Metabolic parameters analysis of 18F-FDG PET/CT in the diagnosis and differential diagnosis of collecting duct carcinoma

PURPOSE

This study aims to explore the diagnostic performance of 18F-FDG PET/CT in distinguishing collecting duct carcinoma (CDC) from clear cell renal cell carcinoma (ccRCC).

METHODS

A retrospective analysis was conducted on 11 patients with CDC and 27 patients with ccRCC who underwent 18F-FDG PET/CT examinations. Clinical indicators and the SUVmax, tumor-to-liver standardized uptake value ratio (TLR), tumor-to-kidney standardized uptake value ratio (TKR), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) values of the primary tumor, whole-body MTV (WBMTV), and whole-body TLG (WBTLG) based on a baseline PET scan, were recorded and compared between the two groups. To assess the discriminative power of these metabolic parameters between CDC and ccRCC, we performed a receiver operating characteristic (ROC) curve analysis.

RESULTS

The median age of the 11 CDC patients was 59 years. All CDC patients were in advanced stages (18% stage III and 82% stage IV). Compare with ccRCC patients, CDC patients had higher lymph node metastases rates (72.7% vs. 22.2%, P = 0.008) and distant metastases rates (81.8% vs. 22.2%, P = 0.001). The primary tumor in CDC also showed higher SUVmax (10.5 vs. 4.0, P < 0.001), TLR (3.9 vs. 1.4, P < 0.001), TKR (4.4 vs. 1.5, P < 0.001), MTV (53.2 vs. 9.5, P = 0.021), and TLG (305.7 vs. 30.4, P = 0.0069) than ccRCC. The WBMTV and WBTLG of CDC patients were also higher than the ccRCC group (144.1 vs. 9.5, P = 0.0013 and 528.4 vs. 30.4, P = 0.0013, respectively). ROC curve analysis revealed no significant differences in the ability of SUVmax, TLR and TKR to differentiate CDC from ccRCC. Median survival for CDC was 36 months, worse for older patients.

CONCLUSION

The utilization of 18F-FDG PET/CT can assist to detect the metastases and provide guidance for diagnosis and staging. Metabolic parameters obtained from 18F-FDG PET/CT hold promise for distinguishing CDC from ccRCC.

Predominantly multiple focal non-cystic renal lesions: an imaging approach

Multiple non-cystic renal lesions are occasionally discovered during imaging for various reasons and poses a diagnostic challenge to the practicing radiologist. These lesions may appear as a primary or dominant imaging finding or may be an additional abnormality in the setting of multiorgan involvement. Awareness of the imaging appearance of the various entities presenting as renal lesions integrated with associated extrarenal imaging findings along with clinical information is crucial for a proper diagnostic approach and patient work-up. This review summarizes the most relevant causes of infectious, inflammatory, vascular, and neoplastic disorders presenting as predominantly multiple focal non-cystic lesions.

Intriguing Encounter: Unveiling Squamous Cell Carcinoma Lung with Rare Bilateral Renal and Pituitary Metastasis on [18F]-FDG PET/CT

Metastases from squamous cell carcinoma of the lung typically occur in the brain, liver, adrenal glands, bone, and regional lymph nodes. It is exceedingly uncommon to encounter multiple rare sites of metastasis from a single primary neoplasm. Herein, we describe a case of a 44-year-old male diagnosed with squamous cell carcinoma lung with pituitary and renal metastasis detected on 18F-FDG (Fluorodeoxyglucose) PET/CT. 18F-FDG PET/CT is the standard of care and is an integral part of the clinical staging of patients with lung cancer. According to published literature, the incidence of symptomatic pituitary and renal metastasis from squamous cell carcinoma lung is rare to find with incidences <1% and 5%, respectively. The revelation of rare sites of metastasis originating from primary squamous cell carcinoma lung, as reported in this case on FDG PET/CT, illuminates the exceptional rarity and intricacies in oncology. The exquisite sensitivity of FDG PET/CT enables the identification of occult metastasis in atypical anatomical locations, presenting a distinct advantage over conventional imaging modalities.

