title: Of all the nerve! A subcutaneous forelimb mass on a cat.
abstract: A 16-year-old, male, neutered cat had a 2.5 X 1.5 cm mass on the medial aspect of the right carpus. Cytologic examination of a fine-needle aspirate of the mass indicated a markedly pleomorphic population of plasmacytoid to histiocytic-appearing cells. The cytologic diagnosis was malignant neoplasia of probable mesenchymal or round cell origin. The right forelimb was surgically removed and the scapular, axillary, and prescapular lymph nodes were excised. Malignant fibrous histiocytoma was tentatively diagnosed histologically; however, the tumor cells subsequently were found to be negative for histiocytic (MAC 387, antitrypsin), T-cell (CD3), and B-lymphocyte (immunoglobulin light chains, Ly 5/CD45R) markers, and positive for glial fibrillary acidic protein, vimentin, and S-100. Based on the immunohistochemical results, the diagnosis was modified to malignant peripheral nerve sheath tumor (PNST). Six months after surgery, the cat was reported to be well and had no evidence of metastasis. PNSTs are rare tumors in cats, and are considered as synonymous with schwannomas, neurofibrosarcomas, and hemangiopericytomas. In this cat, the plasmacytoid and pleomorphic appearance of the PNSTcells in cytologic and histologic specimens was unusual, and made it difficult to reach an accurate diagnosis without immunocytochemistry.
authors.affiliation: Hôpital Vétérinaire Duvernay, Laval, Québec, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Tremblay
authors.forename: Anne
authors.initials: A
authors.lastname: Lanevschi
authors.forename: Monique
authors.initials: M
authors.lastname: Doré
authors.forename: Isabelle
authors.initials: I
authors.lastname: Lanthier
authors.forename: Michel
authors.initials: M
authors.lastname: Desnoyers
mesh_terms: D000818:Animals; D044963:Biopsy, Fine-Needle / Q000379:methods / Q000662:veterinary; D002371:Cat Diseases / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D002415:Cats; D003937:Diagnosis, Differential; D005552:Forelimb; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D051677:Histiocytoma, Malignant Fibrous / Q000737:chemistry / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary; D007150:Immunohistochemistry / Q000379:methods / Q000662:veterinary; D007794:Lameness, Animal; D008297:Male; D018317:Nerve Sheath Neoplasms / Q000737:chemistry / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D009442:Neurilemmoma / Q000737:chemistry / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary; D009418:S100 Proteins / Q000032:analysis; D040521:Subcutaneous Tissue / Q000737:chemistry / Q000473:pathology*; D014746:Vimentin / Q000032:analysis
chemical_list: D005904:Glial Fibrillary Acidic Protein; D009418:S100 Proteins; D014746:Vimentin