Disseminated Pleomorphic Myofibrosarcoma in a Grizzly Bear (Ursus arctos horribilis)

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3 Scopus citations


The pathological and diagnostic features of a widely disseminated pleomorphic high-grade myofibroblastic sarcoma are described in a 23-year-old male brown bear (Ursus arctos horribilis). Firm, solid, white to tan neoplastic nodules, often with cavitated or soft grey-red necrotic centres, were observed throughout most internal organs, subcutaneous tissues and skeletal muscles on gross examination. Microscopically, the tumour consisted of pleomorphic spindle cells forming interlacing fascicles with a focal storiform pattern with large numbers of bizarre polygonal multinucleate cells, frequently within a collagenous stroma. Immunohistochemistry, Masson's trichrome stain and transmission electron microscopy designated the myofibroblast as the cell of origin. This is the first case of a high-grade myofibrosarcoma in a grizzly bear.

Original languageEnglish (US)
Pages (from-to)376-380
Number of pages5
JournalJournal of Comparative Pathology
Issue number2-3
StatePublished - Aug 2012


  • Electron microscopy
  • Grizzly bear
  • Immunohistochemistry
  • Myofibrosarcoma

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • veterinary(all)


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