FDG PET/CT in Solitary Isolated Renal Metastasis From Squamous Cell Lung Cancer

ABSTRACT

We describe FDG PET/CT findings in a patient with a solitary isolated renal metastasis from squamous cell lung cancer. The renal metastasis appeared as a small focus of activity at the renal cortex on FDG PET/CT at initial staging of the lung tumor, misinterpreted as cortical tracer retention, and was significantly enlarged on the second FDG PET/CT performed 4 months after the first PET/CT. This case demonstrates the usefulness of FDG PET/CT in identifying unexpected extrathoracic metastasis from lung cancer. Focal FDG uptake in the renal cortical region in a cancer patient should be evaluated carefully to avoid misdiagnosis.

Multimodality imaging of renal lymphoma and its mimics

Lymphomatous involvement of the genitourinary system, particularly the kidneys, is commonly detected on autopsies; yet on conventional diagnostic imaging renal lymphoma is significantly underestimated and underreported, in part due to its variable imaging appearance and overlapping features with other conditions. We present a spectrum of typical and atypical appearances of renal lymphoma using multimodality imaging, while reviewing the roles of imaging in the detection, diagnosis, staging, and surveillance of patients with lymphoma. We also illustrate a breadth of benign and malignant entities with similar imaging features confounding the diagnosis of renal lymphoma, emphasizing the role of percutaneous image-guided biopsy. Understanding the spectrum of appearances of renal lymphoma and recognizing the overlapping entities will help radiologists improve diagnostic confidence and accuracy.

FDG PET/CT in Unilateral Renal Metastasis From Colon Cancer

ABSTRACT

Renal metastasis from colon cancer is rare. We describe FDG PET/CT findings in a case with a right renal and a postcaval lymph node metastasis from colon cancer. Both the renal tumor and postcaval lymph node showed increased FDG uptake with SUVmax of 6.1 for the renal tumor and 5.5 for the postcaval lymph node. The imaging findings mimicked a primary renal cancer with postcaval lymph node metastasis.

Bilateral nephromegaly due to direct leukemic cell invasion in the initial and relapse phases of T-cell acute lymphoblastic leukaemia: A case report

RATIONALE

T-cell acute lymphoblastic leukemia is a relatively uncommon disorder in adults. Kidneys are not frequently invaded by leukemic cells, and patients with adult ALL showing nephromegaly as an initial presentation are rare.

PATIENT CONCERNS

A 54-year-old man was referred to our institution for mild anemia and thrombocytopenia. Laboratory tests showed bicytopenia with abnormal lymphoid cells in the peripheral blood and mild renal dysfunction.

DIAGNOSIS

Ultrasonography and computed tomography (CT) revealed bilateral enlargement of the kidneys. [18F]-fluorodeoxyglucose positron emission tomography/CT demonstrated a strong increase in metabolic uptake in the bilateral kidneys. A kidney biopsy revealed a leukemia invasion into the parenchyma. Based on the lymphocytic repertoire, the patient's condition was diagnosed as T-cell acute lymphoblastic leukaemia.

INTERVENTIONS

The patient received hyper-cyclophosphamide, vincristine, adriamycin, and dexamethasone and high-dose methotrexate and cytarabine as induction chemotherapy. After his leukemia relapsed, he received nelarabine as a second induction therapy and underwent haploidentical peripheral blood stem cell transplantation.

OUTCOMES

Complete remission (CR) was achieved after chemotherapy. Chemotherapy also improved renal function associated with the normalization of bilateral nephromegaly. Repeated [18F]-fluorodeoxyglucose - positron emission tomography/CT posttreatment showedregression of metabolic uptake in the bilateral kidneys. The patient underwent cord blood transplantation at the first CR, but his leukemia relapsed 9 months later. At relapse, bilateral nephromegaly reappeared. Then, the second induction therapy induced CR for at least 10 months after induction therapy.

LESSONS

Although rare, ALL in the initial and relapsed phases can be associated with bilateral nephromegaly and renal impairment due to the invasion of leukemic cells into the parenchyma with or without abnormal leukemic cells in circulation. Leukemia is an important differential diagnosis of renal impairment with bilateral nephromegaly.

