Renal Tubulocystic Carcinoma Is Closely Related to Papillary Renal Cell Carcinoma: Implications for...

Renal Tubulocystic Carcinoma Is CloselyRelated to Papillary Renal Cell Carcinoma:Implications for Pathologic Classification

Ming Zhou, MD, PhD,* Ximing J. Yang, MD, PhD,w Jose I. Lopez, MD,z Rajal B. Shah, MD,yOndrej Hes, MD,J Steven S. Shen, MD, PhD,z Rongshan Li, MD, PhD,# Yu Yang, MD, **

Fan Lin, MD, PhD, w w Paul Elson, PhD,* Linda Sercia, BS,* Cristina Magi-Galluzzi, MD, PhD,*and Ray Tubbs, DO*

Abstract: Tubulocystic carcinoma of the kidney (TC-RCC) is a

rare renal tumor with unique gross and microscopic features

unlike other types of renal cell carcinoma (RCC). Several recent

studies recommend that it should be classified as a distinct RCC

subtype. In this study, we provide pathologic and cytogenetic

evidence supporting that TC-RCC is closely related to papillary

RCC (PRCC). This study included 20 cases of renal tumors that

partially or exclusively comprised a TC-RCC component.

Pathologic examination documented the gross and microscopic

features of TC-RCC, including multicentricity and the presence

of concomitant PRCC and papillary adenoma. Formalin-fixed,

paraffin-embedded sections from 12 TC-RCC and 20 PRCC

were subjected to a multicolor fluorescence in situ hybridization

assay containing probes for chromosomes 7, 17, and Y. One

hundred nuclei were examined to enumerate the copy numbers of

chromosomes in each tumor and its corresponding normal kidney

tissue. A tumor with a percentage of cells harboring a chromosomal

change Zmean+3 SD of normal tissue was considered to harbor

that chromosomal change, and a tumor with a percentage of

cells with null Y chromosome count (loss of Y chromosome)

Zmean+3SD of normal tissue was considered to harbor Y

chromosome loss. Four of the 20 TC-RCCs were multicentric.

Ten had associated PRCC or papillary adenoma within the

same kidney as the TC-RCC. In 4 cases, the tubulocystic and

papillary components were admixed together within the same

lesion. The tumor cells lining both the tubulocystic and papillary

components had similar cytologic features. Ten of 12 TC-RCCs

had a chromosome 7 gain, 8 of 12 cases had a chromosome 17

gain, and 8 of 9 cases had a loss of Y chromosome. Six of 9 cases

with all 3 chromosomes studied had a gain of chromosomes

7 and 17 and a loss of Y chromosome. Our study shows that

TC-RCCs and PRCCs are closely related entities. With its

distinctive gross and microscopic features, TC-RCC may be

considered a unique ‘‘morphologic entity.’’ However, before it is

accepted as a distinct renal cell carcinoma subtype, further

studies are needed to document a characteristic molecular

signature associated with this tumor.

Key Words: kidney, tubulocystic carcinoma, papillary carcinoma,

cytogenetics

(Am J Surg Pathol 2009;33:1840–1849)

Tubulocystic carcinoma of the kidney (TC-RCC) is apeculiar renal tumor composed of well-differentiated

tubules and cysts lined by tumor cells with eosinophiliccytoplasm and prominent nucleoli.10 Its distinctivemorphology was first recognized by Dr George Farrow,who collected a number of these cases over a period ofmany years and reported them in an abstract presentedat an annual meeting of the United States and CanadaAcademy of Pathology. MacLennan et al11 later reported8 cases of renal tumors that displayed the morphologicfeatures of TC-RCC. Although initially believed to bederived from the collecting ducts of Bellini,11 thesereported tumors were of low-grade malignancy whosebehavior differed significantly from the classical highlyaggressive collecting duct carcinomas of the kidney.Therefore, the authors coined the term ‘‘low-gradecollecting duct carcinoma’’ for this peculiar renal tumor.

