RESEARCH ARTICLE
Cystic Renal Oncocytoma and Tubulocystic Renal Cell Carcinoma: Morphologic and Immunohistochemical Comparative Study Faruk Skenderi, MD, MSc,* Monika Ulamec, MD, PhD,w Semir Vranic, MD, PhD,* Nurija Bilalovic, MD, PhD,* Kvetoslava Peckova, MD,z Pavla Rotterova, MD, PhD,z Bohuslava Kokoskova, MD,z Kiril Trpkov, MD,y Pavla Vesela, MD,z Milan Hora, MD, PhD,8 Kristyna Kalusova, MD, MSc,8 Maris Sperga, MD,z Delia Perez Montiel, MD,# Isabel Alvarado Cabrero, MD, PhD,** Stela Bulimbasic, MD, PhD,ww Jindrich Branzovsky, MD,z Michal Michal, MD,z and Ondrej Hes, MD, PhDz zz
Abstract: Renal oncocytoma (RO) may present with a tubulocystic growth in 3% to 7% of cases, and in such cases its morphology may significantly overlap with tubulocystic renal cell carcinoma (TCRCC). We compared the morphologic and immunohistochemical characteristics of these tumors, aiming to clarify the differential diagnostic criteria, which facilitate the discrimination of RO from TCRCC. Twenty-four cystic ROs and 15 TCRCCs were selected and analyzed for: architectural growth patterns, stromal features, cytomorphology, ISUP nucleolar grade, necrosis, and mitotic activity. Immunohistochemical panel included various cytokeratins (AE1-AE3, OSCAR, CAM5.2, CK7), vimentin, CD10, CD117, AMACR, CA-IX, antimitochondrial antigen (MIA), EMA, and Ki-67. The presence of at least focal solid growth and islands of tumor cells interspersed with loose stroma, lower ISUP nucleolar grade, absence of necrosis, and absence of mitotic figures were strongly suggestive of a cystic RO. In contrast, the absence of solid and island growth patterns and presence of more compact, fibrous stroma, accomReceived for publication August 26, 2014; accepted October 1, 2014. From the *Department of Pathology and Cytology, Clinical Center of the University of Sarajevo, Sarajevo, Bosnia and Herzegovina; wLjudevit Jurak Department of Pathology, Sestre milosrdnice Clinical Hospital Center; wwDepartment of Pathology, University Hospital Dubrava, Zagreb, Croatia; Departments of zPathology; 8Urology, Charles University, Faculty of Medicine and University Hospital Plzenˇ; zzBiomedical Centre, Faculty of Medicine in Plzen, Charles University in Prague, Plzen, Czech Republic; yDepartment of Pathology and Laboratory Medicine, Calgary Laboratory Services and University of Calgary, Calgary, AB, Canada; zDepartment of Pathology, East University Riga, Riga, Latvia; #Department of Pathology, Institute Nacional de Cancerologia; and **Department of Pathology, Centro Medico, Mexico City, Mexico. Supported by the Charles University Research Fund (project number P36) and by the project CZ.1.05/2.1.00/03.0076 from European Regional Development Fund. The authors declare no conflict of interest. Reprints: Ondrej Hes, MD, PhD, Department of Pathology, Medical Faculty and Charles University Hospital Plzen, Charles University, Alej Svobody 80, 304 60 Pilsen, Czech Republic (e-mail: hes@ medima.cz). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
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panied by higher ISUP nucleolar grade, focal necrosis, and mitotic figures were all associated with TCRCC. TCRCC marked more frequently for vimentin, CD10, AMACR, and CK7 and had a higher proliferative index by Ki-67 (> 15%). CD117 was negative in 14/15 cases. One case was weakly CD117 reactive with cytoplasmic positivity. All cystic RO cases were strongly positive for CD117. The remaining markers (AE1-AE3, CAM5.2, OSCAR, CA-IX, MIA, EMA) were of limited utility. Presence of tumor cell islands and solid growth areas and the type of stroma may be major morphologic criteria in differentiating cystic RO from TCRCC. In difficult cases, or when a limited tissue precludes full morphologic assessment, immunohistochemical pattern of vimentin, CD10, CD117, AMACR, CK7, and Ki-67 could help in establishing the correct diagnosis. Key Words: kidney, renal oncocytoma, tubulocystic renal cell carcinoma, overlap, immunohistochemistry (Appl Immunohistochem Mol Morphol 2016;24:112–119)
R
