Distinctive renal cell tumor simulating atrophic kidney with 2 types of microcalcifications. Report of 3 cases ☆ , ☆☆ Ondrej Hes, MD, PhD a, b , Tulio Geraldo de Souza, MD c , Kristyna Pivovarcikova, MUC a , Petr Grossmann, PhD a , Petr Martinek, MSc a , Naoto Kuroda, MD d , Denisa Kacerovska, MD, PhD a , Marian Svajdler, MD e , Lubomir Straka, MD f , Fredrik Petersson, MD, PhD g , Milan Hora, MD, PhD b, h , Michal Michal, MD a, ⁎ a Department of Pathology, Faculty of Medicine in Plzeň, Charles University in Prague, Pilsen, Czech Republic b Biomedical Centre, Faculty of Medicine in Plzeň, Charles University in Prague, Pilsen, Czech Republic c Department of Pathology, Hospital Aliança, Salvador, Bahia, Brazil d Department of Pathology, Red Cross Hospital Kochi, Kochi, Japan e Department of Pathology, Pasteur University Hospital Kosice, Kosice, Slovak Republic f Klinicka Patologia Presov, Presov, Slovak Republic g Department of Pathology, National University Health System, Singapore, Singapore h Department of Urology, Faculty of Medicine in Plzeň, Charles University in Prague, Pilsen, Czech Republic abstract article info Keywords: Kidney Atrophic renal parenchyma-like tumor Thyroid-like renal tumor Comparative genomic hybridization HUMARA We report 3 cases of primary renal cell tumor simulating atrophic kidney with distinct gross, morphologic, immunohistochemical, and molecular genetic features. The tumors were retrieved out of more than 17 000 renal tumors from the Plzen Tumor Registry. Tissues for light microscopy had been fixed, embedded, and stained with hematoxylin and eosin using routine procedures. The tumors were further analyzed using immunohistochemistry, array comparative genomic hybridization, and human androgen receptor. Analyses of VHL gene and loss of heterozygosity (LOH) 3p were also performed. The patients were 2 women and 1 man, with ages ranging from 29 to 35 years (mean, 31.3 years). Grossly, the neoplasms were encapsulated and round with largest diameter of 3.5 cm (mean, 3.2 cm). Follow-up available for all patients ranged from 2 to 14 years (mean, 8 years). No aggressive behavior was noted. Histologically, akin to atrophic (postpyelonephritic) kidney parenchyma, the tumors were composed of follicles of varying sizes that were filled by eosinophilic secretion. Rare areas contained collapsed follicles. Each follicle was endowed with a small capillary. The stroma was loose, inconspicuous, and focally fibrotic. Two types of calcifications were noted: typical psammoma bodies and amorphous dark-blue stained calcified deposits. Immunohistochemically, tumors were strongly positive for cytokeratins (OSCAR), CD10, and vimentin, with weak immunopositivity for CAM5.2 and AE1-AE3. WT1 and cathepsin K were weakly to moderately focally to diffusely positive. Tumors were negative for cytokeratin 20, carbonic anhydrase IX, parvalbumin, HMB45, TTF1, TFE3, chromogranin A, thyroglobulin, PAX8, and ALK. Only 1 case was suitable for molecular genetic analyses. No mutations were found in the VHL gene; no methylation of VHL promoter was noted. No numerical aberrations were found by array comparative genomic hybridization analysis. LOH for chromosome 3p was not detected. Analysis of clonality (human androgen receptor) revealed the monoclonal nature of the tumor. We describe an unknown tumor of the kidney that (1) resembles renal atrophic kidney or nodular goiter of thyroidal gland; (2) contains a leiomyomatous capsule and 2 types of calcifications; (3) lacks mitoses, atypias, necroses, and hemorrhages and nearly lack Ki-67 positivity; and (4) so far showed benign biological behavior. © 2014 Elsevier Inc. All rights reserved. 1. Introduction We report 3 cases of a primary renal cell tumor microscopically simulating atrophic kidney with distinct gross, morphologic, and immunohistochemical features, which has not so far been reported, to the best of our knowledge. Comparative genomic hybridization (CGH) analysis and analysis of clonality using X-chromosomal inactivation pattern and human androgen receptor (HUMARA) locus were used to better understand the nature of this tumor and to distinguish it from the kidney with atrophic changes. Annals of Diagnostic Pathology 18 (2014) 82–88 ☆ The study was supported by the Charles University Research Fund (project number P36), by the project CZ.1.05/2.1.00/03.0076 from European Regional Develop- ment Fund, and by Charles University Fund SVV 06805. ☆☆ Conflict of interest statement: The authors declare that they have no conflict of interest. ⁎ Corresponding author at: Department of Pathology, Medical Faculty and Charles University Hospital Plzen, Charles University, Alej Svobody 80, 304 60 Pilsen, Czech Republic. E-mail address: michal@medima.cz (M. Michal). 1092-9134/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.anndiagpath.2013.12.003 Contents lists available at ScienceDirect Annals of Diagnostic Pathology