Recently, we and other investigators published 3studies on the clinicopathologic, molecular, and immuno-histochemical features of TC-RCC.1,2,20 Of 54 casesreported in these studies, all had characteristic micro-scopic features with tightly packed tubules and small cystsseparated by delicate fibrous septa. The indolent nature ofthese tumors was suggested in these 3 studies, with 44cases presenting at pT1, 6 cases at pT2, and 3 cases at T3.Aggressive clinical behavior was rarely encountered. Onecase in our study developed pelvic lymph node metastasis,whereas 1 patient in Amin et al’s series1 developed localrecurrence and 2 patients developed distant metastasesinvolving bone and liver. These studies argued for TC-RCCCopyright r 2009 by Lippincott Williams & Wilkins

From the *Cleveland Clinic, Cleveland, OH; wNorthwestern UniversityMedical School, Chicago, IL; zHospital de Cruces, Basque CountryUniversity, Barakaldo, Bizkaia, Spain; yUniversity of Michigan, AnnArbor, MI; JCharles’ University Hospital, Plzen, Czech Republic;zThe Methodist Hospital, Houston, TX; #Wisconsin MedicalCollege, Milwaukee, WS; **Peking University, Beijing, China; andwwGeisinger Medical Center, Danville, PA.

Correspondence: Ming Zhou, MD, PhD, Department of Pathology,Cleveland Clinic Foundation, L25, 9500 Euclid Ave, Cleveland, OH(e-mail: [email protected]).

ORIGINAL ARTICLE

1840 | www.ajsp.com Am J Surg Pathol � Volume 33, Number 12, December 2009

to be classified as a distinct renal cell carcinoma (RCC)subtype.

However, these studies also showed considerablesimilarity between TC-RCC and another RCC subtype,papillary RCC (PRCC). Our study documented concur-rent TC-RCC and PRCC in 40% (5/15) cases.20 Eighty-seven percent of the cases in the 3 published studies werepositive for AMACR, a marker for the proximal renaltubules,18,22 and a majority of cases were also variablypositive for cytokeratin 7. This immunophenotype is verysimilar to that of PRCC.15,18 Molecular evaluation wascarried out on 1 case in our study.20 On the basis of thegene expression profile, TC-RCC clustered with PRCCand indicated genetic similarity between the 2 subtypes.By comparative genomic microarray analysis, this casealso had a gain of chromosome 17, a cytogenetic changecharacteristic of PRCC.

To further investigate the relationship betweenTC-RCC and PRCC, we performed a detailed pathologicanalysis of 20 cases of TC-RCC with emphasis on theassociation of TC-RCC with PRCC. In addition, weanalyzed cytogenetic features, namely, gains of chromo-somes 7 and 17 and loss of Y chromosome, in a subset ofTC-RCC.

MATERIALS AND METHODS

Pathologic ReviewThis study included 20 cases of renal tumors that

comprised exclusively or partially of TC-RCC. Thirteencases were reported in our earlier study.20 Cases weresubmitted from hospitals in the United States (n=16),Spain (n=2), China (n=1), and the Czech Republic(n=1). Demographic and clinical information wascollected according to protocols approved by the authors’institutional review boards. Pathologic examination ofhematoxylin and eosin-stained sections was performedto document microscopic features of TC-RCC. Specialattention was paid to concomitant papillary lesions,including PRCC and papillary adenomas, and whetherTC-RCC and papillary lesions were separate from eachother or admixed when present within the same ne-phrectomy specimen. If the TC-RCC and PRCC compo-nents were admixed within the same lesion, the percentageof each component was estimated.

ImmunohistochemistryThree cases with both tubulocystic and papillary

components were stained for cytokeratin 7 (1:40 dilution,Dako, Carpinteria, CA), cytokeratin 19 (1:10 dilution,Invitrogen, Carlsbad, CA), 34bE12 (prediluted, Enzo,Farmingdale, NY), AMACR (1:100 dilution, Zeta, SierraMadre, CA), CD10 (1:5 dilution, Novacastra, Newcastleupon Tyne, UK), and PAX-2 (1:50 dilution, Invitrogen).In brief, the 5-mm tissue sections were antigen-retrievedaccording to the specifications of the primary antibodymanufacturers. The slides were then incubated sequen-tially with primary antibody, biotinylated secondaryantibody, avidin-peroxidase complex (Ventana, Tucson,

AZ), and a chromogenic substrate, diaminobenzidine.The immunostaining was performed on a Ventana Bench-mark automatic stainer (Ventana). The immunostainswere evaluated in a semiquantitative manner, rangingfrom negative, focally positive, and positive.

