Intestinal leiomyosarcoma in a cat

Intramural ileocaecocolic leiomyosarcoma is described in an elderly neutered male domestic shorthaired cat with poor appetite and weight loss. Histological examination of the resected lesion revealed a poorly differentiated soft tissue sarcoma and a diagnosis of leiomyosarcoma was confirmed by positive immunohistochemical staining for vimentin and a-smooth muscle actin. Postoperative survival time was 102 days before local recurrence justified euthanasia.     

Dermal intravascular leiomyosarcoma in a cat

A 10-year-old female spayed domestic shorthaired cat presented with a subcutaneous tumor between the first and second phalanges of the left hind foot. Six months after excision, a similar tumor occurred on the medial aspect of the third phalanx of the same limb. Histologically, both tumors consisted of solid masses of spindle and round cells, many of which grew within endothelial-lined vessels. Tumor cells stained positively for smooth muscle actin and vimentin, but were negative for cytokeratin, S-100, desmin, synaptophysin, factor VIII-related antigen, and neuron-specific enolase. The diagnosis was dermal intravascular leiomyosarcoma.     

Ocular myxoid leiomyosarcoma in a cat

A case of myxoid leiomyosarcoma likely of iris dilator muscle origin in the enucleated eye of a 6-year-old domestic short haired cat is reported. The poorly demarcated mass expanded the iris, partially filled the globe and extended into the optic nerve. The mass was composed of spindle cells separated by abundant matrix positive for mucopolysaccharides with alcian blue. The neoplastic cells were immunoreactive for smooth muscle actin (SMA), S100 and vimentin, and negative for cytokeratin, Melan-A, glial fibrillary protein (GFAP) and desmin. There was no evidence of recurrence or metastasis 6 months after enucleation.     

Uterine myxoid leiomyosarcoma with widespread metastases in a cat

A 10-year-old domestic shorthair cat was spayed to remove bilateral ovarian masses and an enlarged uterus. Both ovaries were effaced by large, irregular, firm, glistening, white cystic masses filled with clear viscous fluid. The uterine lumen was filled with copious amounts of clear viscous fluid, and the uterus contained multiple, firm, glistening, white nodules. Histologic examination revealed an invasive spindle cell neoplasm with features of malignancy, and extensive hypocellular areas containing an alcian blue-positive myxoid matrix. Tumor cells expressed caldesmon, alpha-smooth muscle actin, and estrogen receptor but were negative for desmin. The animal was euthanized 1 month later because of suspected local tumor recurrence. At necropsy, the abdominal cavity contained 120 ml of mucoid ascites; multiple tumor nodules were present in the abdominal and thoracic cavities. The clinical behavior and gross, microscopic, and immunohistochemical findings established a diagnosis of myxoid leiomyosarcoma.     

Vulvar lipoleiomyoma in a dog.

A vulvar neoplasm from a 5-year-old female Siberian Husky dog was removed surgically and examined histologically. Macroscopically, the neoplasm was firm, white, and measured 6 x 4 x 3 cm. Microscopically, the neoplasm was expansile, nonencapsulated, and composed of lobules of mature adipocytes ad-mixed with streams and bundles of well-differentiated smooth muscle cells. Immunohistochemically, the neoplastic cells had strong diffuse cytoplasmic immunoreactivity for alpha-smooth muscle actin and desmin, and no immunoreactivity for cytokeratin or vimentin. On the basis of gross, histopathologic, and immunohistochemical findings, a diagnosis of lipoleiomyoma was made. This is, to the author's knowledge, the first report of canine vulvar lipoleiomyoma.     

Vestibulovaginal leiomyosarcoma in a mare

A 14-year-old Quarter Horse mare presented for a mass within the vestibule and vagina resulting in external compression and incomplete occlusion at the external urethral opening with subsequent difficulty urinating. Examination revealed an approximately 15 × 10 cm lobulated mass within the vestibule and caudal vagina attached via a broad base dorsally. Histopathology of the mass identified a low-grade leiomyosarcoma. Complete resection was not possible, and surgical debulking of the mass was performed during standing sedation using a vessel-sealing and dividing device. The mare was discharged 3 days post-operatively without any complications. Recheck examinations performed at 1 month and 8 months’ post-surgery revealed excellent healing of the surgical site and no apparent tumour regrowth.     

Rectal leiomyosarcoma in a horse

A mass originating from the dorsal rectal wall of a 4-year-old mare was diagnosed as a leiomyosarcoma. General anesthesia and meticulous surgical dissection were required to effect removal. In spite of incomplete excision, as indicated by histologic sections, the mass has not recurred in the 18 months since removal.     

Multicentric leiomyosarcoma in a young male horse

A 2-year-old male Thoroughbred was evaluated for multiple firm, raised nodules of the maxilla and mandible that had been present since 6 months of age. The horse was evaluated as a yearling with a final histologic diagnosis of fibrosarcoma. As a 2-year-old, the colt made a loud upper airway sound and was agitated after strenuous exercise. Results of upper airway endoscopy indicated severe narrowing of the nasal passages and pharynx with normal resting function. Radiography revealed multiple circular bony lesions in the mandible, maxilla, multiple long bones, and cervical vertebrae. Biopsy specimens of the left mandible and right facial bone were obtained. A diagnosis of leiomyosarcoma with extensive metastatic bone formation was made on the basis of histologic features and the immunohistochemical staining properties of the biopsy specimens. Because of the diffuse distribution of the lesions, prognosis was guarded; 4 years after diagnosis, the horse had not pursued an athletic career.     

Gastric pleomorphic leiomyosarcoma in a Shetland sheepdog

A solitary mass of 6 x 6 x 5 cm was found in the smooth muscle layer of the pyloric part in the stomach of a Shetland sheepdog. The excised mass was solid, gray-white in color, and had central necrosis with hemorrhages. Microscopically, the neoplasm was composed of irregular bundles of spindle-shaped tumor cells and round tumor cells. A few multinucleated cells and gangliocyte-like cells were observed. The nuclei exhibited a high degree of atypia and many cells contained mitotic figures. Immunohistochemically, tumor cells were positive for vimentin and desmin, but negative for c-kit antibody. Ultrastructurally, tumor cells contained cytoplasmic myofilaments and pinocytotic vesicles. Based on these pathological findings, the tumor was diagnosed as gastric pleomorphic leiomyosarcoma.     

Uterine leiomyosarcoma and pyometra in a dog

A seven-year-old entire female, mixed-breed dog, weighing 19 kg, was presented with a 2-day history of abdominal distension, reduced appetite and general dullness. Abdominal palpation revealed a large mass. Radiography showed a large mass occupying the left mid-abdominal area and convoluted loops of tubular fluid opacity occupying the right mid-abdominal area. Ultrasonography revealed a large heterogeneous mass with an anechoic area and some hyperechoic foci, indicative of calcification, in the mid-abdominal area. Furthermore, hypoechoic areas were found in the middle and caudal abdominal area and were presumed to be the fluid-filled uterine horns. At laparotomy, a 10·5×14·5-cm firm mass was found in the uterine body, while the uterine horns were filled with a thick red-brownish exudate; ovariohysterectomy was subsequently performed. A diagnosis of uterine leiomyosarcoma associated with pyometra was established by histopathology and immunohistochemistry.