title: What is your diagnosis? Perifemoral mass in a cow.
abstract: A 15-year-old female Simmental cross-breed cow was presented to the Purdue University Veterinary Teaching Hospital for evaluation of a perifemoral soft tissue mass. Impression smears made from an excisional biopsy contained a population of pleomorphic mesenchymal cells with abundant, periodic acid-Schiff-positive (PAS), intracytoplasmic granular material, and rare elongated multinucleated cells consistent with strap-like cells. A second population of small round cells suggestive of lymphocytes or progenitor cells was also noted. A cytologic diagnosis of sarcoma was made, with rhabdomyosarcoma considered most likely based on the large amount of PAS-positive material (presumed to be glycogen) and the rare strap-like cells. Histopathologic sections contained an unencapsulated, densely cellular neoplasm composed of haphazardly arranged highly pleomorphic mesenchymal cells and a few small round cells. The mesenchymal cells were positive for vimentin, non-specific muscle actin, and myoglobin, and negative for phosphotungstic acid-hematoxylin, smooth muscle actin, and desmin. Glycogen granules were confirmed by transmission electron microscopy. A diagnosis of pleomorphic rhabdomyosarcoma was made. While cytologic findings may suggest rhabdomyosarcoma, cytologic features can be highly variable, and a definitive diagnosis usually requires cytochemical and immunohistochemical staining.
authors.affiliation: Department of Comparative Pathobiology, Purdue University, West Lafayette, IN, USA. tbisby@purdue.edu
authors.forename: Tricia M
authors.initials: TM
authors.lastname: Bisby
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Pratt
authors.forename: R
authors.initials: R
authors.lastname: Kent Fenton
authors.forename: A
authors.initials: A
authors.lastname: Nickie Baird
authors.forename: Craig A
authors.initials: CA
authors.lastname: Thompson
authors.forename: Tsang L
authors.initials: TL
authors.lastname: Lin
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis / Q000473:pathology*; D005260:Female; D006614:Hindlimb / Q000473:pathology; D019042:Muscle Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D011247:Pregnancy; D012208:Rhabdomyosarcoma / Q000473:pathology / Q000662:veterinary*