Fluorescence In Situ HybridizationFor each case, a 4-mm section from a representative,

formalin-fixed, paraffin-embedded block was cut and bakedat 65±51C overnight or for a minimum of 5 hours.The slides were then sequentially deparaffinized in xylene,washed in absolute alcohol, and air-dried. Pepsin wasused to digest the tissue at 371C for 40 minutes.Fluorescence in situ hybridization (FISH) was performedwith a UroVysion bladder cancer recurrence kit thatcontained the centromeric probes for chromosome7 (CEP7, spectrum green) and chromosome 17 (CEP17, spectrum aqua) (Abbott Molecular/Vysis Cat. no.36-161070). Probes for chromosome 3 (CEP3, spectrumred) chromosome 9 (9p21, Spectrum gold) were alsopresent in the probe mixture but were not evaluated inthis study. A centromeric a-satellite DNA probe was usedfor the Y chromosome (Vysis, Downers Grove, IL). Theslide was cover-slipped and sealed with rubber cement.Co-denaturation was carried out at the melting tempera-ture of 731C for 5 minutes by placing the slide in Hybrite.Hybridization was carried out in a 371C humidified Cincubator overnight (12 to 18 h). The coverslip was thenremoved and the slides were washed in 1� SSC/0.3%NP-40 followed by wash in 2� SSC/0.1% NP-40 at roomtemperature. Slides were then air-dried completely indarkness. About 15 to 20 mL Vectashield with a DAPIcounterstain was applied to the target area of the slide.We also performed FISH assay with the same probes(CEP7 and 17) in PRCC as a positive control.

FISH AnalysisThe FISH data were analyzed using methods

described earlier.8 The corresponding hematoxylin andeosin slides were reviewed before the FISH study andareas of tumor and normal renal tubules were marked.For each case, 100 nuclei from normal and tumor areaswere examined for signals from probes under the fluores-cence microscope with 1000�magnification. Normalrenal tubules were used as a control. Definitions ofchromosomal gain and loss of chromosomes 7, 17, and Ywere based on the Gaussian model and related to the non-neoplastic controls. Any tumor with a signal scorebeyond the cut-off value was considered to have a gainor loss of the specific chromosome. The cut-off values foreach probe were set at mean+3 SD of the control values.

RESULTS

Association of TC-RCC With PapillaryRenal Tumors

The pathologic features of 20 TC-RCC cases aresummarized in Table 1. Of these 20 cases, the age of the

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patients ranged from 36 to 94 years (mean age=58.4 y)with 16 male and 4 female patients (male to femaleratio 4:1). Eight patients were treated with radicalnephrectomy, and the remaining 12 patients underwentpartial nephrectomy. Sixteen of 20 cases (80%) presentedas a solitary mass; 4 cases presented as multifocal lesions.Half of the cases10 were pure TC-RCCs that formed well-circumscribed and multicystic masses. Microscopically,the tumors were non-encapsulated but sharply demar-cated from the non-neoplastic renal parenchyma. Thetumors consisted of numerous tubules and cysts linedwith cuboidal or hobnail cells with prominent nucleoli.

Ten cases had associated papillary renal neoplasmswithin the same kidney as TC-RCCs. The papillary compo-nent was found separate from, but in close proximity to,TC-RCC in 6 cases, and admixed with TC-RCC in 3 cases.One case had both an admixed and a separate papillarycomponent.

In 7 cases with a separate papillary renal cellneoplasm component, solitary papillary RCC was foundin 4 cases, multifocal papillary RCC in 1 case, papillaryRCC and multifocal papillary adenomas in 1 case, andsolitary papillary adenoma in 1 case.

