CASE 9503 Published on 26.08.2011

Collecting duct carcinoma of the kidney: atypical imaging findings

Section

Uroradiology & genital male imaging

Case Type

Clinical Cases

Authors

Athina C. Tsili1, Maria I. Argyropoulou1, Persefoni N. Margariti1, Dimitrios Giannakis2, Sotirios Koukos2, Anna Gousia3, Nikolaos Sofikitis2, Konstantinos Tsampoulas1

1)Department of Clinical Radiology
2)Department of Urology
3)Department of Pathology
University Hospital of Ioannina, Greece

Pl. Patgis 2 45332 Ioannina, Greece;
Email:a_tsili@yahoo.gr
Patient

71 years, female

Categories
Area of Interest Kidney ; Imaging Technique Ultrasound, CT, MR
Clinical History
We report a case of a 71-year-old woman referred for CT and MRI of the abdomen in the setting of a non-cystic renal mass discovered incidentally during sonography. Routine laboratory analysis was unremarkable.
Imaging Findings
Sonography revealed the presence of a heterogenous mass arising from the upper pole of the left kidney (Figure 1). CT showed an expansile, sharply demarcated left renal mass (Figure 2) mainly hypodense on plain images with slightly hyperdense parts (Figure 2a), not enhancing after contrast material administration (Figure 2d). A thick hyperdense rim surrounded the mass(Figure 2a, c). Retroperitoneal lymphadenopathy was found to coexist (Figure 2b, f), suggesting the diagnosis of malignancy.
MR confirmed the presence of a renal mass(Figure 3). The tumor was mainly hyperintense on both T1-and T2-weighted images, suggestive for hemorrhagic content, surrounded by a hypointense halo, which corresponded to a fibrous pseudocapsule confirmed on histopathology.
Left radical nephrectomy showed a high-grade collecting duct carcinoma, with invasion of the perinephric fat (Figure 4, stage pT3a). The patient underwent systemic chemotherapy, and on follow-up CT, one year after surgery, showed remission of retroperitoneal lymph nodes (Figure 5).
Discussion
Background
According to 2004 WHO classification renal cell carcinoma (RCC) includes five main histologic subtypes, including conventional (clear cell), papillary, chromophobe, collecting duct and unclassified RCC [1]. Renal cystic lesions on the other hand are categorized according to Bosniak classification into four types: category I, including simple benign fluid-containing cysts, category II, including minimally complicated benign cysts, category III, that is indeterminate cystic lesions, not adequately characterized based on imaging features, and category IV, including highly suspicious for malignancy cystic masses [2,3].
Collecting duct carcinoma of the kidney is a rare histologic subtype of RCC, accounting for less than 1% of renal malignancies [1,4,5]. This aggressive malignancy originates from the distal collecting ducts of Bellini [1, 4-12]. The neoplasm may be diagnosed at advanced stage, as in this case. The prognosis is poor, with less than 30% of patients surviving more than two years.
Imaging perspective
Imaging features of collecting duct carcinoma of the kidney are variable and preoperative characterization is usually difficult. On sonography, collecting duct carcinoma may appear as hyperechoic, isoechoic or hypoechoic compared to the surrounding normal renal parenchyma [1]. CT imaging findings include medullary location, involvement of the renal sinus, preservation of the renal contour, and minimal contrast enhancement [6-9]. The preservation of the normal renal contour and the involvement of the renal sinus are associated with the origin and growth pattern of the collecting duct carcinoma. Although not specific, these CT features may suggest the preoperative diagnosis. MR imaging findings include variable signal intensity on T1-weighted images, and lesion hypointensity on T2-weighted images.
This case is an atypical example of collecting duct carcinoma, detected as an expansile, mainly exophytic renal tumor, with minor involvement of the renal sinus. Lack of contrast enhancement may be related to the presence of hemorrhagic content and minimal tumor vascularity, although this finding has been reported also with papillary RCC.
The presence of a pseudocapsule surrounding renal cell carcinoma (RCC) is a pathologic feature seen frequently in early stages of disease, usually in small tumor size and low histologic grade [13-15]. However, renal pseudocapsule may be seen in large, aggressive tumors, as it was in this patient. MRI has been reported as a reliable imaging modality for the detection of renal pseudocapsule, seen as hypointense halo surrounding the tumor o T2-weighted images[13-15]. Herein, renal pseudocapsule was also visible by both unenhanced and contrast-enhanced CT images, as a thick hyperdense rim.
Differential Diagnosis List
Collecting duct carcinoma of the kidney
Transitional cell carcinoma of the pelvicaliceal system
Renal medullary carcinoma
Renal lymphoma
Renal metastases
Renal cell carcinoma arising from a column of Bertin
Mesoblastic nephroma
Bacterial pyelonephritis
Final Diagnosis
Collecting duct carcinoma of the kidney
Case information
URL: https://www.eurorad.org/case/9503
DOI: 10.1594/EURORAD/CASE.9503
ISSN: 1563-4086

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