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Korean J Urol Oncol > Volume 15(3); 2017 > Article
Jung, Oh, and Shin: Collecting Duct Carcinoma (Bellini Duct Carcinoma) Presented as a Renal Cyst


Renal cysts are frequently seen in the general population. Most small simple renal cysts are managed by conservative treatment. A renal cell carcinoma (RCC) presenting as a renal cyst is extremely uncommon, and collecting duct carcinoma is a rare type of RCC. This report describes a collecting duct carcinoma initially presnted as a renal cyst. The patient was a 52-year-old man who had been diagnosed with a renal cyst in the left lower pole 8 years earlier but was not regularly follow-up. He presented with left flank pain and gross hematuria. Computed tomography revealed a heterogeneous enhanced mass in the left lower pole and multiple para-aortic lymph nodes. He underwent radical nephrectomy and lymph nodes dissection which confirmed collecting duct carcinoma with sarcomatoid differentiation.

A renal cell carcinoma (RCC) presenting as a renal cyst is extremely rare. Most simple renal cysts are treated conservatively. However, symptoms may occur, requiring renal cyst aspiration and/or sclerotherapy or laparoscopic marsupialization.
Collecting duct carcinoma (Bellini duct carcinoma) is a rare form of RCC. Collecting duct carcinomas metastasize to regional lymph nodes in approximately 80% of patients. The prognosis of patients with collecting duct carcinoma is poor.
This study describes a patient who had been diagnosed with a renal cyst 8 years earlier, that confirmed collecting duct carcinoma with regional lymph nodes metastases.


A 52-year old man was referred to a urology outpatient clinic for left flank pain and gross hematuria. The patient had been treated with coiling for a cerebral aneurysm, and had visited the Emergency Department for left flank pain 8 years ago. At that time, a computed tomography (CT) scan showed a 4.0-cm-sized renal cyst located in the lower pole of the left kidney (Fig. 1). There was no family history of renal cysts, renal cystic disease or renal malignancy. He was treated conservatively, but did not present further follow-up. After 8 years, he presented with flank pain and gross hematuria. Urine analysis showed 5–9 white blood cells per high-power field (HPF) and over one-half red blood cell per HPF. Cystoscopy showed a bloody efflux through the left ureteral orifice. CT scan showed a 4.7-cm-sized heterogeneously enhanced lesion in the lower pole of the left kidney (Fig. 2) and multiple enlarged para-aortic lymph nodes (Fig. 3). He underwent radical nephrectomy with lymph node dissection. The resected left kidney was enlarged and measured 13.5 cm×7.5 cm×4.5 cm. The cut surface of the kidney showed the presence of a yellowish white tumor in the lower pole, predominantly in the renal medulla, and measuring 5.1 cm×3.7 cm. The tumor showed infiltrating margins and focal extension to the perinephric fat with focal hemorrhage and necrosis (Fig. 4). Sections of the tumor revealed a biphasic growth pattern, consisting of carcinomatous and sarcomatous components. The carcinomatous areas were composed of tubules and angulated glands in desmoplastic stroma with marked inflammatory cell infiltration (Fig. 5A). The carcinomatous cells presented a hobnail pattern and displayed Fuhrman nuclear grade 4 (Fig. 5B). The sarcomatous component was focal (10% of the entire tumor), consisting of spindle and plump or epithelioid cells with high mitotic activity (Fig. 5C). The stroma was desmoplastic, containing abundant lymphocytic infiltrates. The central necrotic area showed hemor-rhagic necrosis, but an epithelial lined cyst was not present. The tumor extended to the renal parenchyma with multiple satellite tumor nodules and multiple lymphovascular tumor emboli. The adjacent urothelial lining of the renal pelvis and ureter showed mild hyperplasia without atypia, and there was no evidence of urothelial carcinoma. Immunohistochemical analyses were performed using formal-in-fixed, paraffin-embedded sections. Cells of carcinomatous areas were positive for cytokeratin 7 (Fig. 6A), cytokeratin 19, vimentin (Fig. 6B), and PAX 8 (Fig. 6C). Sarcomatous cells were positive for cytokeratin and vimentin. The tumor was negative for immunostaining with c-Kit (CD117), CD10, and p63 (Fig. 6D). Six excised hilar lymph nodes and 2 excised para-aortic lymph nodes showed multiple metastatic deposits. The tumor was staged as pT3 N1 M0.
Fig. 1.
Computed tomography showing a renal cyst sized 4 cm×4 cm in the left kidney.
Fig. 2.
Computed tomography showing a heterogeneous enhanced mass sized 4.7 cm×4 cm in the left kidney.
Fig. 3.
Computed tomography showing a renal cyst (A), a kidney mass with enlarged para-aortic lymph node (B). C: renal cyst, M: mass. Arrow indicates para-aortic lymph node.
Fig. 4.
Nephrectomy specimen shows a whitish yellow ill-defined mass (star) located in the medulla of the lower pole with perirenal fat infiltration (black arrows). Hemorrhage and necrotic area (white arrow) is located in center of tumor.
Fig. 5.
The carcinomatous areas were composed of tubules and angulated glands in desmoplastic stroma (A; H&E, ×100) with a hobnail pattern and displayed high nuclear grade (B; H&E, ×200). The sarcomatous component shows spindle and plump or epithelioid cells with high mitotic activity (C; H&E, ×200).
Fig. 6.
Immunohistochemical stains of the tumor. Positive staining for cytokeratin 7 (A, ×200), vimentin (B, ×200), and PAX 8 (C, ×200). Negative staining for p63 (D, ×200) in carcinomatous areas.


