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Prasad et al.Benign Renal Neoplasms

G e n i t o u r i n a r y I m ag i n g • R ev i ew

Benign Renal Neoplasms in Adults: Cross-Sectional Imaging Findings

Srinivasa R. Prasad1

Venkateswar R. Surabhi1

Christine O. Menias2

Abhijit A. Raut3

Kedar N. Chintapalli1

Prasad SR, Surabhi VR, Menias CO, Raut AA, Chintapalli KN

Keywords: benign tumors, CT, kidney, MRI, renal neoplasms, sonography

DOI:10.2214/AJR.07.2724

Received June 13, 2007; accepted after revision July 16, 2007.

1Department of Radiology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229. Address correspondence to S. R. Prasad ([email protected]).

2Department of Radiology, Mallinckrodt Institute of Radiology, St. Louis, MO.

3Department of Radiology, King Edward Memorial Hospital, Mumbai, India.

CMEThis article is available for CME credit. See www.arrs.org for more information.

OBJECTIVE. A broad spectrum of benign renal neoplasms in adults shows characteristicontogeny, histology, and tumor biology. Benign renal tumors are classified into renal cell tu-mors, metanephric tumors, mesenchymal tumors, and mixed epithelial and mesenchymal tu-mors. Select benign tumors show characteristic anatomic distribution and imaging features.However, because of overlapping of findings between benign and malignant renal tumors, his-tologic evaluation may be required to establish a definitive diagnosis. Accurate preoperativecharacterization facilitates optimal patient management.

CONCLUSION. We attempt to provide a comprehensive, contemporary review of benignrenal neoplasms that occur in adults, focusing on cross-sectional imaging characteristics.

enign renal neoplasms that occurin adults constitute a heteroge-neous group of tumors with char-acteristic histology and variable

clinicobiologic profiles. The 2004 WorldHealth Organization (WHO) classificationschemata categorizes benign renal neoplasmson the basis of histogenesis (cell of origin)and histopathology [1] (Appendix 1). Renalneoplasms are thus classified into renal cell,metanephric, mesenchymal, and mixed epi-thelial and mesenchymal tumors.

Recent advances in imaging technologyhave resulted in the detection of incidental renalmasses in seemingly asymptomatic patients.Although renal cell carcinoma (RCC) is by farthe most lethal urologic malignancy, benign tu-mors constitute a significant proportion ofmasses in patients who undergo surgery. In a re-cent study of 143 patients with presumed soli-tary RCC, the authors found 16.1% of patientswho underwent partial nephrectomy had be-nign masses [2]. Other studies have also foundthat a significant proportion of solid renalmasses are histologically benign [3–5]. Also,percutaneous renal mass biopsy is being in-creasingly performed to preoperatively charac-terize renal masses and to establish definitivediagnoses [3, 4, 6, 7]. Recent advances in histo-pathology, immunocytochemistry, and cytoge-netics assist in fairly accurate characterizationof most renal masses and help guide optimalpatient management [1, 7, 8]. A recent study of66 renal mass biopsies found 98% accuracy and

79% sample adequacy [7]. However, patholo-gists advise caution when interpreting tumors,specifically those with oncocytic features or hy-brid or collision tumors [7, 9]. Laparoscopicpartial nephrectomies and percutaneous abla-tions are being increasingly performed to treatsmall renal tumors and to establish a definitivediagnosis [10, 11].

Renal Cell NeoplasmsOncocytoma

Oncocytoma is a benign renal cell neoplasmthat accounts for approximately 5% of all adultprimary renal epithelial neoplasms in surgicalseries [1]. Oncocytoma is hypothesized tooriginate from or differentiate toward type Aintercalated cells of the cortical collecting duct[12, 13]. The peak age of incidence is in theseventh decade; men are more likely to be af-fected than women. Most tumors occur spo-radically in asymptomatic patients.

Oncocytoma is histologically composed ofnests and acini of large polygonal cells withmitochondria-rich eosinophilic cytoplasm[1]. Oncocytomas do not show diffuse cyto-plasmic Hale colloidal iron staining, in con-tradistinction to chromophobe RCCs.

Oncocytomas typically appear as solitary,well-demarcated, unencapsulated, fairly ho-mogeneous renal cortical tumors. Bilateral,multicentric oncocytomas are seen in heredi-tary syndromes of renal oncocytosis and Birt-Hogg-Dubé syndrome (in association withthe chromophobe subtype and other RCC

B

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subtypes) [14] (Fig. 1). A characteristic cen-tral stellate fibrotic scar (more often seen withlarge tumors) is seen in up to 33% of tumors[1] (Fig. 2). Hemorrhage may be found in upto 20% of cases. A spoke-wheel pattern offeeding arteries associated with a homoge-neous nephrogram is a characteristic findingon catheter angiography [15]. However, on-cocytomas are indistinguishable from renalcell carcinomas on the basis of imaging find-ings alone. In addition, oncocytomas may beassociated with RCCs either as hybrid tumors(pathologic features of both oncocytomas andchromophobe or other RCC subtypes) or ascollision tumors [9]. Thus, despite advancesin histopathologic techniques (including im-munocytochemistry and cytogenetics), a par-tial nephrectomy may be required for accu-rate characterization [7].