enal oncocytoma (RO) is considered a benign renal neoplasm originating from the intercalated cells. It comprises approximately 5% of all renal tumors and has an excellent prognosis.1 RO is known for its variations in architecture and cytology, and several renal neoplasms may mimic RO, such as chromophobe renal cell carcinoma, oncocytic variant of papillary renal cell carcinoma, granular cell variant of clear cell renal cell carcinoma, or hybrid oncocytic/chromophobe tumors.2–5 Less frequently (3% to 7%), RO may exhibit a pattern composed of tubules and cysts, combined with a variable component of small cell islands, with a background of loose or hypocellular stroma.6–9 Tubulocystic renal cell carcinoma (TCRCC) has been recently recognized as a distinct entity by the International Society of Urological Pathology (ISUP) Vancouver Classification.10 TCRCC is composed of tubules and cysts of variable size and scant fibrous stroma. The cysts are lined by 1 or more epithelial cell layers, which demonstrate abundant eosinophilic
Appl Immunohistochem Mol Morphol
Volume 24, Number 2, February 2016
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
Appl Immunohistochem Mol Morphol
Volume 24, Number 2, February 2016
cytoplasm and prominent nucleoli.11 The overlapping morphologic features of the cystic variant of RO (CRO) and TCRCC may represent a diagnostic challenge, particularly when limited tissue sample is available for assessment. RO is considered a benign tumor despite the presence of atypical features.6,9,12–14 In contrast, TCRCC represents a low-grade carcinoma, which sometimes may demonstrate an aggressive behavior. Therefore, the distinction and the correct diagnosis of these tumors are of clinical relevance and impact the patient prognosis and management. In this study, we compared the morphologic and immunohistochemical (IHC) characteristics of CRO and TCRCC, with an aim to clarify the diagnostic and the differential diagnostic features of these tumors.
MATERIALS AND METHODS Case Selection Twenty-four CRO with at least 50% of the tumor demonstrating tubulocystic architecture have been selected from a total of 645 ROs (3.7% of available RO). CRO otherwise showed morphology of round-to-polygonal cells with finely granular, eosinophilic cytoplasm with round to oval nuclei consistent with diagnosis of RO. Fifteen TCRCCs have also been retrieved from the in-house and consultation files of the same registry. TCRCC typically demonstrated well-formed, small to medium-sized tubules and cysts, lined by large cells, usually demonstrating abundant eosinophilic cytoplasm. The lining cells showed focal hob-nail shape with high nuclear grade with prominent nucleoli. For each case, 1 to 49 tissue blocks (mean 5.6) were available for review. The diagnosis was rendered by 3 pathologists (F.S., M.U., O.H.) and was supported by the IHC analysis. The tissue was fixed in 4% buffered formalin, embedded routinely into paraffin, and 5 mm sections were cut and stained with hematoxylin and eosin. The sections were evaluated by light microscopy for the following histologic features: visually estimated percentage of cystic, solid, and island patterns, epithelial lining of the cysts (single, pseudopapillary, multilayered), presence of papillary protrusions in the cysts, hemorrhage within the cysts or stroma, extent and composition of the stroma, cytologic features including nuclear ISUP nucleolar grade, mitotic activity, and presence of microscopic necrosis.
IHC IHC examination was performed in 37 of 39 cases. Only selected markers were stained in 2 ROs and 2 TCRCCs because of limited tissue availability. Assays were performed using the Ventana Benchmark XT automated stainer (Ventana Medical System Inc., Tucson, AZ). The following primary antibodies were used: epithelial membrane antigen (EMA) (E29, monoclonal; Dako, Carpinteria, CA; 1:1000), cytokeratins (CAM5.2, monoclonal; Becton-Dickinson, San Jose, CA; 1:200), Pan Ab-1 (AE1-AE3, monoclonal; BioGenex, San Ramon, CA; 1:1000), cytokeratin 7 (OV-TL12/30, Copyright
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2014 Wolters Kluwer Health, Inc. All rights reserved.
