Urethral stromal tumor with pacemaker cell phenotype

William A. Kanner, Cinthia B. Drachenberg, John C. Papadimitriou, Suna Wang, Stephen J. Meltzer, Geoffrey N. Sklar

Research output: Contribution to journalArticlepeer-review


Penile malignancies are rare in developed countries. The authors present a case of a penile urethral mesenchymal tumor occurring in a 51-year-old Caucasian male and displaying light microscopic, immunohistochemical, and ultrastructural features suggestive of a pacemaker cell type, combined with a lack of diagnostic features of any other established tumor category. The immunohistochemical profile was intensely positive for vimentin, PKC θ, and NSE and weakly positive to nonreactive for CD34 and smooth muscle actin, and entirely negative for CD117 (c-kit), S-100, and other markers. C-kit and PDGFRA gene analysis showed no mutations. Electron microscopy revealed tumor cells with plentiful cytoplasm and cytoplasmic processes/filopodia, both filled with intermediate filaments and occasional solitary focal densities. There were also prominent smooth endoplasmic reticulum cisternae, caveolae, neurosecretory granules, particularly concentrated in cytoplasmic processes, and synaptic-type structures. Poorly formed basal lamina, gap junctions, and intercellular collagen aggregates, consistent with skeinoid-type fibers, were also noted. Interstitial cells with potential pacemaker function have been recently described in the lower urinary tract, including the urethra, and this tumor may be related to this cellular phenotype.

Original languageEnglish (US)
Pages (from-to)63-71
Number of pages9
JournalUltrastructural Pathology
Issue number1
StatePublished - Feb 2007
Externally publishedYes


  • Cajal cells
  • GIST
  • Interstitial cells
  • Penis
  • Sarcoma
  • c-kit

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Structural Biology


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