Papillary AdenomaPapillary adenomas are the most common

renal epithelial neoplasms. According to au-topsy series, approximately 40% of patientsolder than 70 years harbor renal adenomas[1]. Papillary adenomas are also commonlyfound in patients with acquired renal cysticdisease and in patients undergoing long-termhemodialysis [16]. A papillary adenoma-to-carcinoma sequence has been described thatis akin to similar transformation in colonicadenomas [17, 18].

By definition, papillary adenomas measure5 mm or less [1]. They are usually subcapsu-lar and solitary. Adenomas are histologicallycharacterized by papillary or tubular cytoar-chitecture and frequent psammoma bodies[1]. Cytogenetic changes of papillary ade-nomas include loss of the Y chromosome andcombined trisomy of chromosomes 7 and 17[19]. Histologic and genetic abnormalities of

renal adenomas are indistinguishable frompapillary RCCs [1, 20].

Papillary adenomas are extremely small(< 5 mm) and may not be distinguished fromother renal tumors (particularly RCC) andpseudotumors on imaging studies.

Metanephric NeoplasmsMetanephric neoplasms are a heteroge-

neous group of benign renal neoplasms thatinclude metanephric adenoma (epithelial tu-mor), metanephric stromal tumor (stromalneoplasm), and metanephric adenofibroma(mixed epithelial and stromal neoplasm) [21].These tumors are histogenetically related toWilms’ tumor and are postulated to representthe most hyperdifferentiated, benign end ofthe nephroblastoma spectrum [21]. Meta-nephric adenofibromas and metanephric stro-mal tumors are essentially pediatric tumorsand will not be discussed in this article.

Metanephric adenoma is a benign renal neo-plasm with peak age of occurrence in the fifthor sixth decade and a 2:1 female preponder-ance [1]. Metanephric adenoma is asymptom-atic in approximately 50% of patients; abdom-inal pain and hematuria are common clinicalsymptoms. Polycythemia, a characteristicfinding seen in approximately 10% of patientswith metanephric adenoma, promptly disap-pears after surgical resection [22].

Metanephric adenoma is histologicallycharacterized by the arrangement of monoto-nous small blue embryonal epithelial cells inan acinar, tubular, or sheetlike configuration[21]. Abundant psammoma bodies are com-monly found.

Metanephric adenoma typically appears asa well-defined, unencapsulated, solitary solidmass [21, 22] (Fig. 3). It commonly appearsas a hyperattenuating mass on unenhanced

CT; large tumors appear as heterogeneous,hypovascular masses with frequent foci ofhemorrhage and necrosis [23, 24]. Calcifica-tion is seen in 20% of cases. Metanephric ad-enoma shows a hypointense signal on T1-weighted MRI and a slightly hyperintensesignal on T2-weighted MRI [25]. Meta-nephric adenoma appears as an expansile hy-poechoic or hyperechoic mass on sonogra-phy. True cystic forms of metanephricadenoma are rare [26].

Mesenchymal NeoplasmsAngiomyolipoma

Angiomyolipoma (AML) is the most com-mon benign mesenchymal neoplasm; it is com-posed of variable proportions of blood vessels,smooth muscle, and adipose tissue [1]. AMLsare now included under the umbrella term“neoplasms of the perivascular epithelioidcells,” which are also referred to as PEComas[27]. Renal AMLs consist of two distinct his-tologic subtypes, classic triphasic and mono-typic epithelioid. Epithelioid AMLs typicallydo not show macroscopic fat and appear assoft-tissue masses and are thus indistinguish-able from other solid renal masses. This raresubtype of AML is potentially malignant andmay exhibit aggressive biology, including re-currence, metastasis, and death. It will not befurther discussed in this article [27, 28].

Classic AML may occur either sporadi-cally or in association with tuberous sclerosiscomplex (TSC). Sporadic renal AMLs show a4:1 female preponderance and are more likelyto be solitary and symptomatic [29]. Patientswith TSC harbor small, multicentric, asymp-tomatic AMLs; 80% of patients with severeTSC have renal AMLs [30]. The morphologyof AMLs depends on the relative proportionsof various components. Profuse elastin-poor,

A B

Fig. 1—72-year-old man with hereditary oncocytosis syndrome. Coronal contrast-enhanced CT scan during nephrographic phase shows bilateral solid renal masses (arrows) that were characterized as oncocytomas on histopathology.

