Collecting duct carcinoma (CDC) is a rare subtype of renal epithelial neoplasm, accounting for <2% of all the renal cell carcinoma (RCC) cases (1). This aggressive malignancy is considered to be derived from the collecting duct of the kidney and has a poor prognosis in the majority of patients (2–5) with a median survival time of only 22 months following nephrectomy (6). Despite the histological and immunohistochemical features of this disease, distinguishing CDC from pelvic urothelial carcinoma and high-grade papillary RCC is difficult, mainly due to the varying features of CDC (7). The tumor is usually identified in or proximal to the renal pelvis and appears gray or white without extensive necrosis or hemorrhage (8). Various treatments have been reported in the literature, including immunotherapy, radiation therapy, chemotherapy (5,9) and radical excision (3). In order to improve the understanding on the biological behavior of CDC, the present study reported the case of a 62-year-old female patient with typical pathological features of CDC. In addition, the clinical, pathological and immunohistochemical aspects of the disease were reviewed. Written informed consent was obtained from the patient.

In August 2013, a 62-year-old female was admitted to the First Hospital of Jilin University (Changchun, China) for evaluation of right-flank pain that had persisted for one month. The patient did not experience gross hematuria or dysuria. A physical examination was unremarkable, with the exception of mild percussion pain in the right kidney area. Blood examinations revealed an elevated erythrocyte sedimentation rate [41 ml/h; normal range, 4–30 ml/h (10)]. An abdominal ultrasonography scan demonstrated a solid, hypoechoic and relatively well-demarcated tumor, approximately 6.9×5.6 cm in size, occupying the right kidney. Contrast-enhanced computed tomography examination of the abdomen and pelvis revealed multiple hypoattenuating quasicircular lesions, 0.5–4.3 cm in size, in the upper pole of the right kidney. The mass presented minimal contrast enhancement following administration of Omnipaque contrast agent [100 ml; GE Healthcare (Shanghai) Co., Ltd., Shanghai, China] (Fig. 1). No evidence of renal vein invasion, lymph node or distant metastasis was observed.

Based on the clinical and imaging findings, a laparoscopic radical resection of the right kidney was performed in order to excise the tumor. Macroscopic examination of the resected tissue revealed a 4×4×3.5 cm tan-yellow, well-circumscribed, soft tumor, which was occupying almost the entire upper pole of the kidney. The tumor had invaded the renal pelvis and renal sinus fat, while a large area of necrosis and a satellite lesion were observed in the mass. In addition, a microscopic examination was performed and the characteristic features observed included a tubulopapillary growth pattern, significant pleomorphism of the neoplastic cells and local sarcomatoid changes (Fig. 2A). Thus, the tumor was classified as nuclear grade III using the Fuhrman grading system (11). Immunohistochemical analysis revealed that the tumor cells were strongly positive for epithelial membrane antigen (EMA; Fig. 2B) and cytokeratin (CK)7 (Fig. 2D). The tumor cells also reacted focally with vimentin (Fig. 2C); however, they were negative for CK20, CD10, uroplakin III and p63. Based on the histopathological and immunohistochemical findings, a diagnosis of CDC was established. The patient was discharged eight days after surgery and no further treatments were administered. A CT scan performed 10 months after surgery revealed no recurrence or metastasis.

CDC is a rare pathologic type of RCC, with a tendency towards early dissemination and high mortality rates (12,13). Although CDC is a rare tumor, its clinical presentation is nonspecific and may include symptoms of gross hematuria, backaches, weight loss and a local mass. In addition, the incidence of this tumor is higher in male adults aged between 41 and 71 years, with a 2:1 male to female ratio (14). At the time of diagnosis, the tumor is typically large, having a medullary origin and presenting with an infiltrative lesion. The majority of CDC tumors have been found to demonstrate focal cortical extension, while perirenal invasion was also common in large tumors (15). Since these tumors do not exhibit specific imaging features, a microscopic examination and immunohistochemical staining are required for the diagnosis of CDC (1). Microscopically, the common features include a tubulopapillary architecture, atypical hyperplastic changes, clear cytoplasm, evident stromal reaction with fiber hyperplasia and detached single cells with a hobnail surface (16). In the present case, the results of the microscopic examination revealed certain characteristic features of CDC, including a tubulopapillary growth pattern, significant pleomorphism of the neoplastic cells and local sarcomatoid changes. Positive immunohistochemical staining for CK19, CK7, 34βE12 and vimentin has been previously reported to support the diagnosis of CDC (17). In addition, a previous study demonstrated that the CDC cells also express EMA, peanut lectin agglutinin and Ulex europaeus agglutinin 1 (18). In the present study, immunohistochemical analysis demonstrated that the tumor cells were strongly positive for EMA and CK7, while they reacted focally with vimentin. Therefore, the patient was diagnosed with CDC.

Regarding the treatment modality, surgery is performed in the majority of patients as a primary treatment (13,19). In addition, a previous study demonstrated that combined chemotherapy with gemcitabine or carboplatin may be a promising treatment strategy for CDC patients, particularly those with advanced stage disease (20). However, radical nephrectomy or chemotherapy have not been found to effectively control the progressive form of this disease, due to the high rates of local recurrence and distant metastases (21). A previous study revealed that less than one third of patients survived for >2 years (15). In the present study, laparoscopic radical resection of the kidney was performed without chemotherapy or immunotherapy. No recurrence or metastasis was observed 10 months after surgery; however, further follow-up is required.

In conclusion, CDC is a rare, aggressive renal tumor that is frequently associated with nodal and visceral metastases at presentation. Since patients with CDC often present a poor prognosis, the early detection and diagnosis of this disease are vital. Histochemical and immunohistochemical analyses may provide adequate and reliable data in order to distinguish this tumor from other subtypes of RCC, resulting in the establishment of disease-specific treatment strategies.