DOI: 10.1148/rg.261055060
RadioGraphics 2006;26:233-244
© RSNA, 2006
Renal Cell Carcinoma: Unusual Imaging Manifestations1
Adilson Prando, MD,
Decio Prando, MD and
Patricia Prando, MD
1 From the Department of Radiology, Hospital Vera Cruz, Av Andrade Neves 402, Campinas, SP, 13013–161, Brazil (A.P., P.P.), and Unidade Radiológica Paulista, São Paulo, SP, Brazil (D.P.). Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received March 23, 2005; revision requested May 2 and received May 19; accepted June 8. All authors have no financial relationships to disclose.
Address correspondence to A.P. (e-mail: aprando{at}mpc.com.br).
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Abstract
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Unusual radiologic manifestations of a renal cell carcinoma (RCC) can present a diagnostic challenge. These manifestations include bilateral synchronous multifocal tumors, a small RCC with synchronous adrenal metastasis, and RCC associated with bulky abdominal lymphoma. Less common manifestations include multiseptated cystic carcinoma simulating a moderately complex renal cyst at ultrasonography (US), paraaortic metastatic adenopathy as the only sign of an undetectable primary renal neoplasm, RCC causing a large arteriovenous fistula, RCC simulating angiomyolipoma, and a nonfunctioning kidney due to transparenchymal renal propagation of cancer associated with a tumor thrombus occluding the renal vein. Radiologists should be aware of the possibility of tumor multifocality or of adrenal metastases from a high-grade small renal tumor, as well as of the association of RCC with lymphoma. They should also be aware of the importance of following up a multiseptated cystic mass found at US or a Bosniak category IIF renal cyst, since these lesions can serve as early indicators of cystic carcinoma. Because the clinical implications of and therapeutic strategies for RCC vary depending on imaging characterization of the nature and extent of the disease, familiarity with its more unusual radiologic manifestations facilitates accurate diagnosis and management.
© RSNA, 2006
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- Identify some uncommon radiologic appearances of renal cell carcinoma and discuss their clinical significance.
- Describe the role of the radiologist in characterizing these unusual manifestations of renal cell carcinoma.
- Discuss the correlation between the clinical, radiologic, and pathologic features of these manifestations.
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Introduction
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Renal cell carcinoma (RCC) is the most common cancer of the kidney and accounts for about 2% of adult malignancies (1). At times, this neoplasm is characterized by varied and obscure clinical and radiologic features, which include unusual meta-static sites and paraneoplastic, paraendocrine, serologic, and vascular syndromes (1,2). When the imaging findings are atypical, the preoperative diagnosis of RCC can be extremely difficult. It is important for radiologists to be familiar with these unusual manifestations of RCC.
We retrospectively reviewed the medical records and imaging studies of 27 of 469 patients with histologically proved RCC who were evaluated at our institutions over the past 12 years. In this article, we discuss and illustrate some uncommon radiologic manifestations of RCC and their correlation with clinical and pathologic findings. These manifestations include bilateral synchronous multifocal RCCs, synchronous adrenal metastasis from RCC, RCC associated with bulky abdominal lymphoma, multiseptated cystic carcinoma simulating a moderately complex renal cyst at ultrasonography (US), paraaortic metastatic adenopathy as the only sign of an undetectable primary renal neoplasm, RCC causing a large arteriovenous fistula, spontaneous perirenal hematoma seen prior to the radiologic depiction of RCC, RCC simulating an exophytic angiomyolipoma, and a nonfunctioning kidney caused by transparenchymal renal propagation of RCC and renal vein thrombosis.
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Bilateral Synchronous Multifocal RCCs
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Bilateral synchronous RCCs are a challenging surgical problem and occur in approximately 4% of all patients with RCC (3). Bilateral RCCs of the same subtype can exist in a hereditary form (von Hippel–Lindau disease, hereditary papillary RCC) or a sporadic form (3). Hereditary forms of bilateral RCCs are more common than sporadic forms and generally occur at an earlier age. Published reports suggest that less than 2% of patients with sporadic RCC have bilateral neoplasms (4). Sporadic bilateral synchronous RCCs can be of either the clear cell or papillary subtype (5).
Tumor multifocality is defined as the presence of more than one ipsilateral or contralateral RCC of the same histologic subtype (6). The prevalence of multifocality is greater in patients with bilateral synchronous RCCs than in those with unilateral RCC and was observed in six of 11 patients in our series who presented with bilateral synchronous renal tumors. To detect multifocal RCCs at histopathologic examination, the kidney should be serially and systematically cut (3- or 5-mm sections) to probe for intraparenchymal lesions (7). Multifocal renal lesions have an average size of 8.7 x 9.0 x 9.5 mm (range, 3–23 mm); occasionally, however, they can be quite large. Tumor multifocality is demonstrated at preoperative imaging in only one-third of patients (7,8). In RCC, multifocality cannot be predicted reliably, although bilaterality and the papillary subtype seem to be associated with a higher prevalence of multifocality. This histologic subtype of RCC frequently appears at computed tomography (CT) as a hypovascular mass (Fig 1). There is still controversy regarding the relationship between tumor grade and stage and the prevalence of multifocality (7,8).
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Figure 1a. Sporadic bilateral synchronous multifocal RCC in a 62-year-old man with weight loss and hematuria. (a, b) Axial contrast material–enhanced CT scans through the abdomen show large, well-defined renal masses (M) with low attenuation and poor enhancement. Several hypo-attenuating solid nodules (eight on the right, 10 on the left) of varying size (arrows) were seen in the kidneys. (c) Intraoperative photograph of the left kidney illustrates numerous superficial tumors. Conservative resection of 11 tumors was subsequently performed. (d) Photograph of the gross specimen shows four of these tumors in the upper pole of the right kidney. Note the small amount of normal renal parenchyma (arrows) between the tumors.