FDG-PET/CT Variants and Pitfalls in Haematological Malignancies

Hematologic malignancies represent a vast group of hematopoietic and lymphoid cancers that typically involve the blood, the bone marrow, and the lymphatic organs. Due to extensive research and well defined and standardized response criteria, the role of [¹⁸F]FDG-PET/CT is well defined in these malignancies. Never the less, the reliability of visual and quantitative interpretation of PET/CT may be impaired by several factors including inconsistent scanning protocols and image reconstruction methods. Furthermore, the uptake of [¹⁸F]FDG not only reflects tissue glucose consumption by malignant lesions, but also in other situations such as in inflammatory lesions, local and systemic infections, benign tumors, reactive thymic hyperplasia, histiocytic infiltration, among others; or following granulocyte colony stimulating factors therapy, radiation therapy, chemotherapy or surgical interventions, all of which are a potential source of false-positive or negative interpretations. Therefore it is of paramount importance for the Nuclear Medicine Physician to be familiar with, not only the normal distribution of [¹⁸F]FDG in the body, but also with the most frequent findings that may hamper a correct interpretation of the scan, which could ultimately alter the patients management. In this review, we describe these myriad of situations so the interpreting physician can be familiar with them, providing tools for their correct identification and interpretation when possible.

Rosai-Dorfman disease: A case report of asymptomatic isolated renal involvement

A possible diagnosis of RDD should be kept in mind when encountering a patient with raised plasma creatinine levels and renal mass. Timely diagnosis and management of RDD will help prevent future kidney loss.

Multicentric primary diffuse large B-cell lymphoma in genitourinary tract detected on 18F-F-fluorodeoxyglucose positron emission tomography with computed tomography: An uncommon presentation of a common malignancy

Primary extranodal lymphomas (ENLs) are lymphomas with no or minor nodal involvement and a dominant extranodal component originating from any organ. Primary ENL originating in the genitourinary tract is extremely rare. Diffuse large B-cell lymphoma (DLBCL) is the most frequent histological subtype in primary genitourinary lymphoma. Lymphomatous involvement of genitourinary system organs is common in the setting of disseminated disease. Herein, we present a unique case of primary multicentric extranodal DLBCL of the urogenital system involving ureter, seminal vesicle, and penis detected on 18fluro-deoxyglucose positron emission tomography with computed tomography, and to the best of our knowledge, it is the first case report with multiorgan involvement within a single (urogenital) organ system in a patient without disseminated disease, i.e., with no other nodal or extranodal organ system involvement.

[Intravascular large B cell lymphoma pathological findings led by positron emission tomography findings: About one case]

Intravascular large B cell lymphoma is a rare non-Hodgkin large B cell lymphoma disease, with heterogeneous clinical manifestation and difficult pathological diagnosis. Positron emission tomography may be helpfull in this context and has already been reported. A 45-year-old woman was admitted for persistent high fever, inflammatory syndrome and unexplained haemophagocytic syndrome. Bilateral cortical renal hypermetabolism at positron emission tomography initially misled to pyelonephritis diagnosis and secondarily led to kidney biopsy, which showed intravascular large B cell lymphoma. Renal involvement in intravascular large B cell lymphoma is rare and is usually characterized by acute renal failure and proteinuria. Global hypermetabolism at positron emission tomography has already been described in this context, but cortical hypermetabolism has never been associated with pathological findings. In front of persistent high fever without etiology, this positron emission tomography feature must lead to intravascular large B cell lymphoma suspicion and to kidney biopsy to obtain pathological proof.

Enormous primary renal diffuse large B-cell lymphoma: A case report and literature review

Introduction

Primary renal lymphoma is a rare malignant lymphoma that is difficult to differentiate from renal cell carcinoma. Positron emission tomography/computed tomography and image-guided percutaneous biopsy are valuable tools for diagnosis.

Case report

A 64-year-old woman presented with a 2-year history of repeated right waist pain and a 1-month history of nausea, vomiting, and frequent and urgent urination. A computed tomography scan showed a huge mass that was initially considered to be renal cell carcinoma at the upper pole of the right kidney. The mass had invaded the renal pelvis, narrowed the right renal artery, and constricted the inferior vena cava and liver. Postoperative examination of the tumor confirmed lymphoma. We herein present this case and its multidisciplinary team management.

Conclusion

Multidisciplinary team management is efficient for preoperative assessment and surgery in difficult and high-risk cases. Based on our literature review, we suggest biopsy before chemotherapy whenever possible. Chemotherapy can be implemented after surgery for better survival outcomes.