Renal Oncocytoma and Tubulocystic RCC
monoclonal; Dako; 1:200), cytokeratin OSCAR (OSCAR, monoclonal; Covance, Princetown, NJ; 1:2000), racemase/AMACR (P504S, monoclonal; Zeta, Sierra Madre, CA, 1:50), vimentin (D9, monoclonal; NeoMarkers, Westinghouse, CA; 1:1000), Ki-67 (MIB1, monoclonal; Dako, Glostrup, Denmark; 1:1000), carbonic anhydrase IX (CA-IX; rhCA9, monoclonal; RD systems, Abingdon, GB; 1:100), antimitochondrial antigen (MIA, monoclonal; BioGenex; 1:100). CD10 (56C6, monoclonal; Novocastra, Newcastle, UK; 1:50), c-kit (CD117, polyclonal; DakoCytomation, Glostrup, Denmark; RTU). Appropriate positive and negative controls were used for all IHC assays. The pattern of staining was scored negative, if no staining was observed; scattered positive, if single or few cells were clearly positive throughout the tumor; focal positive, if large groups of cells were clearly positive (< 50%); and diffuse positive, if majority (> 50%) of tumor cells were positive.
Statistical Analysis The data were analyzed using SPSS version 19 (Chicago, IL). w2 test was used to analyze the differences regarding the morphologic criteria and IHC staining patterns and intensity. The Fisher exact test was used for dichotomous variables and Student t test was used to compare mean Ki-67 percentages. P value of 0.05
< 0.001
< 0.001
< 0.001
< 0.001
(57) (0) (36) (7) (0) (0) (7.7) (92.3)
3/13 (23) 0/13 (0) 5/13 (38.5) 5/13 (35.5) 17.93
0.03
0.71
0.52 0.001
P < 0.05 was considered significant. AMACR indicates a-methylacyl-CoA racemase; CA-IX, carbonic anhydrase 9; EMA, epithelial membrane antigen; MIA, antimitochondrial antigen.
limited in TCRCC and may also help differentiate between these tumors. The type of intervening stroma can be another helpful morphologic feature, because loose stroma was regularly seen in CRO, whereas TCRCC usually contained fibrotic and more compact stromal component. In addition, no mitotic figures were found in Copyright
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2014 Wolters Kluwer Health, Inc. All rights reserved.
any of the CROs and the majority of them demonstrated lower nucleolar grades (1 or 2). In contrast, TCRCC showed focal mitotic figures in about a quarter of the cases and nucleolar grade 3 was present in 60% of TCRCC. Microscopic necrosis was not seen in any CRO, but was found in about a third of TCRCC. www.appliedimmunohist.com |
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FIGURE 4. Markers useful for differential diagnosis between CRO and TCRCC. CD117 was positive in all the CRO cases, whereas negative in all but 1 case of TCRCC. CK7, vimentin, CD10, and AMACR were negative or scattered positive in majority of CRO cases, whereas they were focally or diffusely positive in most of the TCRCC cases. CRO indicates cystic renal oncocytoma; TCRCC, tubulocystic renal cell carcinoma; ***P < 0.001.
