Glomus tumours in the skin and subcutis of three horses

Three horses presented with variably painful, nonulcerated masses of the head or neck that were diagnosed as glomus tumours. Grossly, they were fleshy, pink to tan masses ranging from 0.4 to 9 cm in diameter, involving either the deep dermis and subcutis or the subcutis and underlying skeletal muscle. Microscopically, neoplastic epithelioid cells were arranged in sheets, cords and packets within lobules. The neoplastic cells frequently abutted and formed nodular bulges into large endothelium-lined vascular spaces, especially around the tumour periphery. Large nerve branches were associated with each tumour. As determined by immunohistochemistry, the neoplastic cells consistently expressed α-smooth muscle actin and vimentin, and some cells in two of the cases expressed desmin. A laminin- or collagen IV-positive basement membrane was demonstrated around individual tumour cells or small groups of cells in all three cases. Morphological features and immunohistochemistry supported the diagnosis of glomus tumour, most consistent with the solid type in humans. Applying a classification system used in humans, two of these tumours met criteria of malignancy (glomangiosarcomas). One horse was euthanized due to complications associated with recurrence and treatment-related necrosis and secondary infection.     

Pathological changes caused by Anoplocephala perfoliata in the mucosa/submucosa and in the enteric nervous system of equine ileocecal junction

In this study, pathological changes caused by Anoplocephala perfoliata in the ileocecal junction were investigated in 31 regularly slaughtered mixed-breed horses of both sexes. Our results showed a significant relationship between parasite burden and grading of histopathological lesions in the mucosa and submucosa. Hypertrophy of the circular muscle layer was found in infected horses. Moreover, enteric nervous system evaluation showed a significant injury of intestinal nervous elements in the horses with moderate to high parasitism expressed as an increase of degenerative-regressive changes in neuronal cells and a decrease in the number of myenteric ganglia and neuronal cells. These findings can help to clarify the pathogenesis of intestinal motility disorders associated with A. perfoliata infection in horses.     

Diffuse bilateral hemangiosarcoma of the uterus in a dog

A 15-year-old female mongrel dog showed abdominal swelling, marked hemorrhagic ascites and vulvar discharge, and ovariohysterectomy was performed. Grossly, the uterus was enlarged bilaterally without apparent mass formation. Histologically, the uterine muscular wall was composed of proliferated sinusoidal vessels. In some areas, irregular and small vessels proliferated markedly, while in others, pleomorphic and atypical tumor cells forming irregular vascular structures were predominant. From these findings, the case was diagnosed as diffuse bilateral hemangiosarcoma of the uterus that invaded to the ovary and broad ligament. The relationship between the tumor and angiomatosis was discussed.     

Subcutaneous Soft Tissue Sarcoma with Rhabdoid Features in a Dog

A nine-year-old male beagle dog had a white spherical mass in the subcutis of the left lumbar region. Microscopically, spindle to oval cells diffusely proliferated in the fibrous and myxoid stroma. Many neoplastic cells showed rhabdoid features or vacuolated cytoplasm. Immunohistochemically, the neoplastic cells were positive for vimentin and S100 and partly positive for neuron-specific enolase and glial fibrillary acidic protein but were negative for von Willebrand factor, desmin and α-smooth muscle actin. Ultrastructurally, the neoplastic cells had abundant cytoplasmic processes and desmosome-like structures. Cytoplasmic inclusions of rhabdoid-featured cells in HE sections were composed of aggregates of intermediate filaments, and cytoplasmic vacuoles were identified as an invagination of cytoplasm. Although malignant peripheral nerve sheath tumor was suggested according to these results, the present case was diagnosed as a soft tissue sarcoma with rhabdoid features due to a lack of identification of the basal lamina under electron microscopy.     

Pathologic and immunohistochemical findings in naturally occuring West Nile virus infection in horses

The pathologic and peroxidase immunohistochemical features of West Nile flavivirus (WNV) infection were compared in four horses from the northeastern United States and six horses from central Italy. In all 10 animals, there were mild to severe polioencephalomyelitis with small T lymphocyte and lesser macrophage perivascular infiltrate, multifocal glial nodules, neutrophils, and occasional neuronophagia. Perivascular hemorrhages, also noted macroscopically in two animals, were observed in 50% of the horses. In the four American horses, lesions extended from the basal nuclei through the brain stem and to the sacral spinal cord and were more severe than the lesions observed in the six Italian horses, which had moderate to severe lesions mainly in the thoracolumbar spinal cord and mild rhombencephalic lesions. WNV antigen was scant and was identified within the cytoplasm of a few neurons, fibers, glial cells, and macrophages. WNV infection in horses is characterized by lesions with little associated antigen when compared with WNV infection in birds and some fatal human infections and with other important viral encephalitides of horses, such as alphavirus infections and rabies.     

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.     

