Differentiated embryonal rhabdomyosarcoma in a cow

Rhabdomyosarcoma of the tongue in a neonatal calf

A newborn male Holstein calf developed a nodular enlargement at the tip of the tongue. Histopathological examination of the mass revealed predominant proliferating small, round, spindloid or polygonal neoplastic cells with scattered myoblast- and myotube-like cells and multinuclear giant cells. Phosphotungstic acid haematoxylin staining revealed cytoplasmic cross-striations in a few neoplastic cells. Neoplastic cells were immunopositive for vimentin, desmin, myoD1, myogenin, myoglobin and α-smooth muscle actin. The mass was diagnosed as embryonal rhabdomyosarcoma. To the best of our knowledge, this is the first reported case of bovine congenital lingual rhabdomyosarcoma, which is rare in animals.

Primary pharyngeal alveolar rhabdomyosarcoma in an adolescent Japanese black heifer

Alveolar rhabdomyosarcoma (ARMS) is a rare mesenchymal tumor with differentiation toward the skeletal muscle. Although several cases of canine ARMS have been reported in veterinary medicine, only one case of abdominal ARMS has been reported in a cow. A 13-month-old, Japanese black heifer was referred for pus-like nasal discharge. On autopsy, an 11 × 7 × 4.5-cm pedunculated mass closed to the left palatine tonsillar sinus that occupied the laryngopharynx. Histopathological and immunohistochemical analyses indicated that the tumor was a typical ARMS. To the best of our knowledge, this has been the first case of primary pharyngeal ARMS in a Japanese black heifer, which is rare among cows. Nonetheless, its characteristics, including site, age and subtype, are identical to those among humans and dogs.

Rhabdomyosarcoma with posterior paresis and megaesophagus in a Holstein heifer

A 7-month-old Holstein heifer presented with posterior paresis and megaesophagus. At post mortem examination, a nodular tumor was found attached to the thoracic wall and the eighth to eleventh thoracic vertebrae, adjacent to the left posterior pulmonary lobe. The tumor was diagnosed as rhabdomyosarcoma by histology. This is a very rare case of spinal infiltration of rhabdomyosarcoma in cattle.

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.

Embryonal Rhabdomyosarcoma in a Young Maine Coon Cat

Embryonal rhabdomyosarcomas are uncommon tumors in all domestic species, especially cats. A 14-month-old Maine coon was diagnosed with an embryonal rhabdomyosarcoma in the rectus abdominus muscle, which was treated with complete surgical excision. Although no clinical progression was noted after surgery, the cat succumbed to pulmonary metastasis within 7 months. The histological diagnosis was embryonal rhabdomyosarcoma (myotubular subtype). This category of striated muscle tumors is thought to have a more aggressive clinical course. The rapid demise of this cat even with no clinical or histological evidence of metastasis at the time of resection may indicate that, as in human medicine, adjuvant chemotherapy should be considered in conjunction with early surgical excision in preventing disease progression.

What is your diagnosis? Lingual mass in a dog

A 3.5-year-old female spayed Rat Terrier was presented for evaluation of a submucosal lingual mass. Fine-needle aspiration of the mass revealed a population of neoplastic cells composed predominantly of small, round cells and large, round to spindle-shaped cells, which occasionally had blunt cytoplasmic borders and multiple nuclei. The neoplastic cells had moderate to marked anisocytosis and anisokaryosis. The cytologic interpretation was malignant neoplasia, most likely sarcoma. Histopathologic examination of a biopsy specimen revealed an unencapsulated, poorly demarcated, moderately cellular neoplasm composed of individualized, infiltrative spindle cells. Elongate skeletal muscle cells with prominent, rectangular borders (strap cells) were observed. A morphologic diagnosis of rhabdomyosarcoma was made. Staining with phosphotungstic acid-hematoxylin revealed haphazardly arranged skeletal muscle cross-striations. Immunohistochemical staining results for vimentin, Myo D1, desmin, and myoglobin were positive, though staining intensity of tumor cells varied with the degree of differentiation. Using transmission electron microscopy, irregular, disorganized Z-bands were identified. Rhabdomyosarcomas are uncommon tumors in the dog, and rarely may involve the tongue or oral cavity. Cytologic evaluation of a rhabdomyosarcoma may reveal a pleomorphic population of cells and definitive diagnosis may require histologic examination, immunohistochemical staining, and electron microscopy.

Pleomorphic rhabdomyosarcoma in a cow

In a 5-year-old Holstein cow, a neoplasm composed of a large intramuscular mass and multiple metastases in the lungs and lymph nodes was diagnosed as a pleomorphic rhabdomyosarcoma. This neoplasm was characterized by marked variation in tumor cell size and giant cells with single bizarre nuclei. Although the presence of cross striations and myoglobin could be confirmed, expression of alpha-smooth muscle actin (SMA) was also recognized in a few cells. Neoplastic cells showing intense staining for desmin, vimentin and proliferating cell nuclear antigen irrespective of their size differed from those in an embryonal rhabdomyosarcoma that exhibited a wide spectrum of differentiation, reminiscent of normal skeletal myogenesis. The cellular pleomorphism and SMA expression seemed to be characteristic of deviation from normal muscle cells or satellite cells in adult muscle.