Congenital cystic polypoid rectal hamartoma in a newborn foal

A neonatal foal with signs of rectal bleeding was diagnosed with an intraluminal rectal mass and intussusception on surgical exploration of the abdomen. Histologically, the mass consisted of cystic spaces lined by simple columnar epithelium with numerous goblet cells and was surrounded by thin bands of smooth muscle in a myxomatous stroma. Although the mass shared similarities with retrorectal cystic hamartoma (tailgut cyst) and juvenile polyps, described in human medicine, location and histologic findings were not entirely consistent with either condition.     

Mixed apocrine sweat gland tumor of the tail in a cow

A 4-year-old native-breed cow had a mass with wide areas of ulceration and hemorrhage at the base of the tail at the same level as the vulva. The tumor was 19 X 13 X 11 cm, appeared red-brown, and was firm to hard, with gritty areas apparent on cut surface. Histologically, the tumor mass was composed of multilayered epithelial cells forming glandular structures with occasional apical blebs and rare solidly packed cells in nests. The stroma included fibrous connective tissue, scattered or periglandular sheets of spindle-shaped cells resembling myoepithelium, several cartilaginous formations, and numerous irregular islands of mineralized osteoid, well-formed bone trabeculae lined by osteoblasts, and many osteoclast-like multinucleated giant cells among or near the neoplastic epithelium. Immunohistochemically, the neoplastic epithelium was positive for pan-cytokeratin (AE1/AE2) and cytokeratin 19 but was negative for cytokeratin 18. Spindle-shaped cells were stained with alpha smooth muscle actin (alphaSMA) and to a lesser extent vimentin antibodies. The cells of osteogenic lineage and spindle cells closely associated with the osteoid showed strong immunostaining for vimentin but not for alphaSMA. Immunostaining for neuron-specific enolase and S100 protein was not observed in any component of the tumor mass. These findings suggested that the origin of bone formation was undifferentiated mesenchymal cells with osteogenic potential.     

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.     

Use of multi‐detector computed tomographic angiography in the diagnosis of a parapharyngeal aneurysm in a 6‐week‐old foal

Multidetector‐row computed tomographic contrast angiography (MDCTA) is routinely employed to investigate vascular masses in human patients but, to date, the use of this technique to investigate an aneurysmal mass has not been reported in an equine case. The potential of MDCTA to investigate a right‐sided parapharyngeal mass in a 6‐week‐old Thoroughbred foal was therefore investigated. A 4‐slice helical computed tomography scanner was used on a superficial, firm, ovoid mass yielding arterial blood on fine needle aspiration. MDCTA enabled identification of the vessels involved thus assisting in forming a diagnosis based on the morphology of the lesion and aided surgical planning. Histology confirmed the presence of mural thrombus and calcification within the smooth muscle wall consistent with a true aneurysm. MDCTA provided additional information to conventional imaging in this case of vascular masses of the head and neck. The technique therefore has the potential to improve diagnosis and assist in the management of such lesions.     

An oral choristoma in a foal resembling hairy polyp in humans

A neonatal foal was presented with a 6.5-cm pedunculated mass arising from the upper deciduous incisors. The distal end was soft and covered by haired skin, whereas the proximal end was firm, covered with mucosal epithelium, and at the point of transection contained a fully developed tooth. Microscopically, the mass was covered by epidermis and mucosal epithelium and the remaining portion of the mass consisted of mature collagen, nonneoplastic fat and smooth muscle, and a single tooth within a bony socket. The mass is consistent with an oral choristoma and has features similar to those described for hairy polyp in humans.     

Three cases of canine gastrointestinal stromal tumors with multiple differentiations and c-kit-expression

Three canine gastrointestinal stromal tumors (GISTs) were examined. Histopathologically, the tumor mass in the jejunum (Case 1) consisted of the proliferation of epithelioid cells with abundant eosinophilic or vacuolated cytoplasm. Gangliocyte-like or multinucleated giant cells were scattered. The tumor cells exhibited neural natures mimicking human gastrointestinal autonomic nerve tumors, which were immunopositive for several neuronal markers. Another jejunal mass (Case 2) was composed by a solid proliferation of spindle-shaped cells, arranging in interlacing fascicles and occasional storiform pattern. The tumor seemed to be classified undifferentiated GISTs, that showed no apparent neural or muscular features by ultrastructural and immunohistochemical examinations. In the pyloric mass (Case 3), the spindle cells having eosinophilic processes and elongated nuclei were arranged in sheets. Immunohistochemically, the tumor cells showed muscular natures as regards alpha smooth muscle actin and desmin expression.     