In 4 cases tubulocystic and papillary componentswere admixed together within the same lesion (Table 1).Patient 20 had a 6.1-cm cystic mass (Fig. 1A) and severalsatellite nodules. The main tumor was a TC-RCCadmixed with a minor component of PRCC (2%)(Fig. 1B). Foamy histiocytes and psammomatous calcifi-

cation were present in the fibrovascular cores of thepapillae (Fig. 1C). TC-RCC was adjacent to 5 otherPRCCs or papillary adenomas in the same nephrectomyspecimen (Fig. 1D). Patient 15 had an 8-cm tumor consist-ing of 80% of type 2 PRCC and 20% of TC-RCC. These2 components were intimately admixed (Fig. 2A) andthe cells lining both the tubulocystic and papillary compo-nents had similar cytologic features with prominentnucleoli (Fig. 2B). Patient 17 had a 1.6-cm TC-RCCadmixed with PRCC (Fig. 3A). Histiocytes were prominentin the papillary component (Fig. 3B). Both componentscomprised identical oncocytic tumor cells (Figs. 3B, C).Patient 18 had a 2.8-cm TC-RCC admixed with PRCC(Fig. 4A). The papillary component (Fig. 4B) and tubulo-cystic component (Fig. 4C) made up 30% and 70% of thetumor, respectively. Cells in both components had identicalnuclear features (Fig. 4D).

Cytogenetics of Renal Tubulocystic CarcinomaNon-neoplastic renal tubules were assayed for the

copy numbers of chromosomes 7, 17, and Y. The meanand SD was calculated for each chromosome andmean+3 SD was used as the cut-off value for classifyinga tumor as positive for a particular chromosomal change(Table 2). The FISH results for 12 TC-RCC and 20PRCC cases are shown in Table 3 and Figure 5. All 20PRCC cases had gains of chromosomes 7 and 17. Ten of12 TC-RCC cases had a gain of chromosme 7, 8 of 12

TABLE 1. Pathologic Features of Renal Tubulocystic Carcinoma

Case No. Age Sex

Multicentricity

of TC-RCC

TC-RCC

Size (cm)

Pathologic

Stage

Concomitant Papillary Lesions

Within the Same Kidney, but

Separate From TC-RCC Admixed With TC-RCC

1 67 Male Solitary 2.1 T1aN2 PRCC, type 2.11 cm —2 55 Male Solitary 2.5 T1a — —3 71 Male Solitary 2.3 T1a PRCC, type 2.7 cm —4 36 Female Solitary 1.8 T1a — —5 70 Male Multifocal 0.3-2.2 T1a — —6 94 Female Solitary 2.5 T1a — —7 87 Female Solitary 5 T1b — —8 43 Male Multifocal 0.5-1.0 T1a PRCC, type 1.1 cm —9 54 Male Solitary 2.8 T1a P Ad, 0.2 cm —10 73 Male Solitary 8.5 T2 — —11 61 Male Solitary 1.5 T1a — —12 53 Male Multifocal 0.1-0.5 T1a Multiple PRCC, type 1, 0.5-4 cm —13 54 Male Solitary 3.3 T1a — —14 46 Male Multifocal 0.1-2.4 T1a — —15 53 Female Solitary 8 T3b — TC-RCC 20%; PRCC,

type 2, 80%16 60 Male Solitary 0.6 T1a PRCC, type 2, 4.5 cm —17 60 Male Solitary 1.6 T1a — TC-RCC 80%; PRCC,

type 2, 20%18 77 Male Solitary 2.8 T1a — TC-RCC 70%; PRCC,

type 2, 30%19 55 Male Solitary 4.5 T1b — —20 70 Male Solitary 6.1 T1b PRCC, type 1, 1.1 cm,

5 additional PAdTC-RCC 98%; PRCC,

type 1, 2%

Cases 1 to 13 were reported in (20).P Ad indicates papillary adenoma; PRCC, papillary renal cell carcinoma; TC-RCC, tubulocystic renal cell carcinoma.