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Figure 1b. Sporadic bilateral synchronous multifocal RCC in a 62-year-old man with weight loss and hematuria. (a, b) Axial contrast material–enhanced CT scans through the abdomen show large, well-defined renal masses (M) with low attenuation and poor enhancement. Several hypo-attenuating solid nodules (eight on the right, 10 on the left) of varying size (arrows) were seen in the kidneys. (c) Intraoperative photograph of the left kidney illustrates numerous superficial tumors. Conservative resection of 11 tumors was subsequently performed. (d) Photograph of the gross specimen shows four of these tumors in the upper pole of the right kidney. Note the small amount of normal renal parenchyma (arrows) between the tumors.
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Figure 1c. Sporadic bilateral synchronous multifocal RCC in a 62-year-old man with weight loss and hematuria. (a, b) Axial contrast material–enhanced CT scans through the abdomen show large, well-defined renal masses (M) with low attenuation and poor enhancement. Several hypo-attenuating solid nodules (eight on the right, 10 on the left) of varying size (arrows) were seen in the kidneys. (c) Intraoperative photograph of the left kidney illustrates numerous superficial tumors. Conservative resection of 11 tumors was subsequently performed. (d) Photograph of the gross specimen shows four of these tumors in the upper pole of the right kidney. Note the small amount of normal renal parenchyma (arrows) between the tumors.
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Figure 1d. Sporadic bilateral synchronous multifocal RCC in a 62-year-old man with weight loss and hematuria. (a, b) Axial contrast material–enhanced CT scans through the abdomen show large, well-defined renal masses (M) with low attenuation and poor enhancement. Several hypo-attenuating solid nodules (eight on the right, 10 on the left) of varying size (arrows) were seen in the kidneys. (c) Intraoperative photograph of the left kidney illustrates numerous superficial tumors. Conservative resection of 11 tumors was subsequently performed. (d) Photograph of the gross specimen shows four of these tumors in the upper pole of the right kidney. Note the small amount of normal renal parenchyma (arrows) between the tumors.
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Synchronous Adrenal Metastasis from RCC
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The risk of synchronous ipsilateral adrenal involvement from RCC ranges from 1% to 7% (9–13). Only multifocality, vascular invasion, and the presence of distant metastases are independent variables predictive of adrenal metastasis (13). Synchronous contralateral adrenal involvement is even more unusual. Adrenal metastases are very rare in stage T1 tumors (9,12). In our series, we found four patients with synchronous ipsilateral or contralateral solitary adrenal metastases from RCC. Two of these patients presented with ipsilateral adrenal involvement from a stage T2 tumor located at the upper pole of the left kidney. The other two patients presented with a highly unusual finding: an adrenal metastasis from a small RCC (<5 cm in diameter) located in the midportion of the kidney. This spread was considered to be hematogenous in nature (Figs 2, 3). CT is a very reliable tool for the preoperative evaluation of the adrenal gland in patients with RCC. The negative and positive predictive values of CT are 100% and 92.8%, respectively (14).
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Figure 2. Ipsilateral synchronous adrenal metastasis from an RCC in a 47-year-old man. Axial gadolinium-enhanced fat-saturated T1-weighted magnetic resonance (MR) image (repetition time msec/echo time msec = 1219/11) shows a large, heterogeneously enhancing solid mass (M) in the left adrenal gland. Note the small RCC (Fuhrman nuclear grade 4, pT1N0M1) (arrows) in the posterior aspect of the midportion of the left kidney.
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Figure 3a. Contralateral synchronous adrenal metastasis from an RCC in a 70-year-old woman with left flank pain. (a) Contrast-enhanced abdominal CT scan depicts a heterogeneous, well-defined, enhancing solid mass (M) in the left adrenal gland associated with a small, solid hypovascular RCC (Fuhrman nuclear grade 3, pT1N0M1) (arrows) in the medial aspect of the right kidney. (b) CT scan obtained inferior to a more clearly depicts the RCC (arrows).
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Figure 3b. Contralateral synchronous adrenal metastasis from an RCC in a 70-year-old woman with left flank pain. (a) Contrast-enhanced abdominal CT scan depicts a heterogeneous, well-defined, enhancing solid mass (M) in the left adrenal gland associated with a small, solid hypovascular RCC (Fuhrman nuclear grade 3, pT1N0M1) (arrows) in the medial aspect of the right kidney. (b) CT scan obtained inferior to a more clearly depicts the RCC (arrows).
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RCC Associated with Bulky Abdominal Lymphoma
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There was a higher than expected concurrence of RCC with non-Hodgkin lymphoma in our study (15,16). Imaging findings alone usually did not allow clear differentiation between these two entities. Despite the controversy regarding the pathophysiologic relationship between these entities, several case reports as well as a few retrospective studies have shown an increased coexistence. In our series, we observed three patients with RCCs confined to the kidney; these neoplasms were associated with bulky abdominal non-Hodgkin lymphoma. A common genetic mutation or an immunomodulatory role of the first malignancy predisposing to the second may explain this unusual association, but further investigation is warranted (15). Knowledge of this association is essential to avoid misdiagnosis as lymph node metastases from an RCC or as lymphomatous renal involvement (Fig 4).
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Figure 4a. RCC associated with bulky non-Hodgkin lymphoma in a 65-year-old man with right flank pain and hematuria. Axial contrast-enhanced CT scans through the abdomen reveal a heterogeneous, well-defined mass (M) with soft-tissue attenuation in the upper pole of the right kidney. The mass is associated with an unexpected focal hypoattenuating splenic lesion (L); bulky retroperitoneal adenopathy (N); and enlarged lymph nodes in the retrocrural region (* in b), adjacent to the right crus (* in a), and in the right cardiophrenic area (arrow in d). Percutaneous biopsy of the mass and of the retroperitoneal adenopathy revealed RCC and non-Hodgkin lymphoma, respectively.
