhibitor treatment after operation. RCC with pelvicalyceal system tumor thrombus is rare. A correct preoperative or intraoperative diagnosis is very important to decide surgical strategy. Intraoperative frozen section is recommended. Laparoscopic radical nephroureterectomy is a safe and feasible operative method in treatment of RCC with a pelvicalyceal system tumor thrombus. All of the patients were treated with targeted tyrosine kinase (TKI) or mammalian target of rapamycine (mTOR) inhibitor. It should be studied that a revised stage including patients with collecting-system invasion with tumor thrombus might improve its prognostic validity.

Availability of data and materials
All necessary information about this case report was presented in the manuscript. Raw data regarding our patients are not publicly available due to the respect and protection of our patients' privacy but are available from the corresponding authors upon reasonable request.

Competing interests
The authors declare that they have no competing interests.

Consent for publication
Written informed consent was obtained from the patients for the publication of this case report and any accompanying images.

Ethics approval and consent to participate
This report was approved by the Ethical Committee of Strategic Support Force Characteristic Medical Center, and written informed consent was obtained from the patients.