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The development of radiologically guided percutaneous needle biopsies, which provide small amounts of tissue or cellular material for assessment of renal masses, has introduced novel diagnostic challenges for the pathologist. In such circumstances, many morphologic features may not be available for assessment in the limited tissue and the ancillary IHC may help establish the correct diagnosis. In this study, none of the evaluated antibodies showed exclusive specificity for either CRO or TCRCC, although CD117 was highly discriminative, as all CROs were diffusely positive, whereas only 1 case of TCRCC showed weak cytoplasmic staining. We found TCRCC to be more frequently positive for vimentin, CD10, AMACR, and CK7 and had a higher proliferative index by Ki-67 (> 15%). Vimentin was very useful, as it was either negative or scattered cell positive in CRO, in contrast to TCRCC, in which it was strongly and diffusely expressed. Pattern of vimentin positivity in RO was described in detail by Hes et al in 2007. In their series, 72.6% of RO showed scattered strong positivity (single cells or small groups of cells).14 Vimentin positivity is described as diffuse in all TCRCCs.23,24 Results of our study are in concordance with above-mentioned data (55% of CRO with scattered positivity and 84.6% of TCRCC with diffuse strong positivity). CD10 and AMACR were both often negative in CRO, whereas diffuse or focal positivity was observed in TCRCC. CRO also consistently expressed CK7 in an isolated cells or scattered pattern, much less than observed in TCRCC. Proliferation activity in CRO was also lower (< 5% cells), whereas TCRCC demonstrated higher expression (> 15% cells). CA-IX was of limited utility as it was predominantly negative in both TCRCC and CRO. The remaining markers (AE1/AE3, CAM5.2, OSCAR, MIA, EMA) were also of limited diagnostic value. Performing additional studies for differentiation of these tumors, including genetic and molecular, may rarely be necessary, but it may be helpful in most difficult cases. Cytogenetic changes found most frequently in RO include losses of chromosome 1 or Y and balanced translocation of the 11q13 breakpoint region.9 Most frequent cytogenetic change in TCRCC includes gain of chromosome 7, although occasionally gains of both chromosomes 7 and 17 may occur.11 In conclusion, although CRO and TCRCC may present with significantly overlapping morphology, a careful morphologic assessment for the presence of solid tumor growth or islands, the type of tumor stroma, nucleolar grade, mitotic activity, and necrosis, and aided by a limited immunopanel that includes vimentin, CD10, CD117, AMACR, CK7, and Ki-67, will lead to establishing a correct diagnosis. This is important to bear in mind when faced with limited material (core biopsy or inadequate sampling) from a lowgrade renal neoplasm composed of oncocytic cells arranged in a predominantly tubulary pattern. REFERENCES
FIGURE 5. Immunoreactivity for vimentin in CRO (A) and TCRCC (B) showing diffuse positivity in TRCC and negative staining in cells of CRO (vimentin, clone D9).
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1. Eble JN, Sauter G, Epstein A, et al. Pathology and Genetics. Tumors of the Urinary System and Male Genital Organs. Lyon: IARC Press; 2004. 2. Kuroda N, Tanaka A, Yamaguchi T, et al. Chromophobe renal cell carcinoma, oncocytic variant: a proposal of a new variant giving a
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3.
4. 5.
6. 7. 8. 9. 10. 11. 12.
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critical diagnostic pitfall in diagnosing renal oncocytic tumors. Med Mol Morphol. 2013;46:49–55. Hes O, Brunelli M, Michal M, et al. Oncocytic papillary renal cell carcinoma: a clinicopathologic, immunohistochemical, ultrastructural, and interphase cytogenetic study of 12 cases. Ann Diagn Pathol. 2006;10:133–139. Mai KT, Kohler DM, Robertson SJ, et al. Oncocytic papillary renal cell carcinoma with solid architecture: mimic of renal oncocytoma. Pathol Int. 2008;58:164–168. Petersson F, Gatalica Z, Grossmann P, et al. Sporadic hybrid oncocytic/chromophobe tumor of the kidney: a clinicopathologic, histomorphologic, immunohistochemical, ultrastructural, and molecular cytogenetic study of 14 cases. Virchows Arch. 2010;456: 355–365. Amin MB, Crotty TB, Tickoo SK, et al. Renal oncocytoma: a reappraisal of morphologic features with clinicopathologic findings in 80 cases. Am J Surg Pathol. 1997;21:1–12. Xiao GQ, Ko HB, Unger P. Telangiectatic oncocytoma: a previously undescribed variant of renal oncocytoma. Am J Clin Pathol. 2013;140:103–108. Kuroda N, Toi M, Hiroi M, et al. Review of renal oncocytoma with focus on clinical and pathobiological aspects. Histol Histopathol. 2003;18:935–942. Trpkov K, Yilmaz A, Uzer D, et al. Renal oncocytoma revisited: a clinicopathological study of 109 cases with emphasis on problematic diagnostic features. Histopathology. 2010;57:893–906. Srigley JR, Delahunt B, Eble JN, et al. The International Society of Urological Pathology (ISUP) Vancouver classification of renal neoplasia. Am J Surg Pathol. 2013;37:1469–1489. Yang XJ, Zhou M, Hes O, et al. Tubulocystic carcinoma of the kidney: clinicopathologic and molecular characterization. Am J Surg Pathol. 2008;32:177–187. Petersson F, Sima R, Grossmann P, et al. Renal small cell oncocytoma with pseudorosettes: a histomorphologic, immunohistochemical, and molecular genetic study of 10 cases. Hum Pathol. 2011;42:1751–1760.