FDG PET/CT in 2 Cases of Renal Metastasis From Esophageal Squamous Cell Carcinoma

Clinically, renal metastasis from esophageal squamous cell carcinoma is uncommon. We present 2 cases of renal metastasis from esophageal squamous cell carcinoma with enhanced CT and FDG PET/CT findings. In the first case, right kidney and right renal hilum were the only known metastatic sites. In the second case, bilateral kidneys were the only known metastatic sites. All the renal metastatic tumors appeared as hypovascular and hypoattenuating masses involving both the renal cortex and medulla on enhanced CT and intense FDG uptake on FDG PET/CT.

Estimation of kidneys and urinary bladder doses based on the region of interest in 18fluorine-fluorodeoxyglucose positron emission tomography/computed tomography examination: a preliminary study

BACKGROUND

Kidneys and urinary bladder are common physiologic uptake sites of 18fluorine-fluorodeoxyglucose (¹⁸F-FDG) causing increased exposure of low energy ionizing radiation to these organs. Accurate measurement of organ dose is vital as ¹⁸F-FDG is directly exposed to the organs. Organ dose from ¹⁸F-FDG PET is calculated according to the injected ¹⁸F-FDG activity with the application of dose coefficients established by International Commission on Radiological Protection (ICRP). But this dose calculation technique is not directly measured from these organs; rather it is calculated based on total injected activity of radiotracer prior to scanning. This study estimated the ¹⁸F-FDG dose to the kidneys and urinary bladder in whole body positron emission tomography/computed tomography (PET/CT) examination by comparing dose from total injected activity of ¹⁸F-FDG (calculated dose) and dose from organs activity based on the region of interest (ROI) (measured dose).

METHODS

Nine subjects were injected intravenously with the mean ¹⁸F-FDG dose of 292.42 MBq prior to whole body PET/CT scanning. Kidneys and urinary bladder doses were estimated by using two approaches which are the total injected activity of ¹⁸F-FDG and organs activity concentration of ¹⁸F-FDG based on drawn ROI with the application of recommended dose coefficients for ¹⁸F-FDG described in the ICRP 80 and ICRP 106.

RESULTS

The mean percentage difference between calculated dose and measured dose ranged from 98.95% to 99.29% for the kidneys based on ICRP 80 and 98.96% to 99.32% based on ICRP 106. Whilst, the mean percentage difference between calculated dose and measured dose was 97.08% and 97.27% for urinary bladder based on ICRP 80 while 96.99% and 97.28% based on ICRP 106. Whereas, the range of mean percentage difference between calculated and measured organ doses derived from ICRP 106 and ICRP 80 for kidney doses were from 17.00% to 40.00% and for urinary bladder dose was 18.46% to 18.75%.

CONCLUSIONS

There is a significant difference between calculated dose and measured dose. The use of organ activity estimation based on drawn ROI and the latest version of ICRP 106 dose coefficient should be explored deeper to obtain accurate radiation dose to patients.

Imaging of Extranodal Genitourinary Lymphoma

The genitourinary (GU) system is commonly affected by disseminated lymphoma. Rarely, lymphoma can originate from and remain localized to one of the GU organs and thus presents as primary extranodal disease. Up to 40% of lymphomas present as extranodal disease, with only 3% having the GU system as the primary site of involvement. This article describes and correlates the radiologic and pathologic features of extranodal lymphomatous disease affecting the GU system with specific focus on the kidneys, adrenal glands, testicles, and ovaries. Lymphoma of the uterine body and cervix, external female genitalia, urinary bladder, and prostate gland is briefly discussed.

Renal Masses Detected on FDG PET/CT in Patients With Lymphoma: Imaging Features Differentiating Primary Renal Cell Carcinomas From Renal Lymphomatous Involvement

OBJECTIVE

The purpose of this study is to analyze the ¹⁸F-FDG PET/CT features of solid renal masses detected in patients with lymphoma and to evaluate the ability of PET/CT to differentiate renal cell carcinoma (RCC) from renal lymphomatous involvement.

MATERIALS AND METHODS

Thirty-six patients with solid renal masses on PET/CT performed for staging or follow-up of lymphoma were evaluated retrospectively. The features recorded for each renal mass included the following standardized uptake values (SUVs) on PET/CT: the maximum SUV (SUV_max), the mean SUV (SUV_mean), the ratio of the SUV_max of the tumor to that of the normal kidney cortex, the ratio of the SUV_mean of the tumor to that of the normal kidney cortex, the ratio of the SUV_max of the tumor to that of the normal liver, and the ratio of the SUVmean of the tumor to that of the normal liver. Renal mass size and margins (well defined vs infiltrative) and the presence of calcifications were evaluated on CT. Renal biopsy results were used as the reference standard. Relationships between imaging parameters and histopathologic findings were assessed.