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FIGURE 1. Tubulocystic carcinoma with admixed papillary renal cell carcinoma (patient 20). The tumor is a multicystic, sharplycircumscribed mass (A), and is comprised both tubulocystic and papillary components. Both components are admixed together (B).Foamy histiocytes and psammomatous calcification are present in the fibrovascular cores of the papillae (C). Tubulocysticcarcinoma is adjacent to a papillary carcinoma (D).

FIGURE 2. Tubulocystic carcinoma with admixed papillary renal cell carcinoma (patient 15). The tumor comprised 20% oftubulocystic carcinoma and 80% of papillary renal cell carcinoma (A). The cells in papillary renal cell carcinoma (RCC) andtubulocystic RCC have similar morphologic features (B).



cases had a gain of chromosome 17, and 8 of 9 cases had aloss of the Y chromosome. In 2 patients (10 and 14), 2different areas from each tumor had gains of chromo-somes 7 and 17. FISH was performed in 3 cases withconcomitant tubulocystic and papillary components. Inpatient 3, both components had a gain of chromosome7 and a loss of the Y chromosome, but chromosome 17was disomic in both components. In patient 17, bothcomponents had a gain of chromosomes 7 and 17. Inpatient 18, the tubulocystic component was disomic forchromosomes 7 and 17, and the papillary component wasdisomic for chromosome 17, and had a gain of chromo-some 7, but the percentage of cells with chromosome 7gain was low (11%).

Six of 9 cases with all 3 chromosomes assayed hadgains of chromosomes 7 and 17 and loss of the Ychromosome.

ImmunohistochemistryResults of immunostains, including cytokeratin 7,

cytokeratin 19, 34bE12, CD10, AMACR, and PAX-2, on

3 cases with both tubulocystic and papillary componentsare shown in Table 4. The staining patterns for bothcomponents were almost identical in each case.

DISCUSSIONTC-RCC is a peculiar renal tumor with character-

istic gross and microscopic features. Grossly, it is a well-circumscribed multicystic lesion that has been describedas ‘‘Swiss cheese’’ or ‘‘bubble wrap’’-like. Microscopi-cally, it is composed of numerous well-formed tubules andcysts lined with eosinophilic cells with prominent nucleoli.Owing to its unique morphologic features, TC-RCC mayrepresent a distinct subtype of RCC.1,2,20

However, this study has drawn attention to thesimilarity between TC-RCC and another RCC subtype,PRCC. These 2 entities indeed share pathologic andcytogenetic features.

RCCs are usually solitary lesions. Multicentrictumors arising within the same kidney are uncommon

FIGURE 3. Tubulocystic carcinoma with admixed papillary renal cell carcinoma (patient 17). A 1.6-cm tubulocystic carcinoma isadmixed with papillary carcinoma (A). Histiocytes are prominent in the papillary component (B). Both components comprisedidentical oncocytic tumor cells (B and C).



and affect approximately 5% of sporadic renal tumors.5,12

Multicentric lesions are much more common in PRCCthan in other RCC subtypes. In 2 recent studies, each withmore than 1000 patients, multicentricity was observed in12.4% and 17.2% of PRCCs, and only in 3.3% and 3.9%of other renal cancers, including clear-cell, chromophobe,and unclassified types.5,12 In this study, 20% (4/20) ofTC-RCC cases were multicentric. Therefore, TC-RCCsand PRCCs are similar in that they both frequentlyexhibit multicentricity.

If a kidney harbors a multicentric tumor, mosttumor nodules have similar histology. The aforemen-tioned 2 large studies found discordant histology betweentumor nodules in only 0.9% and 1.4% cases.5,12 Incontrast, of the 8 cases with multicentric tumors (eithermultifocal TC-RCC or multifocal TC-RCC and PRCC)in this study, 6 (75%) (cases 1, 3, 8, 12, 16, and 20,Table 1) comprised both TC-RCC and PRCC histology.This incidence (75%) is much higher than that observedin other renal tumors in the general population (0.9% to1.4%).5,12 We also found that the tubulocystic and papillary

RCC components were both present and intimatelyassociated with each other within the same tumor nodulein 4 cases. The tumor cells in both components werecytologically similar. These findings further suggest aclose relationship between TC-RCC and PRCC. A recentstudy of 31 TC-RCCs, however, did not find an associa-tion between TC-RCC and papillary neoplasia.1 Thereason for this discrepancy is not clear. A thoroughexamination of the kidneys harboring TC-RCC is re-quired to ascertain the association between the 2 in futurestudies.