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13. Hes O, Michal M, Boudova L, et al. Small cell variant of renal oncocytoma—a rare and misleading type of benign renal tumor. Int J Surg Pathol. 2001;9:215–222. 14. Hes O, Michal M, Kuroda N, et al. Vimentin reactivity in renal oncocytoma: immunohistochemical study of 234 cases. Arch Pathol Lab Med. 2007;131:1782–1788. 15. Amin R, Anthony P. Metastatic renal oncocytoma: a case report and review of the literature. Clin Oncol. 1999;11:277–279. 16. Oxley JD, Sullivan J, Mitchelmore A, et al. Metastatic renal oncocytoma. J Clin Pathol. 2007;60:720–722. 17. Perez-Ordonez B, Hamed G, Campbell S, et al. Renal oncocytoma: a clinicopathologic study of 70 cases. Am J Surg Pathol. 1997;21: 871–883. 18. Arguelles Salido E, Marcilla Plaza D, Medina Lopez R, et al. Renal oncocytoma. Review of our 22 patients. Actas Urol Esp. 2006;30: 583–590. 19. MacLennan GT, Farrow GM, Bostwick DG. Low-grade collecting duct carcinoma of the kidney: report of 13 cases of low-grade mucinous tubulocystic renal carcinoma of possible collecting duct origin. Urology. 1997;50:679–684. 20. MacLennan GT, Bostwick DG. Tubulocystic carcinoma, mucinous tubular and spindle cell carcinoma, and other recently described rare renal tumors. Clin Lab Med. 2005;25:393–416. 21. Hora M, Urge T, Eret V, et al. Tubulocystic renal carcinoma: a clinical perspective. World J Urol. 2011;29:349–354. 22. Bhullar JS, Varshney N, Bhullar AK, et al. A new type of renal cancer—tubulocystic carcinoma of the kidney: a review of the literature. Int J Surg Pathol. 2013;22:297–302. 23. Skinnider BF, Folpe AL, Hennigar RA, et al. Distribution of cytokeratins and vimentin in adult renal neoplasms and normal renal tissue: potential utility of a cytokeratin antibody panel in the differential diagnosis of renal tumors. Am J Surg Pathol. 2005;29: 747–754. 24. Alexiev BA, Drachenberg CB. Tubulocystic carcinoma of the kidney: a histologic, immunohistochemical, and ultrastructural study. Virchows Arch. 2013;462:575–581.
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Cystic Renal Oncocytoma and Tubulocystic Renal Cell Carcinoma: Morphologic and Immunohistochemical Comparative Study Faruk Skenderi, MD, MSc,* Monika Ulamec, MD, PhD,w Semir Vranic, MD, PhD,* Nurija Bilalovic, MD, PhD,* Kvetoslava Peckova, MD,z Pavla Rotterova, MD, PhD,z Bohuslava Kokoskova, MD,z Kiril Trpkov, MD,y Pavla Vesela, MD,z Milan Hora, MD, PhD,8 Kristyna Kalusova, MD, MSc,8 Maris Sperga, MD,z Delia Perez Montiel, MD,# Isabel Alvarado Cabrero, MD, PhD,** Stela Bulimbasic, MD, PhD,ww Jindrich Branzovsky, MD,z Michal Michal, MD,z and Ondrej Hes, MD, PhDz zz
Abstract: Renal oncocytoma (RO) may present with a tubulocystic growth in 3% to 7% of cases, and in such cases its morphology may significantly overlap with tubulocystic renal cell carcinoma (TCRCC). We compared the morphologic and immunohistochemical characteristics of these tumors, aiming to clarify the differential diagnostic criteria, which facilitate the discrimination of RO from TCRCC. Twenty-four cystic ROs and 15 TCRCCs were selected and analyzed for: architectural growth patterns, stromal features, cytomorphology, ISUP nucleolar grade, necrosis, and mitotic activity. Immunohistochemical panel included various cytokeratins (AE1-AE3, OSCAR, CAM5.2, CK7), vimentin, CD10, CD117, AMACR, CA-IX, antimitochondrial antigen (MIA), EMA, and Ki-67. The presence of at least focal solid growth and islands of tumor cells interspersed with loose stroma, lower ISUP nucleolar grade, absence of necrosis, and absence of mitotic figures were strongly suggestive of a cystic RO. In contrast, the absence of solid and island growth patterns and presence of more compact, fibrous stroma, accomReceived for publication August 26, 2014; accepted October 1, 2014. From the *Department of Pathology and Cytology, Clinical Center of the University of Sarajevo, Sarajevo, Bosnia and Herzegovina; wLjudevit Jurak Department of Pathology, Sestre milosrdnice Clinical Hospital Center; wwDepartment of Pathology, University