Fig. 2—64-year-old man with histologically proven oncocytoma. K = kidney.A, Axial fat-saturated, T2-weighted gradient-refocused echo image shows expansile, solid right renal mass (arrow) with hyperintense central scar (S).B, Axial fat-saturated, gadolinium-enhanced T1-weighted 3D gradient-refocused echo image shows right kidney mass (arrow) with hypointense central scar (S).

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dysmorphic blood vessels predispose to aneu-rysm formation and hemorrhage [29]. Largetumor size (> 4 cm) and diameter of the in-tralesional aneurysms (> 5 mm) correlate di-rectly with tumor-related hemorrhage inAMLs [31].

On sonography, small AMLs appear uni-formly hyperechoic without a hypoechoic rimor intralesional cysts [32] (Fig. 4). LargeAMLs appear as variegated masses with mac-roscopic fat, hemorrhage, and hypervascularsoft-tissue components. Intralesional aneu-rysms are seen in large tumors as well. Thepresence of macroscopic fat on CT or MRI ischaracteristic of AMLs (Fig. 5). Loss of sig-nal intensity on frequency-selective fat-sup-pressed MRI definitively identifies macro-scopic fat [30] (Fig. 6). However, a multitudeof renal neoplasms, including RCC, oncocy-toma, lipoma, and liposarcoma, may show ei-ther intratumoral fat or engulfed perirenal fat

[33]. Approximately 4.5% of AMLs may notshow identifiable macroscopic fat and are in-distinguishable from RCC on imaging studiesalone (Fig. 7). Recent studies indicate that incontradistinction to RCCs, AMLs with mini-mal fat show uniform, prolonged contrast en-hancement and a higher signal intensity indexon double-echo, chemical shift FLASH MRI[34, 35].

HemangiomaRenal hemangioma is a rare benign mesen-

chymal neoplasm that consists of multipleendothelium-lined, blood-filled vascularspaces [1]. It commonly affects young adultswith no specific sex predilection. Recurrentepisodes of hematuria and renal colic are typ-ical presenting symptoms; however, inciden-tal diagnosis in asymptomatic patients is alsocommon [36]. Hemangiomas of the kidneymay be associated with systemic syndromes

such as Sturge-Weber and Klippel-Trénaunayand with systemic angiomatosis [1]. Cavern-ous hemangiomas are more common than thecapillary variants.

Hemangioma of the kidney occurs as anunencapsulated, unicentric, solitary tumorthat frequently arises from the renal pyra-mids or the pelvis [1, 37]. Hemangiomasshow variable echogenicity on sonographyand hyperintensity on T2-weighted MRI[38] (Fig. 8A). Contrast-enhanced CT andMRI of renal hemangiomas may showearly, intense enhancement (Fig. 8B). Per-sistent contrast enhancement on delayedimages is fairly characteristic of renal he-mangiomas [37].

LymphangiomaLymphangioma of the kidney is a rare be-

nign cystic tumor that most often arises fromthe peripelvic region or renal sinus [1]. It

Fig. 3—Contrast-enhanced axial CT scan in 60-year-old woman with hematuria shows hypoattenuating, expansile solid mass (arrows) in left kidney. Radical nephrectomy showed mass to be metanephric adenoma. K = kidney.

Fig. 4—43-year-old woman with hematuria. Transverse sonogram shows uniformly echogenic mass (arrows) in upper pole of left kidney (K) that was proven to be angiomyolipoma.

Fig. 5—58-year-old woman with angiomyolipoma of kidney. Sagittal contrast-enhanced CT scan shows exophytic renal mass (arrows) with foci of macroscopic fat (arrowhead).

A B

Fig. 6—38-year-old woman with documented tuberous sclerosis complex and renal angiomyolipomas.A, Axial in-phase T1-weighted 2D gradient-refocused echo MR image shows bilateral multicentric renal masses that have increased signal intensity (arrows).B, Axial fat-saturated T2-weighted 2D gradient-refocused echo MR image shows marked drop in signal intensity of masses (arrows).

Fig. 7—55-year-old woman who underwent partial nephrectomy for serendipitously detected renal mass. Axial contrast-enhanced CT scan shows exophytic soft-tissue mass (arrow). Histopathology showed lipid-poor angiomyolipoma.



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may also uncommonly arise from the lym-phatics of the capsule or the cortex [39]. His-tologically, lymphangiomas consist of com-municating endothelium-lined spaces thatcontain clear fluid [1]. The septa may showlymphoid cells.