Vaccine-associated rhabdomyosarcoma with spinal epidural invasion and pulmonary metastasis in a cat

A 7-year-old, female, domestic medium-haired cat had a recurrent deep dermal mass in the interscapular region after initial surgical removal 3 months earlier. The cat had received a killed rabies vaccine and a five-in-one vaccine in the same area about 2 months prior to the first surgery. The relapsed mass was diagnosed as vaccine-associated sarcoma. The cat was euthanized 2 months later because of hind limb paralysis. At necropsy, multiple, poorly demarcated, nodular masses were seen in the muscles around the shoulders, neck, and thoracic vertebrae. Pulmonary metastasis and spinal epidural invasion at T1-T3 with regional cord compression and malacia were observed. Microscopically, the masses consisted of interwoven bundles of spindle cells with prominent multinucleated giant cell formation. The neoplastic cells stained strongly positive for myoglobin, and moderately but variably positive for vimentin, desmin, and alpha- smooth muscle actin. Phosphotungstic acid-hematoxylin staining revealed cytoplasmic striations in scattered tumor cells. The tumor was considered a vaccine-associated rhabdomyosarcoma.     

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.     

Hemothorax associated with telangiectatic osteosarcoma in a dog

Hemothorax in a dog was attributed to bleeding from an intrathoracic mass attached to the sixth through the tenth ribs. The mass contained numerous cavernous, blood-filled spaces as well as bands of osteoid and occasional foci of osseous tissue. The diagnosis was telangiectatic osteosarcoma. Telangiectatic osteosarcoma is an uncommon variant of osteosarcoma. Cavernous, blood-filled spaces and paucity of bone are important histologic features. Metastasis was described in one of the seven telangiectatic osteosarcomas reported in dogs, and none was found in this case.     

Multilobular tumor of the mandible in a Pekingese dog

Multilobular tumor of bone detected in a 2.5-year-old male Pekingese dog is reported. Grossly, the neoplasm consisted of multiple, variably sized, gritty, grayish-white to yellow nodules separated by thick collagenous septa. Histologically, these nodules contained multiple lobules of irregularly shaped and sized islands of well-differentiated osteoid and cartilage, separated by anastomosing fibrovascular septa. Chondrocytes and osteocytes were observed in the lacunae and in more osseous islands in the lobule, respectively. These lobules were surrounded by mesenchymal spindle cells. Mitotic figures were not evident. The neoplastic pattern was consistent with that of a multilobular bone tumor. Diagnosis was based on gross and light microscopic findings. The cause of this neoplasm was not determined.     

Multiple aneurysmal bone cysts in a foal.

Multiple aneurysmal bone cysts (ABCs) are previously unreported in horses. An ABC was diagnosed in the left 3rd metacarpal of a Thoroughbred foal, which partially resolved following surgical curettage. A 2nd ABC developed in the left tibia, 7 wk postoperatively, and the foal was euthanized.     

Primary ureteral giant cell sarcoma in a Pomeranian

An 8-year-old male neutered Pomeranian dog was presented to the Veterinary Teaching Hospital at Oregon State University for surgical treatment of hydronephrosis of the left kidney and a left cranial abdominal mass. A primary ureteral mass was found during exploratory surgery, and the mass was resected and ureteral anastomosis was performed. Cytologic evaluation of the mass revealed 3 distinct cell populations, including a large number of multinucleated giant cells, a moderate number of thin spindle-shaped cells, and cohesive clusters of transitional epithelial cells. The cytologic diagnosis was giant cell sarcoma. The diagnosis was confirmed by histologic examination, and immunohistochemical staining was performed. The spindle-shaped cells and multinucleated giant cells were both immunoreactive for vimentin and spindle-shaped cells for S-100. Tumor cells did not express wide-spectrum cytokeratin, broad-spectrum muscle actin, smooth muscle actin, sarcomeric actin, desmin, BLA36, Mac 387, synaptophysin, neuron-specific enolase, glial fibrillary acid protein, or von Willebrand factor. These findings are most consistent with an anaplastic sarcoma with giant cells. This is the first case report of a primary ureteral giant cell sarcoma in a dog.     