Hospital Dubrava, Zagreb, Croatia; Departments of zPathology; 8Urology, Charles University, Faculty of Medicine and University Hospital Plzenˇ; zzBiomedical Centre, Faculty of Medicine in Plzen, Charles University in Prague, Plzen, Czech Republic; yDepartment of Pathology and Laboratory Medicine, Calgary Laboratory Services and University of Calgary, Calgary, AB, Canada; zDepartment of Pathology, East University Riga, Riga, Latvia; #Department of Pathology, Institute Nacional de Cancerologia; and **Department of Pathology, Centro Medico, Mexico City, Mexico. Supported by the Charles University Research Fund (project number P36) and by the project CZ.1.05/2.1.00/03.0076 from European Regional Development Fund. The authors declare no conflict of interest. Reprints: Ondrej Hes, MD, PhD, Department of Pathology, Medical Faculty and Charles University Hospital Plzen, Charles University, Alej Svobody 80, 304 60 Pilsen, Czech Republic (e-mail: hes@ medima.cz). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
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panied by higher ISUP nucleolar grade, focal necrosis, and mitotic figures were all associated with TCRCC. TCRCC marked more frequently for vimentin, CD10, AMACR, and CK7 and had a higher proliferative index by Ki-67 (> 15%). CD117 was negative in 14/15 cases. One case was weakly CD117 reactive with cytoplasmic positivity. All cystic RO cases were strongly positive for CD117. The remaining markers (AE1-AE3, CAM5.2, OSCAR, CA-IX, MIA, EMA) were of limited utility. Presence of tumor cell islands and solid growth areas and the type of stroma may be major morphologic criteria in differentiating cystic RO from TCRCC. In difficult cases, or when a limited tissue precludes full morphologic assessment, immunohistochemical pattern of vimentin, CD10, CD117, AMACR, CK7, and Ki-67 could help in establishing the correct diagnosis. Key Words: kidney, renal oncocytoma, tubulocystic renal cell carcinoma, overlap, immunohistochemistry (Appl Immunohistochem Mol Morphol 2016;24:112–119)
R
enal oncocytoma (RO) is considered a benign renal neoplasm originating from the intercalated cells. It comprises approximately 5% of all renal tumors and has an excellent prognosis.1 RO is known for its variations in architecture and cytology, and several renal neoplasms may mimic RO, such as chromophobe renal cell carcinoma, oncocytic variant of papillary renal cell carcinoma, granular cell variant of clear cell renal cell carcinoma, or hybrid oncocytic/chromophobe tumors.2–5 Less frequently (3% to 7%), RO may exhibit a pattern composed of tubules and cysts, combined with a variable component of small cell islands, with a background of loose or hypocellular stroma.6–9 Tubulocystic renal cell carcinoma (TCRCC) has been recently recognized as a distinct entity by the International Society of Urological Pathology (ISUP) Vancouver Classification.10 TCRCC is composed of tubules and cysts of variable size and scant fibrous stroma. The cysts are lined by 1 or more epithelial cell layers, which demonstrate abundant eosinophilic
Appl Immunohistochem Mol Morphol
Volume 24, Number 2, February 2016
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
Appl Immunohistochem Mol Morphol
Volume 24, Number 2, February 2016
cytoplasm and prominent nucleoli.11 The overlapping morphologic features of the cystic variant of RO (CRO) and TCRCC may represent a diagnostic challenge, particularly when limited tissue sample is available for assessment. RO is considered a benign tumor despite the presence of atypical features.6,9,12–14 In contrast, TCRCC represents a low-grade carcinoma, which sometimes may demonstrate an aggressive behavior. Therefore, the distinction and the correct diagnosis of these tumors are of clinical relevance and impact the patient prognosis and management. In this study, we compared the morphologic and immunohistochemical (IHC) characteristics of CRO and TCRCC, with an aim to clarify the diagnostic and the differential diagnostic features of these tumors.