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Figure 4b. RCC associated with bulky non-Hodgkin lymphoma in a 65-year-old man with right flank pain and hematuria. Axial contrast-enhanced CT scans through the abdomen reveal a heterogeneous, well-defined mass (M) with soft-tissue attenuation in the upper pole of the right kidney. The mass is associated with an unexpected focal hypoattenuating splenic lesion (L); bulky retroperitoneal adenopathy (N); and enlarged lymph nodes in the retrocrural region (* in b), adjacent to the right crus (* in a), and in the right cardiophrenic area (arrow in d). Percutaneous biopsy of the mass and of the retroperitoneal adenopathy revealed RCC and non-Hodgkin lymphoma, respectively.
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Figure 4c. RCC associated with bulky non-Hodgkin lymphoma in a 65-year-old man with right flank pain and hematuria. Axial contrast-enhanced CT scans through the abdomen reveal a heterogeneous, well-defined mass (M) with soft-tissue attenuation in the upper pole of the right kidney. The mass is associated with an unexpected focal hypoattenuating splenic lesion (L); bulky retroperitoneal adenopathy (N); and enlarged lymph nodes in the retrocrural region (* in b), adjacent to the right crus (* in a), and in the right cardiophrenic area (arrow in d). Percutaneous biopsy of the mass and of the retroperitoneal adenopathy revealed RCC and non-Hodgkin lymphoma, respectively.
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Figure 4d. RCC associated with bulky non-Hodgkin lymphoma in a 65-year-old man with right flank pain and hematuria. Axial contrast-enhanced CT scans through the abdomen reveal a heterogeneous, well-defined mass (M) with soft-tissue attenuation in the upper pole of the right kidney. The mass is associated with an unexpected focal hypoattenuating splenic lesion (L); bulky retroperitoneal adenopathy (N); and enlarged lymph nodes in the retrocrural region (* in b), adjacent to the right crus (* in a), and in the right cardiophrenic area (arrow in d). Percutaneous biopsy of the mass and of the retroperitoneal adenopathy revealed RCC and non-Hodgkin lymphoma, respectively.
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Multiseptated Cystic Carcinoma
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In the Bosniak classification system for renal cysts, complex cystic lesions manifesting with an increased number of septa or with minimal thickening of the septa or cyst wall are referred to as category IIF lesions (F stands for "follow-up"). These lesions must be followed up with imaging studies to show their stability over time and thereby prove their benignity. Follow-up CT will reveal that the great majority (95%) of these lesions are benign (17). Lesions containing thicker or irregular septa are considered category III lesions. At follow-up, multiloculated renal cysts with three or more septa (categories IIF and III) grow more rapidly than simple cysts (18). Rarely, cystic RCC may eventually manifest as a moderately complex renal cyst (multiseptated or cystic Bosniak category IIF lesion) at ultrasonography (US). In this situation, the lesion changes over time in size and morphologic features, developing thicker septa or enhancing mural nodules characteristic of a cystic (Bosniak category IV) or pre-dominantly solid RCC (19). For these reasons, follow-up of category IIF lesions is entirely appropriate (17). This change from a category IIF lesion to a category IV lesion was observed in two patients in our series. One patient refused further evaluation and returned for follow-up 4 years later complaining of hematuria. A complex renal cyst (Bosniak category IV) was demonstrated at CT, and surgery helped confirm the presence of a cystic RCC (Fig 5).
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Figure 5a. Multiseptated cystic carcinoma simulating a moderately complex renal cyst in a previously asymptomatic 57-year-old man. (a) US image of the right kidney shows a well-defined, complex cystic mass (arrows) containing four thick internal septa. The patient returned for evaluation 4 years later, presenting with flank pain and gross hematuria. (b) On a US image of the right kidney, the cystic mass (arrows) is seen to contain several solid nodular components. (c) Contrast-enhanced CT scan helps confirm the presence of a Bosniak category IV complex renal cyst (arrows). Note the presence of several enhancing soft-tissue components within the cyst. Over time, a multiseptated cystic RCC changes morphologically to a Bosniak category IV lesion due to the development of thicker septa and a nodular component. (d) Photograph of the gross specimen illustrates the appearance of a cystic RCC. (Case courtesy of Milton Nóbrega Filho, MD, Maximagem-Diagnóstico por Imagem, Recife, PE, Brazil.)
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Figure 5b. Multiseptated cystic carcinoma simulating a moderately complex renal cyst in a previously asymptomatic 57-year-old man. (a) US image of the right kidney shows a well-defined, complex cystic mass (arrows) containing four thick internal septa. The patient returned for evaluation 4 years later, presenting with flank pain and gross hematuria. (b) On a US image of the right kidney, the cystic mass (arrows) is seen to contain several solid nodular components. (c) Contrast-enhanced CT scan helps confirm the presence of a Bosniak category IV complex renal cyst (arrows). Note the presence of several enhancing soft-tissue components within the cyst. Over time, a multiseptated cystic RCC changes morphologically to a Bosniak category IV lesion due to the development of thicker septa and a nodular component. (d) Photograph of the gross specimen illustrates the appearance of a cystic RCC. (Case courtesy of Milton Nóbrega Filho, MD, Maximagem-Diagnóstico por Imagem, Recife, PE, Brazil.)
