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Renal small cell oncocytoma with pseudorosettes: A histomorphologic, immunihistochemical and molecular genetic study of 10 cases

Abstract:

A cohort of a heretofore not described rare subtype of renal oncocytoma, small cell oncocytoma with pseudorosettes is presented. Patients were 6 women and 4 men with ages ranging from 51 to 76 years. The tumors displayed areas composed of small cells (“oncoblasts”) featuring scant cytoplasm and small, round monomorphic nuclei. The small cell areas constituted 15% to 60% of the total tumor volume (mean, 28.5%; median, 22.5%). No necrosis or mitotic activity was discerned. All tumors also contained areas composed of characteristic oncocytes comprising 40% to 85% of the total tumor volume. In all cases, a varying number of pseudorosettes were identified. The pseudorosettes were composed of small globules of (periodic acid–Schiff–positive) hyaline basal membrane–like material surrounded by small “oncoblastic” cells. The immunohistochemical profile was variable, including at least focal positivity for AE1-3 (10/10), cytokeratin 7 (7/10), epithelial membrane antigen (10/10), c-kit (6/10), antimitochondrial antigen (MIA;10/10), PAX-2 (9/10), AMACR (racemase;6/10), CD10 (5/10), parvalbumin (8/10), vimentin (6/10), claudin 7 (10/10), and claudin 8 (3/10). No immunoreactivity for carbonic anhydrase 9, HMB-45, S-100A1, and TFE3 was documented. We found no differences in the immunophenotype in the small cell oncocytes/oncoblasts that formed pseudorosettes and those that did not. However, there were differences in the immunohistochemical profile of classic oncocytes and small cell oncocytes/oncoblasts. Using array comparative genomic hybridization, no chromosomal changes were identified in any of the cases examined (n = 3). No numerical changes of chromosomes 7 and 17 were revealed on fluorescence in situ hybridization analysis (n = 3). In conclusion, we herein present the first study on small cell renal oncocytomas with formation of pseudorosettes. This is a rare subtype of oncocytoma, which may, especially on a core biopsy, present differential diagnostic difficulties. The immunohistochemical profile of these tumors is variable and differs in significant respects from that of conventional renal oncocytoma. Awareness of this entity and its immunohistochemical variability should help in distinguishing this rare tumor from malignant tumors with similar (small cell) histomorphologic features. All tumors behaved in a benign fashion during follow-up (mean, 3.1 years; median, 1 year).

Credits:

Petersson Fa,b, Síma Ra, Grossmann Pa, Michal Ma, Kuroda Nc, Hora Md, Yang Xe, Kinkor Za, Trivunic Sf, Zalud Rg, Sperga Mh, Jaunmuktane Zi, Branžovský Ja, Ferda Jj, Hes Oa.

  • a. Department of Pathology, Charles University and University Hospital, 301 60 Plzen, Czech Republic
  • b. Department of Pathology, National University Health System, 119 074 Singapore
  • c. Department of Pathology, Red Cross Hospital, 780-8262 Kochi, Japan
  • d. Department of Urology, Charles University Hospital, 305 99 Plzen, Czech Republic
  • e. Department of Pathology, Northwest University Chicaco, IL 60611, USA
  • f. Department of Pathology, University Novi Sad, 21000 Novi Sad, Serbia
  • g. Department of Pathology, Regional Hospital Kolin, 280 20 Kolin Czech Republic
  • h. Department of Pathology, Riga East University Hospital, LV-1038 Riga, Latvia
  • i. Department of Pathology, Stradini University Hospital, LV-1038 Riga, Latvia
  • j. Department of Radiology, Charles University and University Hospital, 304 60 Plzen, Czech Republic

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