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.

Pathology in Practice

“…Immunohistochemical analysis is necessary for a definitive diagnosis because features such as nonuniform texture and color of surfaces, marked cellular pleomorphism, high mitotic index, and local invasion of surrounding tissues are not specific to this soft tissue tumor. Previous reports 4,[7][8][9][10][11][12][13][14][15][16][17][18][19] of rhabdomyosarcomas in horses and cattle consistently used MyoD1 or myogenin labeling for confirmation of muscle differentiation and myoglobin and MyoD1 for confirmation of striated muscle differentiation, as was done in this case.…”

“…4,[15][16][17][18][19] Rhabdomyosarcomas have been identified in the abdominal wall, 14 tongue, 10,14 shoulder region, 9,14 masseter muscle, 14 buccal muscles, 14 heart, 14 urinary bladder, 11 uterus, 12 hind limbs, 8 and deep digital flexor tendon 13 in horses. In cattle, rhabdomyosarcomas involving the abdominal wall, 15 brisket, 16 pleura, 4 thoracic wall, 18 perifemoral soft tissue, 17 and heart 19 have been reported. The location of the mass between the thorax and scapula in the case described in this report is therefore not particularly unusual.…”

Primary pharyngeal alveolar rhabdomyosarcoma in an adolescent Japanese black heifer

“…[ 1 ] Pleomorphic Crossbred 15 y Skeletal muscle around the femur Bisby et al . [ 3 ] ND: Not descripted, y: year, m: month, LN: lymph node. ), only one bovine ARMS case has been published [ 17 ].…”

“…Moreover, among the eight bovine RMS cases, only one occurred in the head, but not the oropharynx, regardless of category [ 25 ]. The most common sites for bovine cases include the body cavity and body cavity organs without skeletal muscle [ 13 , 14 , 15 , 17 ], although two cases of skeletal muscle origin and one case of myocardial origin have been reported [ 1 , 3 , 24 ]. Thus, the current case can be considered rare among cows in terms of the involved site and RMS subtype but share identical characteristics with human and canine cases.…”