What is your diagnosis? Perifemoral mass in a cow.
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.
Bisby
Tricia M
TM
Department of Comparative Pathobiology, Purdue University, West Lafayette, IN, USA. tbisby@purdue.edu
Pratt
Suzanne M
SM
Kent Fenton
R
R
Nickie Baird
A
A
Thompson
Craig A
CA
Lin
Tsang L
TL
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*