Renal lymphangioma may occur either asan isolated finding or in association with peri-nephric or systemic lymphangiomatosis [39].It may appear as a localized process or a dif-fusely cystic lesion. Lymphangioma typicallyappears as a well-demarcated, uni- or mul-tilocular cystic neoplasm that most com-monly arises from the renal sinus region or inthe perinephric space [40, 41] (Fig. 9).

LeiomyomaRenal leiomyomas are rare benign smooth-

muscle neoplasms that mostly occur in adultsas incidental findings [1]. Renal capsule is the

most common target site of leiomyomas;rarely, leiomyomas originate from the renalpelvis or cortex. Intersecting fascicles of spin-dle cells that show immunoreactivity to actinor desmin (smooth-muscle markers) are char-acteristic histologic features [1].

Leiomyomas of the kidney commonly ap-pear as well-circumscribed, homogeneous, ex-ophytic solid masses that show uniform en-hancement on contrast-enhanced CT [42](Fig. 10). Larger tumors are heterogeneous be-cause of hemorrhage and cystic or myxoid de-generation [43, 44]. Calcification is uncom-mon. However, the CT findings of leiomyomasof the kidney may be variable and may includecystic, complex cystic–solid, or purely solidmorphology [44]. Renal leiomyomas mayshow hypervascularity on catheter angiogra-phy because they are predominantly suppliedby capsular vessels [42, 45].

Juxtaglomerular Cell Neoplasm (Reninoma)Juxtaglomerular cell (JGC) neoplasm is an

extremely rare, benign renal neoplasm ofmyoendocrine cell origin [46]. The peak ageof incidence is in the second and third decadesand a 2:1 female preponderance is seen. JGCneoplasm is clinically characterized by a triadof findings: poorly controlled hypertension,hypokalemia, and high plasma renin activity[47]. Histologically, JGC neoplasm consistsof sheets of polygonal or spindle cells and acharacteristic, complex, hemangiopericyticangioarchitecture [1]. The presence of rhom-boid renin protogranules is diagnostic of JGCneoplasm [46].

JGC neoplasm typically appears as a uni-lateral, well-circumscribed, cortical tumorthat usually measures less than 3 cm [13](Fig. 11). Despite profuse vascularity, JGCneoplasms appear hypovascular on contrast-

A B

Fig. 8—60-year-old man with hematuria and histologically proven hemangioma.A, Axial fat-saturated T2-weighted 2D gradient-refocused echo MR image shows hyperintense left kidney mass in renal sinus (arrow).B, Axial fat-saturated gadolinium-enhanced T1-weighted 3D gradient-refocused echo MR image shows contrast enhancement of left renal sinus mass (arrows).

Fig. 9—47-year-old man with bilateral multiple renal sinuses and perinephric lymphangiomatosis. Unenhanced axial CT scan shows multicentric cystic masses in renal sinus and perinephric spaces (arrows).

Fig. 10—43-year-old woman with renal leiomyoma of capsular origin. Axial contrast-enhanced CT scan shows large, fairly homogeneous exophytic mass (arrows) arising from left kidney (K).

Fig. 11—23-year-old woman with hypertension refractory to standard treatment. Axial unenhanced CT scan shows large, expansile right renal mass (arrow) that was histologically proven to be juxtaglomerular cell neoplasm (reninoma). K = kidney, M = mass.

Fig. 12—57-year-old woman with incidental medullary fibroma (arrowhead). Patient underwent radical nephrectomy for renal cell carcinoma (Ca, arrow) of right kidney.

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enhanced CT and MRI, possibly because ofrenin-induced vasoconstriction [48, 49]. JGCneoplasms may show delayed contrast en-hancement. Imaging findings of JGC neo-plasms are nonspecific and indistinguishablefrom other solid renal neoplasms.

Renomedullary Interstitial Cell TumorAlso referred to as medullary fibromas,

renomedullary interstitial cell tumors are be-nign neoplasms that arise from renomedul-lary interstitial cells, small stellate cells thatare thought to play a role in blood pressurehomeostasis [50]. Renomedullary interstitialcell tumors are common incidental findingsthat are present in 50% of adults in autopsyseries [1].

Most renomedullary interstitial cell tumorsare small and typically measure less than 5mm. The renal pyramid is the characteristiclocation of renomedullary interstitial cell tu-mors [1]. Rarely, large renomedullary inter-stitial cell tumors extend into the renal pelvis.They appear as nonenhancing, hypoattenuat-ing renal medullary solid lesions without cal-cification (Fig. 12).

Mixed Epithelial and Mesenchymal Neoplasms

Mixed epithelial and mesenchymal neo-plasms comprise two histologically distinctentities: mixed epithelial and stromal tu-mors and cystic nephromas. However, re-cent studies have found remarkable demo-graphic, clinical, and pathologic similaritiesamong these entities and a new name, renalepithelial and stromal tumor, has been pro-posed [51, 52]. This nomenclature is stillnew and has yet to be universally accepted;we will discuss these two entities separately

in this article according to WHO taxonomicschemata.