The immunohistochemical profiles of TC-RCC andPRCC are also very similar. The staining was performedon 3 cases with both TC-RCC and PRCC components.AMACR was diffusely and strongly positive in bothTC-RCC and PRCC components in all cases. Otherstains, including PAX-2, CD10, 34bE12, cytokeratin19, and cytokeratin 7, exhibited heterogeneous patternsin different cases. However, the TC-RCC and PRCCcomponents in the same case had identical or very similarstaining patterns for all the markers.

FIGURE 4. Tubulocystic carcinoma with admixed papillary renal cell carcinoma (patient 18). A 2.8-cm tubulocystic carcinoma isadmixed with papillary carcinoma (A). The papillary component comprises papillae lined with cells with abundant granularcytoplasm (B), whereas the tubulocystic component is lined with cuboidal or flattened cells (C). Cells in both components haveidentical nuclear features (D).



Perhaps the most convincing evidence that TC-RCCand PRCC are closely related is from the genetic studies.Using the gene expression microarray analysis, we and

other investigators have established the molecular profilesof clear-cell RCC,9,17,21 papillary RCC,14,20 chromophobeRCC, oncocytoma,13 Wilms’ tumor,16 and medullary

TABLE 2. Chromosome Changes in non-Neoplastic Renal Parenchyma

Chromosome 7 Copy No. Chromosome 17 Copy No. Chromosome Y Copy No.

Diagnosis Case No. 0 1 2 Z3 0 1 2 Z3 0 1

Normal tissue adjacent totubulocystic carcinoma

2 5 15 80 0 3 13 84 0 15 853 7 24 69 2 6 24 70 0 14 867 1 25 74 0 1 28 70 18 3 29 66 2 12 43 45 0 15 859 0 7 93 0 0 4 96 0 18 8210 1 17 82 0 1 16 83 0 15 8513 0 18 91 1 2 17 91 0 20 8014 1 9 89 1 1 10 87 2 26 7417 0 22 70 8 0 35 64 1 16 8418 6 54 37 3 2 47 49 219 0 25 75 0 0 28 72 0 14 8620 0 25 75 0 0 24 76 0

Normal tissue adjacent to PRCC 1 2 13 83 2 0 28 70 22 0 8 87 5 3 7 88 23 2 13 82 3 3 25 72 04 0 15 83 2 0 25 75 05 5 25 70 0 2 37 61 06 4 36 60 0 8 34 58 07 7 31 62 0 17 51 32 08 3 34 63 0 7 26 67 09 0 13 85 2 0 10 90 010 2 8 87 3 0 21 79 011 0 5 95 0 0 9 86 512 0 11 87 2 0 12 85 313 0 18 79 3 0 13 87 014 0 10 90 0 5 24 64 715 0 7 93 0 0 8 89 316 0 19 81 0 3 15 82 017 0 15 85 0 0 18 82 018 0 30 70 0 2 13 83 219 0 18 82 0 2 26 72 020 5 20 75 0 13 22 62 3

Mean+3SD 7 6 29

TABLE 3. Chromosome Changes in Renal Tubulocystic and Papillary Carcinomas

Chromosome Copy Number Chromosome Abnormality

Chromosome 7 Chromosome 17 Chromosome Y Chr 7 Gain Chr 17 Gain Chr Y Loss

Diagnosis Case No. 0 1 2 Z3 0 1 2 Z3 0 1

Tubulocystic carcinoma 2 0 0 31 69 0 0 45 55 40 60 + + +3A* 0 7 82 11 2 14 79 5 34 66 + � +3B* 4 15 53 28 10 38 46 6 38 62 + � +7 4 11 53 32 1 10 64 25 + +8 5 27 56 12 1 48 48 3 14 86 + � �

9 0 5 95 0 0 8 88 4 43 57 � � +10Aw 3 8 33 56 0 1 31 68 39 61 + + +10Bw 8 14 56 22 1 15 62 22 + +13 8 22 57 13 2 16 52 30 50 50 + + +14Aw 0 0 37 63 0 0 28 72 63 37 + + +14Bw 0 1 25 74 0 2 21 77 + +17A* 1 12 66 21 0 11 56 31 39 61 + + +17B* 2 10 68 20 0 1 50 49 35 65 + +18A* 2 29 62 7 2 27 69 2 � �

18B* 3 37 49 11 1 53 43 3 + �

19 1 3 36 60 0 0 20 80 52 48 + + +20 0 10 43 47 0 3 29 68 + +

*A indicates tubulocystic region; B, papillary region.wTwo tubulocystic regions.



FIGURE 5. Trisomy 7 and 17 in renal tubulocystic carcinoma. Fluorescence in situ hybridizations for chromosomes 7 and 17 areperformed on normal adjacent renal tubules (A–C) and tubulocystic carcinoma (D–F). DAPI, a DNA dye, is used to visualize thenuclei (A and D). Most cells in normal tubules have 2 copies of chromosome 7 (B) and chromosome 17 (C), although 1 copy ornone can rarely be seen due to tissue sectioning. Many cells in tubulocystic carcinoma harbor 3 or more copies of chromosomes 7(arrows, E) and 17 (arrows, F).

TABLE 4. Immunohistochemical Profiles of the Tubulocystic and Papillary Renal Cell Carcinoma

Case No. PAX-2 CD10 AMACR 34bE12 Cytokeratin 19 Cytokeratin 7

17 Papillary � + + � � F+Tubulocystic � + + � � F+

18 Papillary � + + F+ F+ F+Tubulocystic � + + F+ F+ F+

20 Papillary + F+ + � � +Tubulocystic + F+ + � � F+

� indicates negative; +, positive; F+, focally positive.



carcinoma.7 We further showed that the molecularclassification of a renal tumor using our comprehensivemolecular signature database of renal cell tumors cor-related strongly with the pathologic diagnosis.19 Owingto very limited availability of tissue for molecular study,we published the gene expression profile of the onlyTC-RCC case in the literature,20 and found that this caseclustered with PRCC and was distinct from other RCCsubtypes, suggesting that TC-RCC is genetically verysimilar to PRCC. A recent study by Amin et al1 foundthat the gene expression profile of 5 TC-RCC cases didnot overlap with that of PRCC determined in investiga-tors’ earlier studies,14,21 although these studies useddifferent input material (formalin-fixed tissue versusfrozen tissue) and array platforms (cDNA array vs.oligonucleotide array) and the results from these studiesmay not be readily comparable with each other.

To further examine the relationship between TC-RCC and PRCC, we studied the cytogenetic alterationsinvolving chromosomes 7, 17, and Y in TC-RCC. Suchdata were not available for TC-RCC but were extensivelystudied for other RCC subtypes in the literature.3 PRCCoften exhibits gains involving chromosomes 7 and 17and loss of the Y chromosome. Although the gain ofchromosome 7 is not specific, gain of chromosome 17 isnot a common feature of non-PRCC tumors and istherefore relatively specific for PRCC.4,6 Using compara-tive genomic microarray analysis, a statistical tool used toinfer the cytogenetic alterations in renal tumors based onthe gene expression patterns, we also showed that PRCCconsistently showed gain of chromosomes 7 and 17.9

Of 34 PRCCs, 79% (27/34) had chromosome 7 gains,whereas 94% (32/34) had chromosome 17 gains.14