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Figure 5c. Multiseptated cystic carcinoma simulating a moderately complex renal cyst in a previously asymptomatic 57-year-old man. (a) US image of the right kidney shows a well-defined, complex cystic mass (arrows) containing four thick internal septa. The patient returned for evaluation 4 years later, presenting with flank pain and gross hematuria. (b) On a US image of the right kidney, the cystic mass (arrows) is seen to contain several solid nodular components. (c) Contrast-enhanced CT scan helps confirm the presence of a Bosniak category IV complex renal cyst (arrows). Note the presence of several enhancing soft-tissue components within the cyst. Over time, a multiseptated cystic RCC changes morphologically to a Bosniak category IV lesion due to the development of thicker septa and a nodular component. (d) Photograph of the gross specimen illustrates the appearance of a cystic RCC. (Case courtesy of Milton Nóbrega Filho, MD, Maximagem-Diagnóstico por Imagem, Recife, PE, Brazil.)
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Figure 5d. Multiseptated cystic carcinoma simulating a moderately complex renal cyst in a previously asymptomatic 57-year-old man. (a) US image of the right kidney shows a well-defined, complex cystic mass (arrows) containing four thick internal septa. The patient returned for evaluation 4 years later, presenting with flank pain and gross hematuria. (b) On a US image of the right kidney, the cystic mass (arrows) is seen to contain several solid nodular components. (c) Contrast-enhanced CT scan helps confirm the presence of a Bosniak category IV complex renal cyst (arrows). Note the presence of several enhancing soft-tissue components within the cyst. Over time, a multiseptated cystic RCC changes morphologically to a Bosniak category IV lesion due to the development of thicker septa and a nodular component. (d) Photograph of the gross specimen illustrates the appearance of a cystic RCC. (Case courtesy of Milton Nóbrega Filho, MD, Maximagem-Diagnóstico por Imagem, Recife, PE, Brazil.)
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Paraaortic Metastatic Adenopathy
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RCC has a tendency to metastasize early, sometimes before the primary tumor has become apparent (20,21). In the majority of patients in whom the initial complaint is related to distant metastases, radiologic evaluation may reveal a silent, concomitant renal malignancy. The initial lymphatic metastases from an RCC usually occur in the paraaortic and paracaval regional lymph nodes, both above and below the renal vessels (1). Two patients in our series presented with left-sided paraaortic lymph node metastases from RCC with no detectable primary neoplasm. The presence of nodal metastases without radiologic evidence of a renal tumor is very rare. Instead, nodal metastases are typically associated with an advanced-stage and -grade primary tumor, venous involvement, and distant metastases (22). In our two patients, the primary neoplasm was radiologically evident 6 and 36 months, respectively, after initial imaging work-up (Fig 6 ).
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Figure 6a. Paraaortic lymph node metastasis from an undetected RCC in a 55-year-old woman with left flank pain. (a) Contrast-enhanced helical CT scan shows an enlarged left paraaortic lymph node (arrow) and a normal left kidney. Surgery was performed to remove the enlarged lymph node and also demonstrated a normal left kidney. (b) Photomicrograph (original magnification, x40; hematoxylineosin stain) of the surgically removed left paraaortic lymph node shows renal carcinoma cells. (c) Contrast-enhanced turbo spin-echo T1-weighted MR image (536/11) obtained 6 months after initial imaging work-up shows a normal-appearing left kidney. (d) Contrast-enhanced helical CT scan obtained 3 years after initial imaging work-up shows a well-defined, enhancing mass (M) with soft-tissue attenuation occupying the medial aspect of the left kidney and causing mild hydronephrosis. (e) Contrast-enhanced helical CT scan obtained inferior to d 2 weeks later with the patient prone shows the soft-tissue mass (M). CT-guided percutaneous biopsy of the mass was performed. (f) Photomicrograph (original magnification, x40; hematoxylineosin stain) of tissue obtained at CT-guided percutaneous biopsy reveals clear cell renal carcinoma in a solid arrangement.
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Figure 6b. Paraaortic lymph node metastasis from an undetected RCC in a 55-year-old woman with left flank pain. (a) Contrast-enhanced helical CT scan shows an enlarged left paraaortic lymph node (arrow) and a normal left kidney. Surgery was performed to remove the enlarged lymph node and also demonstrated a normal left kidney. (b) Photomicrograph (original magnification, x40; hematoxylineosin stain) of the surgically removed left paraaortic lymph node shows renal carcinoma cells. (c) Contrast-enhanced turbo spin-echo T1-weighted MR image (536/11) obtained 6 months after initial imaging work-up shows a normal-appearing left kidney. (d) Contrast-enhanced helical CT scan obtained 3 years after initial imaging work-up shows a well-defined, enhancing mass (M) with soft-tissue attenuation occupying the medial aspect of the left kidney and causing mild hydronephrosis. (e) Contrast-enhanced helical CT scan obtained inferior to d 2 weeks later with the patient prone shows the soft-tissue mass (M). CT-guided percutaneous biopsy of the mass was performed. (f) Photomicrograph (original magnification, x40; hematoxylineosin stain) of tissue obtained at CT-guided percutaneous biopsy reveals clear cell renal carcinoma in a solid arrangement.
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Figure 6c. Paraaortic lymph node metastasis from an undetected RCC in a 55-year-old woman with left flank pain. (a) Contrast-enhanced helical CT scan shows an enlarged left paraaortic lymph node (arrow) and a normal left kidney. Surgery was performed to remove the enlarged lymph node and also demonstrated a normal left kidney. (b) Photomicrograph (original magnification, x40; hematoxylineosin stain) of the surgically removed left paraaortic lymph node shows renal carcinoma cells. (c) Contrast-enhanced turbo spin-echo T1-weighted MR image (536/11) obtained 6 months after initial imaging work-up shows a normal-appearing left kidney. (d) Contrast-enhanced helical CT scan obtained 3 years after initial imaging work-up shows a well-defined, enhancing mass (M) with soft-tissue attenuation occupying the medial aspect of the left kidney and causing mild hydronephrosis. (e) Contrast-enhanced helical CT scan obtained inferior to d 2 weeks later with the patient prone shows the soft-tissue mass (M). CT-guided percutaneous biopsy of the mass was performed. (f) Photomicrograph (original magnification, x40; hematoxylineosin stain) of tissue obtained at CT-guided percutaneous biopsy reveals clear cell renal carcinoma in a solid arrangement.