Mixed Epithelial and Stromal TumorThe entity mixed epithelial and stromal tu-

mor was previously called by several descrip-tive names reflecting variegated tumor histol-ogy. It is now thought that mixed epithelialand stromal tumor was previously referred toas leiomyomatous renal hamartoma, mul-tilocular cyst with ovarian stroma, cystichamartoma of the renal pelvis, and adult me-soblastic nephroma [53–55]. The unifyingterm, mixed epithelial and stromal tumor, wasfirst coined by Michal and Syrucek in 1998[56]; two recent large series have largely con-tributed to our understanding of mixed epithe-lial and stromal tumors [57, 58].

Mixed epithelial and stromal tumors occuralmost exclusively in perimenopausal women(6:1 female preponderance); most patients arereceiving estrogen therapy [57, 58]. Twenty-five percent of the tumors present as inciden-tal findings; most patients manifest nonspe-cific symptoms of flank pain and hematuria.Pathologically, mixed epithelial and stromaltumor is a benign, bimorphic solid–cysticneoplasm that consists of epithelium-linedcysts or microcysts and variably cellular spin-dle-cell, ovarianlike (estrogen- or progester-one-receptor positive) stroma [57, 58].

On imaging, mixed epithelial and stromaltumors typically appear as expansile, com-plex, cystic–solid masses with heterogeneousand delayed enhancement [59] (Fig. 13). Theproportion of cystic and solid constituentsvaries in any given case. The stromal compo-nent of the tumor is thought to be responsiblefor the hypointense signal on T2-weightedMRI with delayed contrast enhancement [59].

Large mixed epithelial and stromal tumorsmay herniate into the renal pelvis. The tumorstypically show benign biologic behaviorwithout recurrence or metastasis; however,aggressive mixed epithelial and stromal tu-mors with sarcomatous transformation of thestromal component have been described [60].

Cystic NephromaCystic nephroma is a benign cystic neo-

plasm that affects predominantly middle-aged,perimenopausal women [1]. Adult-onset cysticnephroma is histogenetically and morphologi-cally different from pediatric cystic nephroma[39, 61]. Morphologically, cystic nephromasare composed of encapsulated, noncommuni-cating cysts with thin septations. By definition,cystic nephromas are characterized by the ab-sence of a solid component or necrosis [1]. Onhistology, the cysts are lined by a monolayer ofhobnail epithelium; the fibrous septa may bepaucicellular or cellular [1].

Cystic nephroma appears as a well-demar-cated, solitary, multilocular cystic lesion withthin septations (Fig. 14A). The cystic massmay protrude into the renal pelvis and causehemorrhage or urinary obstruction [62](Fig. 14B).

ConclusionBenign renal tumors that occur in adults

cover a wide spectrum and show character-istic histology, histogenesis, and anatomicdistribution. Some benign tumors of the kid-ney (such as angiomyolipomas, mixed epi-thelial and mesenchymal tumors, leiomyo-mas, and hemangiomas) show characteristicimaging findings and regional distributionthat permit their diagnosis (Appendix 2). Al-though leiomyomas originate from the renal

A B

Fig. 13—40-year-old woman with histologically proven mixed epithelial and stromal tumor of kidney. Axial contrast-enhanced CT scan shows large complex cystic left kidney (K) mass (arrows) with septations and solid components.

Fig. 14—50-year-old woman with cystic nephroma.A, Coronal contrast-enhanced CT scan shows lobulated, expansile, cystic mass (M) in left kidney (arrow) that compresses calyces (C).B, Coronal T2-weighted MR image shows multilocular, septated cystic mass in left kidney (arrow) that herniates into renal pelvis. C = calyces.



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capsule, hemangiomas typically arise fromthe renal sinus. Renomedullary interstitialcell tumors (also known as medullary fibro-mas) are commonly confined to the renalmedulla. Approximately one third of largeoncocytomas typically show a central stel-late scar. Cystic nephromas show septatedcysts, macroscopic fat predominates in mostangiomyolipomas, and metanephric ade-nomas are commonly solid. Mixed epithelialand stromal tumors consist of solid areas andcysts that may herniate into the renal pelvis.However, most benign renal tumors appearas solid enhancing masses and are thus indis-tinguishable from the more common malig-nant renal neoplasms, notably RCCs. Biopsyof the renal mass may help establish the de-finitive diagnosis and may obviate aggres-sive treatment.

References1. Eble JN, Sauter G, Epstein JI, Sesterhenn IA, eds.