Another study showed combined gains of chromosomes7 and 17 in all PRCCs, but in none of the clear-cell orchromophobe RCC cases.7 In this study, we quanti-fied the copy numbers of chromosomes 7, 17, and Y onformalin-fixed and paraffin-embedded tissue sectionsusing FISH. Such a methodology has been usedextensively for cytogenetic studies of RCC (for reviewsee Ref. [3]). To account for the potential artifact as theresult of tissue sectioning (such as nuclear overlapping),we used normal renal tubules as controls and used verystringent criteria for diagnosing trisomy 7 or 17 and lossof the Y chromosome (see Materials and Methods). Tenof 12 TC-RCC cases had gains of chromosome 7, 8 of 12cases had a gain of chromosome 17, and 8 of 9 cases hadloss of the Y chromosome. Six of 9 cases with all 3chromosomes assayed had gains of chromosomes 7 and17 and loss of the Y chromosome.

The patterns of chromosome changes were identicalor very similar between tubulocystic and papillary compo-nents in those cases harboring both components. FISHwas performed in 3 cases with concomitant tubulocysticand papillary RCC components. In patient 3, bothcomponents had a gain of chromosome 7, disomic 17,and a loss of the Y chromosome. In patient 17, bothcomponents had gains of chromosomes 7 and 17. Inpatient 18, the tubulocystic component was disomic for

chromosomes 7 and 17, and the papillary component wasdisomic for chromosome 17, and had a gain of chromo-some 7, although the percentage of cells with chromo-some 7 gain was low (11%). These cytogenetic datastrongly suggest that at least a subset of TC-RCCs sharegenetic features with PRCCs.

Our study raises the possibility that some TC-RCCsmay be a variant of PRCC. Of course, more studies areneeded to confirm the genetic relationship between the 2tumors. This study does not rule out the possibility thatsome TC-RCC cases constitute a unique RCC subtypewith distinct molecular and histologic features. One-thirdof the cases (3/9) in our study did not have cytogeneticchanges characteristic of PRCC. These tumors mayrepresent TC-RCC cases with not fully developedcytogenetic changes or an early form of PRCC. Alter-natively, they may represent a group of tumors entirelydifferent from those TC-RCCs with gains of chromo-somes 7 and 17 and loss of the Y chromosome. Althoughthis group of tumors may be ‘‘true’’ TC-RCC, theycannot be distinguished from other TC-RCCs withtrisomy 7 and 17 based on morphologic and immunohis-tochemical findings.

Our findings raise the question about how to classifyTC-RCC. TC-RCC has distinctive morphologic features.Most TC-RCCs present at stage T1a and have an excel-lent prognosis. Therefore, it warrants a designation as adistinct morphologic entity. Like other investigators,1,2

we classify tumors with pure tubulocystic morphology asTC-RCC. If TC-RCC is found to be associated withPRCC within the same lesion or in the same specimen, weclassify these lesions as ‘‘RCC, unclassified type, withtubulocystic features,’’ as our study suggests these lesionsare closely related to PRCC. These cases can then beflagged for future studies.

The close relationship between TC-RCC and PRCCmay also have important therapeutic implications. TC-RCC can rarely exhibit aggressive clinical behavior withmetastasis to liver and bone.1 Owing to the limitednumber of reports of such cases, there have been noestablished treatment protocols for these patients. Onemight reason that regimens for PRCC may be used foraggressive TC-RCC as the 2 share genetic features.

In summary, this study has provided pathologic andcytogenetic evidence suggesting that TC-RCC and PRCCare closely related entities. With its characteristic grossand microscopic features, TC-RCC may be considered asa unique ‘‘morphologic entity.’’ However, further studiesare needed to document the characteristic molecularfeatures associated with this tumor before it is accepted asa distinct renal cell carcinoma subtype.

ACKNOWLEDGMENTSThe authors thank Dr Howard Levin of Cleveland

Clinic and Dr Gregory MacLennan of Case WesternResearch University Hospitals for critical review andcomments, and Sandra Turner and Mary Beth Hartke fortechnical assistance with FISH assays.



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Renal Tubulocystic Carcinoma Is Closely Related to Papillary Renal Cell Carcinoma: Implications for...

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