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Figure 6d. Paraaortic lymph node metastasis from an undetected RCC in a 55-year-old woman with left flank pain. (a) Contrast-enhanced helical CT scan shows an enlarged left paraaortic lymph node (arrow) and a normal left kidney. Surgery was performed to remove the enlarged lymph node and also demonstrated a normal left kidney. (b) Photomicrograph (original magnification, x40; hematoxylineosin stain) of the surgically removed left paraaortic lymph node shows renal carcinoma cells. (c) Contrast-enhanced turbo spin-echo T1-weighted MR image (536/11) obtained 6 months after initial imaging work-up shows a normal-appearing left kidney. (d) Contrast-enhanced helical CT scan obtained 3 years after initial imaging work-up shows a well-defined, enhancing mass (M) with soft-tissue attenuation occupying the medial aspect of the left kidney and causing mild hydronephrosis. (e) Contrast-enhanced helical CT scan obtained inferior to d 2 weeks later with the patient prone shows the soft-tissue mass (M). CT-guided percutaneous biopsy of the mass was performed. (f) Photomicrograph (original magnification, x40; hematoxylineosin stain) of tissue obtained at CT-guided percutaneous biopsy reveals clear cell renal carcinoma in a solid arrangement.
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Figure 6e. Paraaortic lymph node metastasis from an undetected RCC in a 55-year-old woman with left flank pain. (a) Contrast-enhanced helical CT scan shows an enlarged left paraaortic lymph node (arrow) and a normal left kidney. Surgery was performed to remove the enlarged lymph node and also demonstrated a normal left kidney. (b) Photomicrograph (original magnification, x40; hematoxylineosin stain) of the surgically removed left paraaortic lymph node shows renal carcinoma cells. (c) Contrast-enhanced turbo spin-echo T1-weighted MR image (536/11) obtained 6 months after initial imaging work-up shows a normal-appearing left kidney. (d) Contrast-enhanced helical CT scan obtained 3 years after initial imaging work-up shows a well-defined, enhancing mass (M) with soft-tissue attenuation occupying the medial aspect of the left kidney and causing mild hydronephrosis. (e) Contrast-enhanced helical CT scan obtained inferior to d 2 weeks later with the patient prone shows the soft-tissue mass (M). CT-guided percutaneous biopsy of the mass was performed. (f) Photomicrograph (original magnification, x40; hematoxylineosin stain) of tissue obtained at CT-guided percutaneous biopsy reveals clear cell renal carcinoma in a solid arrangement.
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Figure 6f. Paraaortic lymph node metastasis from an undetected RCC in a 55-year-old woman with left flank pain. (a) Contrast-enhanced helical CT scan shows an enlarged left paraaortic lymph node (arrow) and a normal left kidney. Surgery was performed to remove the enlarged lymph node and also demonstrated a normal left kidney. (b) Photomicrograph (original magnification, x40; hematoxylineosin stain) of the surgically removed left paraaortic lymph node shows renal carcinoma cells. (c) Contrast-enhanced turbo spin-echo T1-weighted MR image (536/11) obtained 6 months after initial imaging work-up shows a normal-appearing left kidney. (d) Contrast-enhanced helical CT scan obtained 3 years after initial imaging work-up shows a well-defined, enhancing mass (M) with soft-tissue attenuation occupying the medial aspect of the left kidney and causing mild hydronephrosis. (e) Contrast-enhanced helical CT scan obtained inferior to d 2 weeks later with the patient prone shows the soft-tissue mass (M). CT-guided percutaneous biopsy of the mass was performed. (f) Photomicrograph (original magnification, x40; hematoxylineosin stain) of tissue obtained at CT-guided percutaneous biopsy reveals clear cell renal carcinoma in a solid arrangement.
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RCC Causing a Large Arteriovenous Fistula
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The angiographic characteristics of hypervascular RCCs include the presence of tumor vessels, pooling of contrast material within abnormal vessels, prolonged staining of the neoplasm, avascular areas due to necrosis or hemorrhage, and arteriovenous communications. These arteriovenous communications may lead to early enhancement of the renal vein and inferior vena cava (IVC). Occasionally, such fistulas are large enough to cause high-output congestive heart failure (1). A large arteriovenous fistula within an RCC has been demonstrated at CT and MR imaging in only a few patients (23,24). With this phenomenon, the solid components of the tumor may be hidden by the vascular communication. Affected patients usually present with cardiac failure, an abdominal bruit, or renal hypertension. Both of the patients in our study with arteriovenous fistulas presented with hypertension, gross hematuria, and extrinsic indentation caused by collateral vessels in the upper portion of the left ureter (Fig 7).
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Figure 7a. (a) Drawing illustrates a large arteriovenous (A-V) fistula within a renal tumor. The fistula is associated with intense venous flow to the left renal vein and periureteral veins that causes ureteral notching. (b–f) Large arteriovenous fistula caused by RCC in an 80-year-old woman with gross hematuria. (b) Intravenous urogram shows left ureteral notching (arrows) as the only abnormal finding. (c–e) Axial fast spin-echo T2-weighted MR images (10,000/132) show a 4-cm heterogeneous, predominantly hypointense solid mass (M) in the upper pole of the left kidney associated with large, tortuous tubular structures (arrow in d and e) that demonstrate no signal intensity. (f) Coronal fast spin-echo T2-weighted MR image (2900/155) demonstrates enlarged, tortuous veins (arrows) originating from the tumor and coursing toward the renal veins and periureteral region.