The increased use of radiologic imaging as an investigative tool has led to frequent incidental discovery of renal cysts in the general population. Renal cysts have been caterorized as into Bosniak Classifications I, II, IIF, III, and IV.1
Only a few cases of RCCs appearing as simple renal cyst have been reported to date in the English literature with all of these tumors being clear cell carcinomas (Table 1).25 All of these patients were middle aged and Asian descent.
Table 1.
Renal cell carcinoma presenting simple renal cyst: a review of the literature
Study Race Age (yr) Sex Size (cm) Duration Management for renal cyst RCC type Metastasis
Takao et al.2 Japanese 54 Male 4 - Cyst aspiration Clear cell  
Sakai et al.3 Japanese 43 Male 6 6 yr Regular sonographic follow-up Clear cell  
Lin et al.4 Chinese 48 Male 11.5×9×16 - Cyst aspiration Clear cell  
Yu el al.5 Chinese 39 Female 7×6 - Laparoscopic marsupialization Clear cell  
Present case Korean 52 Male 5.1 8 yr Observation Collecting duct Regional lymph node

RCC: renal cell carcinoma.

The patient was diagnosed with a renal cyst at initial CT. In real clinical settings, sometimes clinicians may miss a minute solid portion in the renal cyst on initial CT scan because of the CT setting (kVs, mAs parameter, or slicing thickness, etc.). Ultrasonography may help evaluation for these renal cysts. However, this patient was not evaluated by ultrasonography because this was his first visit to the Emergency Department. Recent investigations shows that contrast-enhanced ultrasonography may assist in the evaluation of kidney masses.6 So serial follow-up is required to detect changes in renal cysts. For example, periodic follow-up found that a renal cyst had changed to a septated renal cyst and finally to a cystic RCC.3 However our patient was not regularly followed-up after diagnosis.
Collecting duct carcinoma is a rare presentation of RCC, constituting <1% of RCCs.7 Radical nephrectomy is a treatment of choice. About 80% of patients have regional lymph node metastases at diagnosis. Our patient showed metastasis to para-aortic lymph nodes. Radiotherapy, chemotherapy and immunotherapy have limited efficacy and the efficacy of targeted therapy is unclear. As the tumor cells spread in the cortical collecting tubule, the lesion develops characteristics similar to those of upper tract urothelial carcinoma.8 Collecting duct carcinoma must also be differentiated from urothelial carcinoma. Immunohistochemistry showed that PAX8 positivity and the absence of p63 had a 100% specificity and positive predictive value of 100% in diagnosis of collecting duct carcinoma.9 The prognosis of patients with these tumors is poor, especially as these tumors include sarcomatoid components.10
To our knowledge, this is the first report of a collecting duct carcinoma with sarcomatoid differentiation presenting as a renal cyst.
Because even radiologically simple renal cysts have a potential for malignancy, patients should be followed-up at regular intervals. Renal cysts showing even minimal changes on image modalities, should be further evaluated and treated.

Conflict of Interest

The authors claim no conflicts of interest.


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