Collecting duct carcinoma of the kidney: Imaging observations of a rare tumor

Abstract

Collecting duct carcinoma (CDC) is a rare type of renal neoplasm. Early diagnosis is possibly the only factor leading to a prolonged survival for patients with CDC. The purpose of the present study was to characterize the imaging features of CDC and improve its diagnosis. Radiological data of six patients were retrospectively reviewed by three experienced radiologists, including six cases examined with non-contrast computed tomography (CT) scans, five with contrast-enhanced CT scans, one with magnetic resonance urography, one with renal dynamic imaging and two with conventional whole-body ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT scans. All patients were pathologically confirmed with CDC. In total, seven tumors were detected in the six cases, with a mean size of 5.3 cm. Of the tumors, two were solid and the rest were complex solid and cystic. In addition, six tumors were located in medullary areas and only one tumor was found in the cortical location. Cystic components were observed in five tumors. Weak enhancements were observed in all six tumors examined with contrast-enhanced CT, and heterogeneous enhancements were also observed in the majority of these tumors with the exception of one tumor. Infiltrative growth and expansible growth were found in five and two tumors, respectively. Metastatic lesions were detected in all six patients. On MR urography, the involved kidney exhibited similar imaging observations to the CT scan. Renal dynamic imaging revealed a decreased renal function in the involved kidney and an increased renal function in the contralateral kidney. On PET/CT imaging, a marked uptake of ¹⁸F-FDG was found in primary and metastatic lesions. The results of the present study indicated that medullary location, weak and heterogeneous enhancement, infiltrative growth, damage of renal function in the involved kidney and a marked uptake of ¹⁸F-FDG are imaging observations commonly identified in patients with CDC. When a renal tumor exhibits these imaging features, CDC may be suggested as a valuable differential diagnosis.

Keywords: collecting duct carcinoma; computed tomography; kidney; positron emission tomography.

Figure 1

Imaging observations of patient 2. (A and B) Two tumors were identified in the left kidney. (C) Multiple lymph nodes were found in the renal hilum area, but no evidence of lymph nodes metastases was detected by pathological examination.

Figure 2

Imaging observations of patient 4. Coronal (A) contrast-enhanced computed tomography and (B) T2-weighted images showed the distention of the renal pelvis and ureter, as well as multiple nodular thickening of the wall of the ureter. (C) Fused image of the clearance phase of renal dynamic imaging failed to show the left kidney, which denoted that the renal function of the left kidney had been lost.

Figure 3

Imaging observations of patient 6. (A) Maximum intensity projection and (B and C) positron emmission tomography/computed tomography images showed a renal mass in the right kidney and multiple pleural metastases in the left thoracic cavity. A marked uptake of ¹⁸F-FDG was observed in each lesion.