RESULTS

Of the 36 renal masses evaluated, 22 (61.1%) were RCCs and 14 (38.9%) were renal lymphomas. All SUV metrics were higher for renal lymphomas than for RCCs (p < 0.0001, for all). All renal lymphomas had an SUV_max higher than 5.98 g/mL (median, 10.99 g/mL), whereas all RCCs had an SUV_max lower than 5.26 g/mL (median, 2.91 g/mL). No statistically significant differences in mass size or margins were found between RCCs and renal lymphoma.

CONCLUSION

PET/CT features may be useful for differentiating RCCs from renal involvement in patients with lymphoma with solid renal masses.

Role of multimodality imaging in the diagnosis of lymphoproliferative malignancies and hematologic disorders of the kidneys

Lymphoproliferative and hematologic disorders of the kidney may present with focal or diffuse renal parenchymal involvement in clinical practice. Radiologic findings of lymphoproliferative and hematologic disorders of the kidney may mimick primary neoplastic and inflammatory disorders of the kidney. All cross-sectional imaging modalities including ultrasonography, computed tomography, and magnetic resonance imaging may be used in the diagnosis of these diseases. Percutaneous biopsy may be used in problematic cases for definitive diagnosis.

Renal Intravascular Large B-cell Lymphoma: A Case Report and Review of the Literature

We herein report the case of a 52-year-old woman who consulted us because of a 2-month history of a fever, anorexia and weight loss. A physical examination was unremarkable. The blood count showed mild anemia and lymphopenia, and lactate dehydrogenase was elevated. Creatinine clearance was normal and proteinuria was undetectable. CT showed enlarged kidneys. A bone marrow biopsy was normal. PET-CT showed an intense uptake of ¹⁸fluorodeoxyglucose in both kidneys. A kidney biopsy provided the diagnosis of intravascular large B-cell lymphoma (IVLBCL). Kidney-limited IVLBCL without an impairment in the renal function or proteinuria has not been described. We analyzed the 38 published cases of IVLBCL involving the kidney to describe the main features of this entity.

Enhanced MRI and 18F-FDG PET/CT Findings of Preoperative Primary Renal Collecting Duct Carcinoma

Primary renal collecting duct carcinoma is an extremely rare neoplasm. We present a case of preoperative collecting duct carcinoma with enhanced MRI and F-FDG PET/CT findings. The MRI and PET imaging showed a round mass in the left kidney, as well as multiple retroperitoneal lesions with slight enhancement and intense FDG uptake, respectively. A left radical nephrectomy was performed. Primary renal collecting duct carcinoma and retroperitoneal lymph node metastases were confirmed histopathologically.

Imaging Manifestations of Hematologic Diseases with Renal and Perinephric Involvement

The kidneys and perinephric tissues can be affected by a variety of hematologic disorders, which usually occur in the setting of multisystem involvement. In many of these disorders, imaging is used to evaluate the extent of disease, guide biopsy, and/or monitor disease activity and patient response to therapy. Lymphoma, leukemia, and multiple myeloma commonly manifest as multiple parenchymal or perinephric lesions. Erdheim-Chester disease and Rosai-Dorfman disease, rare forms of multisystemic histiocytosis, are often identified as perinephric and periureteral masses. Renal abnormalities depicted at imaging in patients with sickle cell disease include renal enlargement, papillary necrosis, and renal medullary carcinoma. Sickle cell disease, along with other causes of intravascular hemolysis, can also lead to hemosiderosis of the renal cortex. Thrombosis of renal veins is sometimes seen in patients with coagulation disorders but more often occurs in association with certain malignancies and nephrotic syndrome. Immunoglobulin G4-related sclerosing disease is another multisystem process that often produces focal renal lesions, seen along with involvement of more characteristic organs such as the pancreas. Perinephric lesions with calcifications should raise the possibility of secondary amyloidosis, especially in patients with a history of lymphoma and multiple myeloma. Although the imaging patterns of renal and perinephric involvement are usually not specific for a single entity, and the same entity can manifest with different or overlapping patterns, familiarity with these patterns and key clinical and histopathologic features may help to narrow the differential diagnosis and determine the next step of care. (©)RSNA, 2016.