World Health Organization classification of tu-

mors: pathology and genetics of tumors of the uri-

nary system and male genital organs. Lyon, France:

IARC Press, 2004

2. Kutikov A, Fossett LK, Ramchandani P, et al. Inci-

dence of benign pathologic findings at partial ne-

phrectomy for solitary renal mass presumed to be

renal cell carcinoma on preoperative imaging. Urol-

ogy 2006; 68:737–740

3. Beland MD, Mayo-Smith WW, Dupuy DE, Cronan

JJ, DeLellis RA. Diagnostic yield of 58 consecutive

imaging-guided biopsies of solid renal masses:

should we biopsy all that are indeterminate? AJR

2007; 188:792–797

4. Maturen KE, Nghiem HV, Caoili EM, Higgins EG,

Wolf JS Jr, Wood DP Jr. Renal mass core biopsy: ac-

curacy and impact on clinical management. AJR

2007; 188:563–570

5. Vasudevan A, Davies RJ, Shannon BA, Cohen RJ.

Incidental renal tumours: the frequency of benign

lesions and the role of preoperative core biopsy.

BJU Int 2006; 97:946–949

6. Silverman SG, Gan YU, Mortele KJ, Tuncali K, Ci-

bas ES. Renal masses in the adult patient: the role

of percutaneous biopsy. Radiology 2006; 240:6–22

7. Shah RB, Bakshi N, Hafez KS, Wood DP Jr, Kunju

LP. Image-guided biopsy in the evaluation of renal

mass lesions in contemporary urological practice:

indications, adequacy, clinical impact, and limita-

tions of the pathological diagnosis. Hum Pathol

2005; 36:1309–1315

8. Jones TD, Eble JN, Cheng L. Application of mo-

lecular diagnostic techniques to renal epithelial neo-

plasms. Clin Lab Med 2005; 25:279–303

9. Rowsell C, Fleshner N, Marrano P, Squire J,

Evans A. Papillary renal cell carcinoma within a

renal oncocytoma: case report of an incidental

finding of a tumour within a tumour. J Clin Pathol

2007; 60:426–428

10. Venkatesh R, Weld K, Ames CD, et al. Laparo-

scopic partial nephrectomy for renal masses: effect

of tumor location. Urology 2006; 67:1169–1174;

discussion 1174

11. Lotan Y, Duchene DA, Cadeddu JA, Sagalowsky

AI, Koeneman KS. Changing management of or-

gan-confined renal masses. J Endourol 2004;

18:263–268

12. Storkel S, Pannen B, Thoenes W, Steart PV, Wagner

S, Drenckhahn D. Intercalated cells as a probable

source for the development of renal oncocytoma.

Virchows Arch B Cell Pathol Incl Mol Pathol 1988;

56:185–189

13. Prasad SR, Narra VR, Shah R, et al. Segmental dis-

orders of the nephron: histopathological and imag-

ing perspective. Br J Radiol 2007; 80:593–602

14. Choyke PL. Imaging of hereditary renal cancer. Ra-

diol Clin North Am 2003; 41:1037–1051

15. Quinn MJ, Hartman DS, Friedman AC, et al. Renal

oncocytoma: new observations. Radiology 1984;

153:49–53

16. Ishikawa I, Kovacs G. High incidence of papillary

renal cell tumours in patients on chronic haemodi-

alysis. Histopathology 1993; 22:135–139

17. Kiyoshima K, Oda Y, Nakamura T, et al. Multicen-

tric papillary renal cell carcinoma associated with

renal adenomatosis. Pathol Int 2004; 54:266–272

18. Kovacs G. High frequency of papillary renal-cell tu-

mours in end-stage kidneys: is there a molecular ge-

netic explanation? Nephrol Dial Transplant 1995;

10:593–596

19. Kovacs G, Fuzesi L, Emanual A, Kung HF. Cyto-

genetics of papillary renal cell tumors. Genes Chro-

mosomes Cancer 1991; 3:249–255

20. Brunelli M, Eble JN, Zhang S, Martignoni G, Cheng

L. Gains of chromosomes 7, 17, 12, 16, and 20 and

loss of Y occur early in the evolution of papillary re-

nal cell neoplasia: a fluorescent in situ hybridization

study. Mod Pathol 2003; 16:1053–1059

21. Argani P. Metanephric neoplasms: the hyperdiffer-

entiated, benign end of the Wilms tumor spectrum?