A mixed apocrine gland tumor with metastases to the bone and bone marrow in a miniature poodle

A 10-year-old female miniature poodle had a mass in its carpal joint of the left forelimb. The tumor was divided into small multiple lobules by delicate connective tissues, and necroses were found in some of the central lobules. In some connective stromal areas, chondroid and osteoid tissues were formed. The tumor cells were similar to the structure of apocrine gland epithelial cells with apical blebs resembling apocrine secretion and eosinophilic secretary materials within the luminal space, and spindle cells were sometimes found in the basal area of the glandular structure. In some areas, tumor cells invaded in the blood vessels, bone and bone marrow. Immunohistochemically, the tumor cells forming tubulo-acinar to solid structures were intensely positive for cytokeratin and keratin K8/K18, and the spindle cells were positive for vimentin and alpha-smooth muscle actin. This case was diagnosed as a malignant mixed apocrine gland tumor with metastases to the bone and bone marrow.     

Corneal invasion by hemangiosarcoma in a horse

A 15-year-old gray Arabian gelding presented for evaluation of a lateral limbal mass extending across approximately 30% of the cornea. Grossly, the raised mass appeared nonpigmented, smooth, and irregular in shape, with an area of central necrosis and serosanguinous discharge. The mass was removed via lamellar keratectomy and histopathologic evaluation revealed features characteristic of hemangiosarcoma (HSA), including irregular vascular channels lined by a plump spindle cell population. Immunohistochemistry results showed that the neoplastic cells lining the vascular channels present diffuse and strong cytoplasmic reaction with von Willebrand Factor and the perivascular spindle cells exhibit moderate cytoplasmic reaction for smooth muscle actin. A lack of cytokeratin staining definitively excluded a diagnosis of atypical squamous cell carcinoma. Smooth muscle actin staining of the perivascular cells adjacent to the neoplastic endothelial cells is not a feature commonly described in HSA and has not been reported in previous cases of equine HSA. The horse remained in good health 21 months postkeratectomy and has exceeded the survival time of previously documented equine ocular HSA cases where more extreme surgical excision was performed.     

Feline cystic thymoma: a clinicopathologic,immunohistologic, and electron microscopic study of 14 cases

Cystic thymoma was diagnosed in 14 cats in a period of 6 years. The most common clinical sign was laboured breathing. The tumours were characterized by various-sized cystic spaces with central vessels. The epithelial cells varied from oval to spindle to polygonal cells enclosing cystic spaces or in pure epithelial cell components. The nuclei of the neoplastic cells had scattered chromatin and small nucleoli. The cytoplasm was pale eosinophilic. The concentration of mature lymphocytes varied from area to area with rare germinal centres. Immunohistochemically, the epithelial cells stained only with AE(1)/AE(3). The central vessels were positive for vimentin, smooth muscle actin, and factor VIII antigen. Electron microscopy revealed that the cyst walls were lined by epithelial cells that were joined by desmosomes, and the walls were well separated from the cystic spaces by a well-defined basement membrane. The neoplastic epithelial cells contained scattered tonofilaments. Three of the cats had metastasis to the lymph nodes and lungs. Two novel cases of ectopic cystic thymoma have also been described. Results of this study reveal that cystic thymoma is uncommon in cats, and that the histomorphologic, immunohistochemical, and electron microscopic features are similar to those of cystic thymoma in humans.     

Primary subcutaneous leiomyosarcoma of the hamster hind leg

We report the first case of a primary subcutaneous leiomyosarcoma that originated in the hind leg of a hamster and metastasized to the bone marrow, lung and diaphragm. A 10-month-old female Syrian golden hamster was presented with a large, firm, white subcutaneous mass in the right hind leg. The tumor invaded into the bone marrow and small nodules were also present in the lung and diaphragm; however, no tumor masses were found in the visceral organs. Histologically, the tumors were spindle cell sarcomas, composed of densely packed pleomorphic spindle cells with oval to elongate nuclei and moderate amounts of eosinophilic cytoplasm. Immunohistochemically, the neoplastic cells were positive for vimentin, desmin, and smooth muscle actin, but negative for alpha-sarcomeric actin and S-100. Thus, the diagnosis was primary leiomyosarcoma of the hind leg with metastasis to the bone marrow, lung and diaphragm. To the best of our knowledge, this is the first report of spontaneous primary subcutaneous leiomyosarcoma of the hind leg with distant metastasis in laboratory animals.     

