title: Diversity of Histologic Patterns and Expression of Cytoskeletal Proteins in Canine Skeletal Osteosarcoma.
abstract: Osteosarcoma (OS), the most common bone tumor, includes OS of the head (OSH) and appendicular OS (OSA). In dogs, it is classified into 6 histologic subtypes: osteoblastic, chondroblastic, fibroblastic, telangiectatic, giant cell, and poorly differentiated. This study investigated the significance of the histologic classification relevant to clinical outcome and the histologic and immunohistochemical relationships between pleomorphism and expression of cytoskeletal proteins in 60 cases each of OSH and OSA. Most neoplasms exhibited histologic diversity, and 64% of OS contained multiple subtypes. In addition to the above 6 subtypes, myxoid, round cell, and epithelioid subtypes were observed. Although the epithelioid subtypes were observed in only OSH, no significant difference in the frequency of other subtypes was observed. Also, no significant relevance was observed between the clinical outcome and histologic subtypes. Cytokeratin (CK) was expressed in both epithelioid and sarcomatoid tumor cells in various subtypes, and all CK-positive tumor cells also expressed vimentin. Vimentin and α-smooth muscle actin (SMA) were expressed in all subtypes. A few SMA-positive spindle-shaped tumor cells exhibited desmin expression. Glial fibrillary acidic protein-positive tumor cells were observed in many subtypes, and some of these cells showed neurofilament expression. Although OSH exhibited significantly stronger immunoreactivity for SMA than OSA, no significant difference in other cytoskeletal proteins was observed. Some tumor cells had cytoskeletal protein expression compatible with the corresponding histologic subtypes, such as CK in the epithelioid subtype and SMA in the fibroblastic subtype. Thus, canine skeletal OS is composed of pleomorphic and heterogenous tumor cells as is reflected in the diversity of histologic patterns and expression of cytoskeletal proteins.
authors.affiliation: Department of Veterinary Pathology, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Nagamine
authors.affiliation: Department of Veterinary Pathology, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hirayama
authors.affiliation: Department of Veterinary Pathology, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Matsuda
authors.affiliation: Department of Veterinary Pathology, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Okamoto
authors.affiliation: PATHO LABO, Ito, Shizuoka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ohmachi
authors.affiliation: Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kadosawa
authors.affiliation: Department of Veterinary Pathology, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan taniyama@rakuno.ac.jp.
authors.forename: H
authors.initials: H
authors.lastname: Taniyama
mesh_terms: D000818:Animals; D001859:Bone Neoplasms / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D001842:Bone and Bones / Q000378:metabolism / Q000473:pathology; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004283:Dog Diseases / Q000378:metabolism / Q000473:pathology*; D004285:Dogs; D005260:Female; D008297:Male; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*
chemical_list: D003598:Cytoskeletal Proteins
keywords: appendicular; canine; cytoskeleton; head; immunohistochemistry; osteosarcoma; pleomorphism