MATERIALS AND METHODS Case Selection Twenty-four CRO with at least 50% of the tumor demonstrating tubulocystic architecture have been selected from a total of 645 ROs (3.7% of available RO). CRO otherwise showed morphology of round-to-polygonal cells with finely granular, eosinophilic cytoplasm with round to oval nuclei consistent with diagnosis of RO. Fifteen TCRCCs have also been retrieved from the in-house and consultation files of the same registry. TCRCC typically demonstrated well-formed, small to medium-sized tubules and cysts, lined by large cells, usually demonstrating abundant eosinophilic cytoplasm. The lining cells showed focal hob-nail shape with high nuclear grade with prominent nucleoli. For each case, 1 to 49 tissue blocks (mean 5.6) were available for review. The diagnosis was rendered by 3 pathologists (F.S., M.U., O.H.) and was supported by the IHC analysis. The tissue was fixed in 4% buffered formalin, embedded routinely into paraffin, and 5 mm sections were cut and stained with hematoxylin and eosin. The sections were evaluated by light microscopy for the following histologic features: visually estimated percentage of cystic, solid, and island patterns, epithelial lining of the cysts (single, pseudopapillary, multilayered), presence of papillary protrusions in the cysts, hemorrhage within the cysts or stroma, extent and composition of the stroma, cytologic features including nuclear ISUP nucleolar grade, mitotic activity, and presence of microscopic necrosis.
IHC IHC examination was performed in 37 of 39 cases. Only selected markers were stained in 2 ROs and 2 TCRCCs because of limited tissue availability. Assays were performed using the Ventana Benchmark XT automated stainer (Ventana Medical System Inc., Tucson, AZ). The following primary antibodies were used: epithelial membrane antigen (EMA) (E29, monoclonal; Dako, Carpinteria, CA; 1:1000), cytokeratins (CAM5.2, monoclonal; Becton-Dickinson, San Jose, CA; 1:200), Pan Ab-1 (AE1-AE3, monoclonal; BioGenex, San Ramon, CA; 1:1000), cytokeratin 7 (OV-TL12/30, Copyright
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2014 Wolters Kluwer Health, Inc. All rights reserved.
Renal Oncocytoma and Tubulocystic RCC
monoclonal; Dako; 1:200), cytokeratin OSCAR (OSCAR, monoclonal; Covance, Princetown, NJ; 1:2000), racemase/AMACR (P504S, monoclonal; Zeta, Sierra Madre, CA, 1:50), vimentin (D9, monoclonal; NeoMarkers, Westinghouse, CA; 1:1000), Ki-67 (MIB1, monoclonal; Dako, Glostrup, Denmark; 1:1000), carbonic anhydrase IX (CA-IX; rhCA9, monoclonal; RD systems, Abingdon, GB; 1:100), antimitochondrial antigen (MIA, monoclonal; BioGenex; 1:100). CD10 (56C6, monoclonal; Novocastra, Newcastle, UK; 1:50), c-kit (CD117, polyclonal; DakoCytomation, Glostrup, Denmark; RTU). Appropriate positive and negative controls were used for all IHC assays. The pattern of staining was scored negative, if no staining was observed; scattered positive, if single or few cells were clearly positive throughout the tumor; focal positive, if large groups of cells were clearly positive (< 50%); and diffuse positive, if majority (> 50%) of tumor cells were positive.