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Figure 7b. (a) Drawing illustrates a large arteriovenous (A-V) fistula within a renal tumor. The fistula is associated with intense venous flow to the left renal vein and periureteral veins that causes ureteral notching. (b–f) Large arteriovenous fistula caused by RCC in an 80-year-old woman with gross hematuria. (b) Intravenous urogram shows left ureteral notching (arrows) as the only abnormal finding. (c–e) Axial fast spin-echo T2-weighted MR images (10,000/132) show a 4-cm heterogeneous, predominantly hypointense solid mass (M) in the upper pole of the left kidney associated with large, tortuous tubular structures (arrow in d and e) that demonstrate no signal intensity. (f) Coronal fast spin-echo T2-weighted MR image (2900/155) demonstrates enlarged, tortuous veins (arrows) originating from the tumor and coursing toward the renal veins and periureteral region.
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Figure 7c. (a) Drawing illustrates a large arteriovenous (A-V) fistula within a renal tumor. The fistula is associated with intense venous flow to the left renal vein and periureteral veins that causes ureteral notching. (b–f) Large arteriovenous fistula caused by RCC in an 80-year-old woman with gross hematuria. (b) Intravenous urogram shows left ureteral notching (arrows) as the only abnormal finding. (c–e) Axial fast spin-echo T2-weighted MR images (10,000/132) show a 4-cm heterogeneous, predominantly hypointense solid mass (M) in the upper pole of the left kidney associated with large, tortuous tubular structures (arrow in d and e) that demonstrate no signal intensity. (f) Coronal fast spin-echo T2-weighted MR image (2900/155) demonstrates enlarged, tortuous veins (arrows) originating from the tumor and coursing toward the renal veins and periureteral region.
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Figure 7d. (a) Drawing illustrates a large arteriovenous (A-V) fistula within a renal tumor. The fistula is associated with intense venous flow to the left renal vein and periureteral veins that causes ureteral notching. (b–f) Large arteriovenous fistula caused by RCC in an 80-year-old woman with gross hematuria. (b) Intravenous urogram shows left ureteral notching (arrows) as the only abnormal finding. (c–e) Axial fast spin-echo T2-weighted MR images (10,000/132) show a 4-cm heterogeneous, predominantly hypointense solid mass (M) in the upper pole of the left kidney associated with large, tortuous tubular structures (arrow in d and e) that demonstrate no signal intensity. (f) Coronal fast spin-echo T2-weighted MR image (2900/155) demonstrates enlarged, tortuous veins (arrows) originating from the tumor and coursing toward the renal veins and periureteral region.
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Figure 7e. (a) Drawing illustrates a large arteriovenous (A-V) fistula within a renal tumor. The fistula is associated with intense venous flow to the left renal vein and periureteral veins that causes ureteral notching. (b–f) Large arteriovenous fistula caused by RCC in an 80-year-old woman with gross hematuria. (b) Intravenous urogram shows left ureteral notching (arrows) as the only abnormal finding. (c–e) Axial fast spin-echo T2-weighted MR images (10,000/132) show a 4-cm heterogeneous, predominantly hypointense solid mass (M) in the upper pole of the left kidney associated with large, tortuous tubular structures (arrow in d and e) that demonstrate no signal intensity. (f) Coronal fast spin-echo T2-weighted MR image (2900/155) demonstrates enlarged, tortuous veins (arrows) originating from the tumor and coursing toward the renal veins and periureteral region.
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Figure 7f. (a) Drawing illustrates a large arteriovenous (A-V) fistula within a renal tumor. The fistula is associated with intense venous flow to the left renal vein and periureteral veins that causes ureteral notching. (b–f) Large arteriovenous fistula caused by RCC in an 80-year-old woman with gross hematuria. (b) Intravenous urogram shows left ureteral notching (arrows) as the only abnormal finding. (c–e) Axial fast spin-echo T2-weighted MR images (10,000/132) show a 4-cm heterogeneous, predominantly hypointense solid mass (M) in the upper pole of the left kidney associated with large, tortuous tubular structures (arrow in d and e) that demonstrate no signal intensity. (f) Coronal fast spin-echo T2-weighted MR image (2900/155) demonstrates enlarged, tortuous veins (arrows) originating from the tumor and coursing toward the renal veins and periureteral region.
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Spontaneous Perirenal Hematoma
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According to a study by Zhang et al (25), the most common causes of spontaneous unilateral perirenal hemorrhage are benign or malignant neoplasms (61% of cases), with angiomyolipoma (AML) being the most common neoplasm, followed closely by RCC. These tumors vary from 1 to 20 cm in diameter. Renal AML more than 4 cm in diameter has a greater tendency to bleed spontaneously. For RCC, tumor size is not a good indicator of bleeding risk, since tumors less than 4 cm are nearly as likely to bleed as larger tumors (25). CT has the greatest sensitivity (100%) for the presence of perirenal hemorrhage but has a lower sensitivity for detection of the underlying cause. When CT is contraindicated (eg, in patients with contrast material sensitivity or renal insufficiency), MR imaging may be useful, especially for follow-up after improvement in the acute hemorrhage. Angiography is particularly useful in cases of bilateral renal hemorrhage, since renal vasculitis (polyarteritis nodosa) is the most common cause of this condition. In cases of unilateral spontaneous hemorrhage, angiography may help identify arteriovenous communications or renal artery aneurysms; occasionally, it may reveal a renal tumor obscured by hemorrhage. When the initial imaging examination does not demonstrate the cause of renal hemorrhage, repeat imaging following resolution or evacuation of the hematoma is essential (Fig 8). This repeat imaging is important if unnecessary nephrectomy is to be avoided, although nephrectomy is performed in about 70% of patients (25). Even if a patient undergoes imaging with multiple modalities both before and after evacuation of the hematoma, the tumor causing the hemorrhage may be too small to be visualized at CT or angiography. This finding was observed in one patient in our series in whom initial imaging (performed both before and after evacuation of the hematoma) did not show any abnormalities. The patient returned 1 year later with hematuria, and follow-up imaging demonstrated a small, lower-pole RCC. In past years, some authors have recommended that radical nephrectomy be performed in all patients with spontaneous renal hemorrhage in whom nonneoplastic causes have been excluded (26). Nowadays, however, multiphasic helical CT and rapid MR imaging sequences have greatly reduced the need for exploratory surgery in the diagnosis and treatment of this condition.
