title: Orbital extraskeletal osteosarcoma following enucleation in a cat: a case report.
abstract: OBJECTIVE
  We present a unique case of a feline orbital extraskeletal osteosarcoma that developed 5 years post-enucleation.
  
  
  METHODS
  In 2002, an ophthalmologist enucleated the left eye of a 2-year-old neutered male DSH and submitted it to the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW). COPLOW diagnosed the left eye with feline diffuse iris melanoma. In June 2007, the cat presented to another veterinarian for moderate swelling of the enucleation site. Palpation suggested a firm mass along the lateral orbital rim and an exploratory orbitotomy revealed a cyst with a mass adhered to it and the ventrolateral orbital rim. The cyst and mass were excised by the veterinarian and submitted to COPLOW. COPLOW diagnosed the tissue as an orbital conjunctival inclusion cyst and an acquired orbital osteosarcoma.
  
  
  CONCLUSIONS
  Following the enucleation, retained conjunctival epithelium became embedded in the connective tissue of the orbit and caused a cyst to develop. The cyst wall consisted of a myofibroblastic collagen-rich matrix and acted as a nidus of chronic irritation and tumor growth. This orbital osteosarcoma resembles feline vaccine-associated sarcomas (VAS), feline post-traumatic ocular sarcomas, and microchip-associated sarcomas in terms of it histopathology and its hypothesized pathogenesis related to exposure to antigenic material such as implanted epithelium, lens protein, vaccine components, and microchips as foreign bodies.
authors.affiliation: Department of Pathobiological Sciences, School of Veterinary Medicine, Comparative Ocular Pathology Laboratory of Wisconsin, University of Wisconsin-Madison, 2015 Linden Drive, Madison, Wisconsin 53706-1102, USA. bsgrosko@wisc.edu
authors.forename: Brooke S
authors.initials: BS
authors.lastname: Groskopf
authors.forename: Richard R
authors.initials: RR
authors.lastname: Dubielzig
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Beaumont
mesh_terms: D000818:Animals; D002371:Cat Diseases / Q000473:pathology*; D002415:Cats; D003560:Cysts / Q000473:pathology / Q000662:veterinary; D015353:Eye Enucleation / Q000009:adverse effects / Q000662:veterinary*; D008297:Male; D008545:Melanoma / Q000601:surgery / Q000662:veterinary; D009916:Orbital Diseases / Q000209:etiology / Q000601:surgery / Q000662:veterinary*; D012516:Osteosarcoma / Q000473:pathology / Q000662:veterinary*; D011183:Postoperative Complications / Q000473:pathology / Q000662:veterinary*