Statistical Analysis The data were analyzed using SPSS version 19 (Chicago, IL). w2 test was used to analyze the differences regarding the morphologic criteria and IHC staining patterns and intensity. The Fisher exact test was used for dichotomous variables and Student t test was used to compare mean Ki-67 percentages. P value of 0.05
< 0.001
< 0.001
< 0.001
< 0.001
(57) (0) (36) (7) (0) (0) (7.7) (92.3)
3/13 (23) 0/13 (0) 5/13 (38.5) 5/13 (35.5) 17.93
0.03
0.71
0.52 0.001
P < 0.05 was considered significant. AMACR indicates a-methylacyl-CoA racemase; CA-IX, carbonic anhydrase 9; EMA, epithelial membrane antigen; MIA, antimitochondrial antigen.
limited in TCRCC and may also help differentiate between these tumors. The type of intervening stroma can be another helpful morphologic feature, because loose stroma was regularly seen in CRO, whereas TCRCC usually contained fibrotic and more compact stromal component. In addition, no mitotic figures were found in Copyright
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2014 Wolters Kluwer Health, Inc. All rights reserved.
any of the CROs and the majority of them demonstrated lower nucleolar grades (1 or 2). In contrast, TCRCC showed focal mitotic figures in about a quarter of the cases and nucleolar grade 3 was present in 60% of TCRCC. Microscopic necrosis was not seen in any CRO, but was found in about a third of TCRCC. www.appliedimmunohist.com |
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FIGURE 4. Markers useful for differential diagnosis between CRO and TCRCC. CD117 was positive in all the CRO cases, whereas negative in all but 1 case of TCRCC. CK7, vimentin, CD10, and AMACR were negative or scattered positive in majority of CRO cases, whereas they were focally or diffusely positive in most of the TCRCC cases. CRO indicates cystic renal oncocytoma; TCRCC, tubulocystic renal cell carcinoma; ***P < 0.001.
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The development of radiologically guided percutaneous needle biopsies, which provide small amounts of tissue or cellular material for assessment of renal masses, has introduced novel diagnostic challenges for the pathologist. In such circumstances, many morphologic features may not be available for assessment in the limited tissue and the ancillary IHC may help establish the correct diagnosis. In this study, none of the evaluated antibodies showed exclusive specificity for either CRO or TCRCC, although CD117 was highly discriminative, as all CROs were diffusely positive, whereas only 1 case of TCRCC showed weak cytoplasmic staining. We found TCRCC to be more frequently positive for vimentin, CD10, AMACR, and CK7 and had a higher proliferative index by Ki-67 (> 15%). Vimentin was very useful, as it was either negative or scattered cell positive in CRO, in contrast to TCRCC, in which it was strongly and diffusely expressed. Pattern of vimentin positivity in RO was described in detail by Hes et al in 2007. In their series, 72.6% of RO showed scattered strong positivity (single cells or small groups of cells).14 Vimentin positivity is described as diffuse in all TCRCCs.23,24 Results of our study are in concordance with above-mentioned data (55% of CRO with scattered positivity and 84.6% of TCRCC with diffuse strong positivity). CD10 and AMACR were both often negative in CRO, whereas diffuse or focal positivity was observed in TCRCC. CRO also consistently expressed CK7 in an isolated cells or scattered pattern, much less than observed in TCRCC. Proliferation activity in CRO was also lower (< 5% cells), whereas TCRCC demonstrated higher expression (> 15% cells). CA-IX was of limited utility as it was predominantly negative in both TCRCC and CRO. The remaining markers (AE1/AE3, CAM5.2, OSCAR, MIA, EMA) were also of limited diagnostic value. Performing additional studies for differentiation of these tumors, including genetic and molecular, may rarely be necessary, but it may be helpful in most difficult cases. Cytogenetic changes found most frequently in RO include losses of chromosome 1 or Y and balanced translocation of the 11q13 breakpoint region.9 Most frequent cytogenetic change in TCRCC includes gain of chromosome 7, although occasionally gains of both chromosomes 7 and 17 may occur.11 In conclusion, although CRO and TCRCC may present with significantly overlapping morphology, a careful morphologic assessment for the presence of solid tumor growth or islands, the type of tumor stroma, nucleolar grade, mitotic activity, and necrosis, and aided by a limited immunopanel that includes vimentin, CD10, CD117, AMACR, CK7, and Ki-67, will lead to establishing a correct diagnosis. This is important to bear in mind when faced with limited material (core biopsy or inadequate sampling) from a lowgrade renal neoplasm composed of oncocytic cells arranged in a predominantly tubulary pattern. REFERENCES
FIGURE 5. Immunoreactivity for vimentin in CRO (A) and TCRCC (B) showing diffuse positivity in TRCC and negative staining in cells of CRO (vimentin, clone D9).
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