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Figure 8a. Spontaneous perirenal hematoma in a 37-year-old man with sudden left flank pain. (a) Contrast-enhanced CT scan shows a large, relatively hyperattenuating subcapsular-perirenal fluid collection representing hematoma (H) with no evidence of underlying disease. (b) Selective left renal angiogram obtained before surgical evacuation of the hematoma reveals only parenchymal deformity (arrows). (c) Follow-up US image obtained 18 months later demonstrates a small, echogenic, exophytic solid mass (arrows) at the lower pole of the left kidney.
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Figure 8b. Spontaneous perirenal hematoma in a 37-year-old man with sudden left flank pain. (a) Contrast-enhanced CT scan shows a large, relatively hyperattenuating subcapsular-perirenal fluid collection representing hematoma (H) with no evidence of underlying disease. (b) Selective left renal angiogram obtained before surgical evacuation of the hematoma reveals only parenchymal deformity (arrows). (c) Follow-up US image obtained 18 months later demonstrates a small, echogenic, exophytic solid mass (arrows) at the lower pole of the left kidney.
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Figure 8c. Spontaneous perirenal hematoma in a 37-year-old man with sudden left flank pain. (a) Contrast-enhanced CT scan shows a large, relatively hyperattenuating subcapsular-perirenal fluid collection representing hematoma (H) with no evidence of underlying disease. (b) Selective left renal angiogram obtained before surgical evacuation of the hematoma reveals only parenchymal deformity (arrows). (c) Follow-up US image obtained 18 months later demonstrates a small, echogenic, exophytic solid mass (arrows) at the lower pole of the left kidney.
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RCC Engulfing Perirenal Fat
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In the absence of compelling imaging or clinical indicators to the contrary, the presence of fat in a renal lesion (from –20 to –120 HU on CT scans) is, for all practical purposes, diagnostic for AML and usually does not require follow-up or surgery (unless greater than 4 cm, in view of the risk of hemorrhage from larger AMLs). However, sporadic cases of RCC with macroscopic evidence of fat have been reported (27–31). Four distinct mechanisms have been suggested to explain this unusual feature (27–31). The first mechanism is osseous metaplasia of the nonepithelial stromal portion of the tumor with growth of fatty marrow elements among the bone trabeculae. The combination of fat and calcification should suggest the diagnosis of a malignant tumor because calcification is not usually present in AML (30). A second mechanism is the presence of cholesterol clefts and lipid vacuoles in areas of tumor lipid necrosis, as was recently seen in three patients with RCCs that contained intratumoral fat without evidence of calcifications at CT (31, 32). A third mechanism is the development of a distinct nodule of mature, well-circumscribed adipose tissue within an encapsulated, noncalcified papillary RCC (33). A fourth mechanism is the engulfment of perirenal or sinus fat by a large, exophytic and infiltrative tumor (Fig 9) (27).
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Figure 9a. RCC engulfing perirenal fat and simulating an exophytic AML in a 62-year-old woman with weight loss and right flank pain. Contrast-enhanced CT scans obtained at the top (a) and upper pole (b) of the right kidney show a large, heterogeneously enhancing mass (M) with soft-tissue attenuation arising from the lateral aspect of the upper pole and extending into the peri-renal space. Several areas of fat (arrow) are seen within the tumor (region of interest [cursor] = – 93 HU). (Reprinted, with permission, from reference 27.)
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Figure 9b. RCC engulfing perirenal fat and simulating an exophytic AML in a 62-year-old woman with weight loss and right flank pain. Contrast-enhanced CT scans obtained at the top (a) and upper pole (b) of the right kidney show a large, heterogeneously enhancing mass (M) with soft-tissue attenuation arising from the lateral aspect of the upper pole and extending into the peri-renal space. Several areas of fat (arrow) are seen within the tumor (region of interest [cursor] = – 93 HU). (Reprinted, with permission, from reference 27.)
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Transparenchymal Renal Propagation of RCC and Renal Vein Thrombosis
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RCC has an expansive growth pattern. Superficial tumors ultimately displace or invade the renal capsule, whereas deeper tumors often extend toward the renal sinus and may invade the pelvocaliceal system. Function in a cancerous kidney may be diminished or absent in the presence of replacement of the parenchyma or invasion of the collecting system or renal vein. To our knowledge, transparenchymal renal propagation from a lower-pole RCC to the upper pole has not been described in the literature. This phenomenon was observed in only one patient in our series. The propagation occurred through the renal cortex, sparing the medulla, but was associated with (a) invasion of the left renal vein and IVC and (b) extensive collateral venous circulation that caused notching of the left ureter (Figs 10, 11).
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Figure 10. Transparenchymal renal propagation of cancer and renal vein thrombosis resulting in a nonfunctioning kidney. Drawing illustrates intrarenal propagation of a lower-pole RCC to the upper pole. Note the presence of "tumor vessels" within the renal vein thrombus, invasion of the IVC, and extensive collateral venous circulation.