Clin Lab Med 2005; 25:379–392

22. Davis CJ Jr, Barton JH, Sesterhenn IA, Mostofi

FK. Metanephric adenoma: clinicopathological

study of fifty patients. Am J Surg Pathol 1995;

19:1101–1114

23. Fielding JR, Visweswaran A, Silverman SG, Granter

SR, Renshaw AA. CT and ultrasound features of me-

tanephric adenoma in adults with pathologic correla-

tion. J Comput Assist Tomogr 1999; 23:441–444

24. Lerut E, Roskams T, Joniau S, et al. Metanephric

adenoma during pregnancy: clinical presenta-

tion, histology, and cytogenetics. Hum Pathol

2006; 37:1227–1232

25. Araki T, Hata H, Asakawa E, Araki T. MRI of me-

tanephric adenoma. J Comput Assist Tomogr 1998;

22:87–90

26. Patankar T, Punekar S, Madiwale C, Prasad S, Han-

chate V. Metanephric adenoma in a solitary kidney.

Br J Radiol 1999; 72:80–81

27. Prasad SR, Sahani DV, Mino-Kenudson M, et al.

Neoplasms of the perivascular epithelioid cell in-

volving the abdomen and the pelvis: cross-sectional

imaging findings. J Comput Assist Tomogr 2007;

31:688–696

28. Martignoni G, Pea M, Rigaud G, et al. Renal angi-

omyolipoma with epithelioid sarcomatous transfor-

mation and metastases: demonstration of the same

genetic defects in the primary and metastatic le-

sions. Am J Surg Pathol 2000; 24:889–894

29. Eble JN. Angiomyolipoma of kidney. Semin Diagn

Pathol 1998; 15:21–40

30. Casper KA, Donnelly LF, Chen B, Bissler JJ. Tu-

berous sclerosis complex: renal imaging findings.

Radiology 2002; 225:451–456

31. Yamakado K, Tanaka N, Nakagawa T, Kobayashi S,

Yanagawa M, Takeda K. Renal angiomyolipoma:

relationships between tumor size, aneurysm forma-

tion, and rupture. Radiology 2002; 225:78–82

32. Siegel CL, Middleton WD, Teefey SA, McClennan

BL. Angiomyolipoma and renal cell carcinoma: US

differentiation. Radiology 1996; 198:789–793

33. Helenon O, Merran S, Paraf F, et al. Unusual fat-

containing tumors of the kidney: a diagnostic di-

lemma. RadioGraphics 1997; 17:129–144

34. Kim JK, Park SY, Shon JH, Cho KS. Angiomyoli-

poma with minimal fat: differentiation from renal

cell carcinoma at biphasic helical CT. Radiology

2004; 230:677–684

35. Kim JK, Kim SH, Jang YJ, et al. Renal angiomyo-

lipoma with minimal fat: differentiation from other

neoplasms at double-echo chemical shift FLASH

MR imaging. Radiology 2006; 239:174–180

36. Daneshmand S, Huffman JL. Endoscopic man-

agement of renal hemangioma. J Urol 2002;

167:488–489

37. Prasad SR, Humphrey PA, Menias CO, et al. Neo-

plasms of the renal medulla: radiologic–pathologic

correlation. RadioGraphics 2005; 25:369–380

38. Lee HS, Koh BH, Kim JW, et al. Radiologic find-

ings of renal hemangioma: report of three cases. Ko-

rean J Radiol 2000; 1:60–63

39. Bisceglia M, Galliani CA, Senger C, Stallone C,

Sessa A. Renal cystic diseases: a review. Adv Anat

Pathol 2006; 13:26–56

40. Gupta R, Sharma R, Gamanagatti S, Dogra PN, Ku-

mar A. Unilateral renal lymphangiectasia: imaging

appearance on sonography, CT and MRI. Int Urol

Nephrol 2007; 39:361–364; epub 2006 Dec 14

41. Levine E. Lymphangioma presenting as a small

renal mass during childhood. Urol Radiol 1992;

14:155–158

Prasad et al.


158.fm — 12/7/07

42. Lee SY, Hsu HH, Chang CT, Yang CW, Wong YC,

Wang LJ. Renal capsular leiomyoma: imaging fea-

tures on computed tomography and angiography.

Nephrol Dial Transplant 2006; 21:228–229

43. Nagar AM, Raut AA, Narlawar RS, Bhatgadde VL,

Rege S, Thapar V. Giant renal capsular leiomyoma:

study of two cases. Br J Radiol 2004; 77:957–958

44. Steiner M, Quinlan D, Goldman SM, et al. Leiomy-

oma of the kidney: presentation of 4 new cases and

the role of computerized tomography. J Urol 1990;

