Renal cell tumors with an entrapped papillary component: a collision with predilection for oncocytic tumors

Sean R. Williamson, Liang Cheng, Ramya Gadde, Giovanna A. Giannico, Matthew J. Wasco, Paul J. Taylor Smith, Nilesh S. Gupta, David J. Grignon, Merce Jorda, Oleksandr N. Kryvenko

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Renal cell tumors with mixed morphology resembling multiple renal cell carcinoma (RCC) subtypes are generally regarded as unclassified RCC. However, occasionally, papillary adenoma or RCC appears admixed with a larger, different tumor histology. We retrieved 17 renal tumors containing a papillary adenoma or papillary RCC component admixed with another tumor histology and studied them with immunohistochemistry and fluorescence in situ hybridization (FISH). Larger tumors were oncocytomas (n = 10), chromophobe RCCs (n = 5), borderline oncocytic tumor (n = 1), and clear cell RCC (n = 1). The size of papillary component ranged from 1 to 34 mm. One tumor was an oncocytoma encircled by a cyst (2.0 cm) with papillary hyperplasia of the lining. The papillary lesions were diffusely cytokeratin 7 positive (17/17), in contrast to “host” tumors. Alpha-methylacyl-coA-racemase labeling was usually stronger in the papillary lesions (13/15). KIT was negative in all papillary lesions and the clear cell RCC and positive in 16/16 oncocytic or chromophobe tumors. Eight of 15 (53%) collision tumors had differing FISH results in the two components. A papillary renal cell proliferation within another tumor is an uncommon phenomenon with predilection for oncocytoma and chromophobe RCC, possibly related to their common entrapment of benign tubules. When supported by distinct morphology and immunohistochemistry in these two components, this phenomenon should be diagnosed as a collision of two processes. A diagnosis of unclassified RCC should be avoided, due to potential misrepresentation as an aggressive renal cancer.

Original languageEnglish (US)
Pages (from-to)399-407
Number of pages9
JournalVirchows Archiv
Issue number3
StatePublished - Mar 1 2020


  • Collision tumor
  • Oncocytoma
  • Papillary adenoma
  • Renal cell carcinoma

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Molecular Biology
  • Cell Biology


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