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Figure 11a. Transparenchymal renal propagation of cancer and renal vein thrombosis resulting in a nonfunctioning left kidney in a 47-year-old man. The patient had previously undergone surgery for a left-sided varicocele. (a) Retrograde pyelogram shows only stretching of the pelvocaliceal system. (b) Prone longitudinal US image of the left kidney obtained with a 3.5-MHz transducer and a static articulated arm unit reveals an exophytic, hypoechoic solid mass (M) associated with unusual diffuse hypoechogenicity of the renal parenchyma (*). (c) Sagittal US image demonstrates a thrombus (arrows) within the IVC. (d) Venous phase angiogram demonstrates "tumor vessels" in the lower pole of the left kidney (arrowheads) and within the renal vein thrombus (arrow). (e) Photograph of the gross specimen demonstrates the primary tumor (T), an RCC, at the lower pole of the kidney, with transparenchymal renal propagation through the renal cortex, sparing the renal medullae (*).
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Figure 11b. Transparenchymal renal propagation of cancer and renal vein thrombosis resulting in a nonfunctioning left kidney in a 47-year-old man. The patient had previously undergone surgery for a left-sided varicocele. (a) Retrograde pyelogram shows only stretching of the pelvocaliceal system. (b) Prone longitudinal US image of the left kidney obtained with a 3.5-MHz transducer and a static articulated arm unit reveals an exophytic, hypoechoic solid mass (M) associated with unusual diffuse hypoechogenicity of the renal parenchyma (*). (c) Sagittal US image demonstrates a thrombus (arrows) within the IVC. (d) Venous phase angiogram demonstrates "tumor vessels" in the lower pole of the left kidney (arrowheads) and within the renal vein thrombus (arrow). (e) Photograph of the gross specimen demonstrates the primary tumor (T), an RCC, at the lower pole of the kidney, with transparenchymal renal propagation through the renal cortex, sparing the renal medullae (*).
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Figure 11c. Transparenchymal renal propagation of cancer and renal vein thrombosis resulting in a nonfunctioning left kidney in a 47-year-old man. The patient had previously undergone surgery for a left-sided varicocele. (a) Retrograde pyelogram shows only stretching of the pelvocaliceal system. (b) Prone longitudinal US image of the left kidney obtained with a 3.5-MHz transducer and a static articulated arm unit reveals an exophytic, hypoechoic solid mass (M) associated with unusual diffuse hypoechogenicity of the renal parenchyma (*). (c) Sagittal US image demonstrates a thrombus (arrows) within the IVC. (d) Venous phase angiogram demonstrates "tumor vessels" in the lower pole of the left kidney (arrowheads) and within the renal vein thrombus (arrow). (e) Photograph of the gross specimen demonstrates the primary tumor (T), an RCC, at the lower pole of the kidney, with transparenchymal renal propagation through the renal cortex, sparing the renal medullae (*).
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Figure 11d. Transparenchymal renal propagation of cancer and renal vein thrombosis resulting in a nonfunctioning left kidney in a 47-year-old man. The patient had previously undergone surgery for a left-sided varicocele. (a) Retrograde pyelogram shows only stretching of the pelvocaliceal system. (b) Prone longitudinal US image of the left kidney obtained with a 3.5-MHz transducer and a static articulated arm unit reveals an exophytic, hypoechoic solid mass (M) associated with unusual diffuse hypoechogenicity of the renal parenchyma (*). (c) Sagittal US image demonstrates a thrombus (arrows) within the IVC. (d) Venous phase angiogram demonstrates "tumor vessels" in the lower pole of the left kidney (arrowheads) and within the renal vein thrombus (arrow). (e) Photograph of the gross specimen demonstrates the primary tumor (T), an RCC, at the lower pole of the kidney, with transparenchymal renal propagation through the renal cortex, sparing the renal medullae (*).
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Figure 11e. Transparenchymal renal propagation of cancer and renal vein thrombosis resulting in a nonfunctioning left kidney in a 47-year-old man. The patient had previously undergone surgery for a left-sided varicocele. (a) Retrograde pyelogram shows only stretching of the pelvocaliceal system. (b) Prone longitudinal US image of the left kidney obtained with a 3.5-MHz transducer and a static articulated arm unit reveals an exophytic, hypoechoic solid mass (M) associated with unusual diffuse hypoechogenicity of the renal parenchyma (*). (c) Sagittal US image demonstrates a thrombus (arrows) within the IVC. (d) Venous phase angiogram demonstrates "tumor vessels" in the lower pole of the left kidney (arrowheads) and within the renal vein thrombus (arrow). (e) Photograph of the gross specimen demonstrates the primary tumor (T), an RCC, at the lower pole of the kidney, with transparenchymal renal propagation through the renal cortex, sparing the renal medullae (*).
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Conclusions
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RCC is at times characterized by unusual radiologic features. For example, the radiologist should be aware of the possibility of tumor multifocality or adrenal metastases from a high-grade small renal tumor, as well as of the association of RCC with lymphoma. He or she should also be aware of the importance of following up a multiseptated cystic mass found at US or a Bosniak category IIF renal cyst, since these lesions can be an early manifestation of cystic carcinoma. Occasionally, other rare imaging manifestations of RCC may occur, such as an arteriovenous communication within the tumor or retroperitoneal lymph node metastases as the first sign of an undetectable renal cancer. Familiarity with the unusual radiologic features of RCC described in this article helps in making the correct diagnosis as well as in developing, in specific situations, an appropriate follow-up and treatment strategy.
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Footnotes
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Abbreviations: AML = angiomyolipoma, IVC = inferior vena cava, RCC = renal cell carcinoma
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References
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Abstract
LEARNING OBJECTIVES
