Bilateral synchronous clear cell renal cell carcinoma with different morphological types

Clinical History

Gradually increasing mass of the right lumbar fossa.

Imaging Findings

The patient presented with a gradually increasing mass lesion of the right lumbar fossa. Laboratory studies were normal except for an elevated sedimentation rate of 82mm/h. Urinalysis was normal. CT showed a heterogeneous isodense mass in the right kidney and a homogeneous hypodense mass lesion in the left kidney. The lesion in the right kidney showed intense contrast enhancement. The lesion in the left showed septal and wall enhancement (Fig. 1). The lesion in the right kidney showed heterogeneous signals within the mass on both T1- and T2-weighted images (Figs 2a,c). The lesion showed prominent contrast enhancement (Fig. 2d). The lesion in the left kidney showed decreased signal intensity compared with the renal parenchyma on T1-weighted MR images (Fig. 2b). The internal septations became most clear after contrast medium injection (Fig. 2e). Mural nodules enhanced moderately. The lesion showed increased signal intensity on T2-weighted images.

A CT-guided needle aspiration biopsy of the masses and biopsy material taken during surgery from the right kidney (Fig 3)revealed a RCC, clear cell subtype, in both kidneys: predominantly solid in right kidney, predominantly cystic in left kidney.

Discussion

The clear cell subtype is the most frequently seen histological variant in renal cell carcinoma (RCC), accounting for approximately 70% of cases. Bilateral lesions are seen in 0.5-3% of cases (1). Most RCC of the clear cell subtype show solid lesions with necrotic portions. Almost completely cystic lesions make up 10% of clear cell RCC and they are always solitary (1,2). Most lesions are solitary and randomly distributed in the renal cortex. Multicentricity in the same kidney occurs in approximately 4% of cases. Multicentricity and bilaterality are often associated with the Von Hippel-Lindau syndrome (1,2). In this syndrome lesions tend to be bilateral and multicentric, are often associated with cysts and angiomyolipomas (AML), and occur at an earlier age than in sporadic RCC.

Clear cell RCC can be morphologically subdivided into predominantly cystic (most characteristic) and cystic. Cystic clear cell RCC constitutes approximately 10% of clear cell RCC and they are almost always cystic. Cystic clear-cell RCCs are always solitary and predominately affect the right kidney (75%). There is a clear male predominance (2:1).

CT and MRI are the methods of choice for evaluation and staging of renal tumours. On unenhanced CT sections, almost all clear cell RCC lesions are of heterogeneous appearance (3). Seventy five percent of cases enhance significantly after intravenous injection of contrast material while 20% show mild or no contrast enhancement. Intratumoral necrosis is almost always present especially in larger lesions (4). Cystic clear cell RCC lesions are detected as hypodense on unenhanced CT images. When present, a thick wall of the lesion or mural nodule will enhance after IV contrast medium administration. The imaging features of clear cell RCC on MRI predominantly vary by the presence of necrosis. Necrosis is hypointense on T1-weighted images and hyperintense on T2-weighted images. The enhancement pattern is almost always the same as seen on CT.

Differential Diagnosis List

Final Diagnosis

Bilateral renal cell carcinoma with different morphologic subtypes

URL:	https://www.eurorad.org/case/1424
DOI:	10.1594/EURORAD/CASE.1424
ISSN:	1563-4086