143:994–998

45. Inoue K, Tsukuda S, Kayano H, Tanaka J, Heshiki

A. A case of hypervascular renal capsule leiomy-

oma. Radiat Med 2000; 18:323–326

46. Martin SA, Mynderse LA, Lager DJ, Cheville JC.

Juxtaglomerular cell tumor: a clinicopathologic

study of four cases and review of the literature. Am

J Clin Pathol 2001; 116:854–863

47. Conn JW, Cohen EL, Lucas CP, et al. Primary re-

ninism: hypertension, hyperreninemia, and secondary

aldosteronism due to renin-producing juxtaglomeru-

lar cell tumors. Arch Intern Med 1972; 130:682–696

48. Dunnick NR, Hartman DS, Ford KK, Davis CJ Jr,

Amis ES Jr. The radiology of juxtaglomerular tu-

mors. Radiology 1983; 147:321–326

49. Tanabe A, Naruse M, Ogawa T, et al. Dynamic com-

puter tomography is useful in the differential diag-

nosis of juxtaglomerular cell tumor and renal cell

carcinoma. Hypertens Res 2001; 24:331–336

50. Lerman RJ, Pitcock JA, Stephenson P, Muirhead

EE. Renomedullary interstitial cell tumor (for-

merly fibroma of renal medulla). Hum Pathol

1972; 3:559–568

51. Antic T, Perry KT, Harrison K, et al. Mixed epithe-

lial and stromal tumor of the kidney and cystic ne-

phroma share overlapping features: reappraisal of

15 lesions. Arch Pathol Lab Med 2006; 130:80–85

52. Turbiner J, Amin MB, Humphrey PA, et al. Cystic

nephroma and mixed epithelial and stromal tumor

of kidney: a detailed clinicopathologic analysis of

34 cases and proposal for renal epithelial and stro-

mal tumor (REST) as a unifying term. Am J Surg

Pathol 2007; 31:489–500

53. Pawade J, Soosay GN, Delprado W, Parkinson MC,

Rode J. Cystic hamartoma of the renal pelvis. Am J

Surg Pathol 1993; 17:1169–1175

54. Durham JR, Bostwick DG, Farrow GM, Ohorodnik

JM. Mesoblastic nephroma of adulthood: report of

three cases. Am J Surg Pathol 1993; 17:1029–1038

55. Yoshida S, Nakagomi K, Goto S, Ozawa T. Cystic

hamartoma of the renal pelvis. Int J Urol 2004;

11:653–655

56. Michal M, Syrucek M. Benign mixed epithelial and

stromal tumor of the kidney. Pathol Res Pract 1998;

194:445–448

57. Michal M, Hes O, Bisceglia M, et al. Mixed epithe-

lial and stromal tumors of the kidney: a report of 22

cases. Virchows Arch 2004; 445:359–367

58. Adsay NV, Eble JN, Srigley JR, Jones EC, Grignon

DJ. Mixed epithelial and stromal tumor of the kid-

ney. Am J Surg Pathol 2000; 24:958–970

59. Park HS, Kim SH, Kim SH, et al. Benign mixed ep-

ithelial and stromal tumor of the kidney: imaging

findings. J Comput Assist Tomogr 2005; 29:786–789

60. Svec A, Hes O, Michal M, Zachoval R. Malignant

mixed epithelial and stromal tumor of the kidney.

Virchows Arch 2001; 439:700–702

61. Eble JN, Bonsib SM. Extensively cystic renal neo-

plasms: cystic nephroma, cystic partially differen-

tiated nephroblastoma, multilocular cystic renal cell

carcinoma, and cystic hamartoma of renal pelvis.

Semin Diagn Pathol 1998; 15:2–20

62. Kural AR, Obek C, Ozbay G, Onder AU. Multiloc-

ular cystic nephroma: an unusual localization. Urol-

ogy 1998; 52:897–899

APPENDIX 1: World Health Organization (WHO) Histological Classification of Benign Renal Neoplasms

Renal Cell Tumors Metanephric Tumors Mesenchymal Tumors Mixed Epithelial and Mesenchymal Tumors

Oncocytoma Metanephric adenoma Angiomyolipoma Cystic nephroma

Papillary adenoma Metanephric adenofibroma Leiomyoma Mixed epithelial and stromal tumor

Metanephric stromal tumor Hemangioma

Lymphangioma

Reninoma

Fibroma

Schwannoma

APPENDIX 2: Making Sense of Adult, Benign Renal Neoplasms: A Pattern-Based Imaging Approach

Soft-Tissue Mass Fatty Mass Cystic Mass Cortical Mass Medullary Mass

Oncocytoma Angiomyolipoma (AML) Cystic nephroma Leiomyoma Hemangioma

Lipid-poor AML Mixed epithelial and stromal tumor Oncocytoma Fibroma

Leiomyoma Metanephric adenoma (rare) AML Mixed epithelial and stromal tumor

Hemangioma Lymphangioma AML

Reninoma Leiomyoma

Fibroma

Schwannoma

F O R Y O U R I N F O R M A T I O N

This article is available for CME credit. See www.arrs.org for more information.

benign renal neoplasms

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