Non-Hodgkin lymphoma dominated by multiple organ extranodal disease revealed on FDG PET/CT

The definition of primary extranodal lymphoma is rather controversial and often complicated by the variety of lymphoma types. Here we describe FDG PET/CT findings in 3 pediatric patients with diffuse large B-cell non-Hodgkin lymphomas dominated by extranodal lesions involving multiple organs. Lymphomas arising primarily in extranodal sites can present significant diagnostic challenges due to their morphological diversity and lack of uniformity in histopathological classification.

Mucosa-associated lymphoid tissue lymphoma involving the kidney: a case report and review of the literature

Mucosa-associated lymphoid tissue (MALT) lymphomas arise from various anatomic sites, mostly observed in the gastrointestinal tract; however, involvement of the kidney is extremely rare. We report a case of MALT lymphoma involving the kidney in a 70-year-old man. Radical nephrectomy was performed under the diagnosis of renal cell carcinoma preoperatively. However, the renal specimen showed that the diffuse small- to medium-sized lymphocytes were scattered and formed colonies, and the neoplastic lymphoid cells were positive for CD20, CD79α, and Bcl-2, but negative for CD10 and Cyclin D1; therefore, the final histological diagnosis was MALT lymphoma involving the renal pelvis. Although he was referred to the department of hematology, no additional treatment was given postoperatively, and he has survived for 4 months without evidence of a recurrence of lymphoma at the last follow-up. To the best of our knowledge, to date 37 reports of MALT lymphoma involving the kidney have been published in the literature. We report a case of MALT lymphoma involving the kidney, and review the existing literature.

Molecular imaging of urogenital diseases

There is an expanding and exciting repertoire of PET imaging radiotracers for urogenital diseases, particularly in prostate cancer, renal cell cancer, and renal function. Prostate cancer is the most commonly diagnosed cancer in men. With growing therapeutic options for the treatment of metastatic and advanced prostate cancer, improved functional imaging of prostate cancer beyond the limitations of conventional CT and bone scan is becoming increasingly important for both clinical management and drug development. PET radiotracers, apart from ¹⁸F-FDG, for prostate cancer are ¹⁸F-sodium fluoride, ¹¹C-choline, and ¹⁸F-fluorocholine, and (¹¹C-acetate. Other emerging and promising PET radiotracers include a synthetic l-leucine amino acid analogue (anti-¹⁸F-fluorocyclobutane-1-carboxylic acid), dihydrotestosterone analogue (¹⁸F-fluoro-5α-dihydrotestosterone), and prostate-specific membrane antigen-based PET radiotracers (eg, N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-4-¹⁸F-fluorobenzyl-l-cysteine, ⁸⁹Zr-DFO-J591, and ⁶⁸Ga [HBED-CC]). Larger prospective and comparison trials of these PET radiotracers are needed to establish the role of PET/CT in prostate cancer. Although renal cell cancer imaging with FDG-PET/CT is available, it can be limited, especially for detection of the primary tumor. Improved renal cell cancer detection with carbonic anhydrase IX (CAIX)-based antibody (¹²⁴I-girentuximab) and radioimmunotherapy targeting with ¹⁷⁷Lu-cG250 appear promising. Evaluation of renal injury by imaging renal perfusion and function with novel PET radiotracers include p-¹⁸F-fluorohippurate, hippurate m-cyano-p-¹⁸F-fluorohippurate, and rubidium-82 chloride (typically used for myocardial perfusion imaging). Renal receptor imaging of the renal renin-angiotensin system with a variety of selective PET radioligands is also becoming available for clinical translation.

Imaging of primary and secondary renal lymphoma

OBJECTIVE

This article reviews the CT and MRI patterns of primary and secondary renal lymphomas and discusses the role of percutaneous biopsy in diagnosis and management.

CONCLUSION

Renal lymphoma has a variable imaging spectrum and may mimic renal cell carcinoma. An awareness of the typical and atypical imaging features of both primary and secondary renal lymphomas can help the radiologist to suggest these diagnoses and recommend biopsy when appropriate.