Rhabdomyosarcoma associated with the lead wire of a pacemaker generator implant

An 11‐year‐old female spayed Labrador Retriever was presented for a draining, painful subcutaneous mass palpated over a previously implanted pacemaker generator. Infection was suspected and the mass was removed surgically. On cut surface, the mass was friable and mottled tan to brown with firm pale tan nodules, surrounding the pacemaker lead wire adjacent to the pacemaker generator. Cytologic interpretation of impression smears was consistent with a sarcoma, and suggestive of a rhabdomyosarcoma due to the presence of strap‐like cells. On histopathologic examination, a highly invasive nodular mass surrounded the pacemaker lead, composed of pleomorphic round, spindle and strap cells, and multinucleated giant cells. The population exhibited microscopic invasion into the deep portion of the fibrous capsule surrounding the pacemaker generator. There were tumor emboli within small to medium subcutaneous veins adjacent to the mass. Immunohistochemically, the neoplastic cells stained positive for α‐sarcomeric actin and vimentin, and negative for α‐smooth muscle actin, consistent with a rhabdomyosarcoma arising at the site of the pacemaker generator. To our knowledge, this is the first report of a rhabdomyosarcoma associated with the lead wire of a pacemaker generator in a dog.     

Cytologic findings from a benign giant cell tumor of the tendon sheath in a dog

A 6‐year‐old male neutered Australian Shepherd dog was presented for evaluation of a subcutaneous mass on the plantar aspect of the proximal left metatarsus. Fine‐needle aspirate smears contained numerous plump spindle cells and large multinucleated cells amongst a considerable amount of pink extracellular matrix. Histopathologic diagnosis of the tissue obtained during initial biopsy and eventual surgical cytoreduction of the mass was a benign giant cell tumor of the tendon sheath (GCTTS). Immunohistochemically, the synovioblastic neoplastic cells were diffusely strongly positive for vimentin and S‐100, were multifocally moderately positive for cytokeratin AE1/3, and were negative for CD18, muscle‐specific actin (MSA), and melanoma‐associated antigen (mutated) 1 (MUM‐1). The dog recovered from surgery and underwent definitive radiation therapy to treat the local residual disease. Eight months later, the mass had not recurred. The diagnosis of GCTTS in this case supports previously published reports describing GCTTS as a relevant disease entity in dogs, and provides the first documentation of cytologic findings with this tumor. Further investigation is needed to correlate pathologic features with clinical behavior and response to therapy in dogs.     

Surgical treatment of a large congenital cavernous haemangioma on the thorax of a foal

A 3‐day‐old male foal was presented with a fluctuant 25 × 15 cm mass on the thorax. The mass had increased in size since birth. The mass did not respond to conservative treatment consisting of aspiration of serohaemorrhagic contents and compression bandages, and it was therefore surgically removed when the foal was approximately 2½ weeks. A histopathological diagnosis of cavernous haemangioma was made. Healing progressed without complications despite a large surgical wound left to heal by second intention. Recurrence was not observed during the 1.5‐year follow‐up period.     

Xanthogranulomatous inflammation of the small bowel in a dog

A case of xanthogranulomatous inflammation of the small bowel in a 12-year-old male American Staffordshire Terrier is described. Disseminated yellow-white nodules 2 to 3 mm in diameter bulging on the serosal surface of the small bowel, as well as on mesenteric tissue, were detected. Histopathologic examination revealed a nodular collection of foamy cells, mainly involving serosal and muscular layers, associated with necrotic areas, hemorrhages, neovascularization, variable numbers of reactive spindle cells, neutrophils, lymphocytes, plasma cells, and rare multinucleated giant cells. Transmural lymphangectasia and mucosal lymphoplasmacytic inflammation were also observed. Both Oil Red O stain and ultrastructural study revealed lipid droplets in the cytoplasm of foamy cells. Lysozyme immunoreactivity was detected in single as well as in clustered foamy cells, while smooth muscle actin was positive in spindle cells and scattered foamy elements. Lymphangectasia associated with lymphoplasmacytic enteritis suggests a component of lymphatic fluid stasis in the pathogenesis of such lesions.