Histopathological and Immunohistochemical Characterization of Spontaneously Occurring Uterine Deciduomas in Young Adult Rats

Uterine deciduomas were found in two female virgin rats, a 15-week-old Lewis rat and a 7-week-old Sprague-Dawley rat. The firm white nodules were located at the base of unilateral uterine horns and were approximately 6 mm and 4 mm in diameter. Histopathologically, the nodules were composed of three areas, each with a distinct type of proliferating cells: large epithelioid decidual cells with round nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (antimesometrial region); compact spindle-shaped cells with oval nuclei and vacuolar cytoplasm (transitional region); and pleomorphic and spiny cells with round to oval nuclei and compact eosinophilic cytoplasm (mesometrial region). These cells proliferated in sheet-like arrangements and transformed into the other types of cells located in surrounding regions. Immunohistochemically, proliferating cells in all regions were strongly positive for proliferating cell nuclear antigen. The proliferating cells were positive for vimentin, and large decidual cells were positive for common acute lymphoblastic leukemia antigen 10, a marker of uterine interstitial cells. Large decidual cells were positive for α-smooth muscle actin and desmin, suggesting differentiation into muscular cells. Progesterone receptor was expressed in all cell types; however, estrogen receptor α was not expressed in the antimesometrial region. These extremely rare tumor-like nodules represent nonneoplastic lesions referred as decidual reactions of endometrial interstitial cells, and their biological behavior is that of a space-occupying benign tumor in young rats. Our cases might provide information as a historical control in toxicity and pharmacological studies in rats.     

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.     

Mixed Type of Malignant Mesothelioma in an Aged Male ICR Mouse

Multiple whitish nodules in the thoracic cavity at the site of the thymus were observed in a 101-week-old male ICR mouse. In a histopathological examination, the neoplastic cells were predominantly fusiform in shape and proliferated in sarcomatoid growth patterns. Some neoplastic cells showed epithelial growth patterns, such as the ductal structures. Mitotic figures were frequently seen, and small necrotic foci and invasion to adjacent thoracic organs were noted. In Alcian blue staining, bluish materials were observed between fusiform-shaped cells and in some of the lumens of the ductal structures. In immunohistochemistry, both fusiform-shaped and ductal structure-forming cells were positive for vimentin and weakly positive to positive for cytokeratin. Based on the aforementioned findings, the thoracic nodules were diagnosed as a mixed type of malignant mesothelioma. This case was thought to be rare because of the very low occurrence of spontaneous mesothelioma in mice.     

Microvascular circulation of the small intestine in horses.

The microvascular anatomic features of the small intestine was described by correlating results of microangiography, light microscopy, gross studies, and scanning electron microscopy of vascular replicas in 14 horses. After heparinization, the horses were euthanatized, a length of jejunum was transected, and blood was flushed free of the circulation, using isotonic NaCl solution. In six horses, the circulatory system was perfused with a modified radiopaque medium and evaluated radiographically. These sections were then evaluated by standard histologic methods. Sections from 8 horses were perfused with 1 of 2 types of plastics and studied grossly or by scanning electron microscopy. The marginal arterial arcade gives rise to vessels that enter the jejunum at the mesenteric angle. These vessels penetrated either directly, by branching and entering on both sides of the mesenteric angle, or supplying only 1 side of the mesenteric angle. All these vessels continued in the submucosa branching extensively, forming a submucosal plexus. This submucosal plexus supplied the tunica muscularis, tunica serosa, and the mucosa. Vessels within the 2 muscle layers ran parallel to the muscle fibers and, consequently, perpendicular to each other. The arterial supply to the mucosa penetrated the muscularis mucosae and branched to supply 2 mucosal capillary networks. An eccentrically placed arteriole penetrated the base of the villus and spiralled to the tip where it "fountained" into a mesh-like capillary network, which descended peripherally in the villus to drain via 1 to 3, but most commonly 2 venules. Venules from adjacent villi united and drained via the submucosal veins.(ABSTRACT TRUNCATED AT 250 WORDS)     

Complex apocrine carcinoma with dominant myoepithelial proliferation in a dog

A rare case of complex apocrine carcinoma displaying dominant myoepithelial proliferation developed in the right leg subcutis of a 10-year-old male dog. The major cell population consisted of diffusely proliferating p63-expressing neoplastic cells that were largely myoepithelial in origin co-expressing α-smooth muscle actin. A small portion of the cell population consisted of concomitant basal epithelial cells lacking α-smooth muscle actin expression. The minor population consisted of p63-negative apocrine gland cells that expressed cytokeratin 8. The myoepithelial cell population showed a rather stronger proliferation activity than did the apocrine epithelial population. Thus, this tumor might have been derived from basal epithelial cells characterized by more predominant myoepithelial differentiation than luminal apocrine epithelial differentiation.     

Sudden death attributable to exercise-induced pulmonary hemorrhage in racehorses: nine cases (1981-1983)

Pathologic changes are described in 11 horses that died during racing or training; 9 died of acute pulmonary hemorrhage (exercise-induced pulmonary hemorrhage), 1 died of exsanguination, and 1 died of CNS trauma. Cardiac lesions were not found in any horse. Severe engorgement of pulmonary vessels, with hemorrhage into alveoli, airways, interstitium, and subpleural tissues, was observed in all 9 horses that died of exercise-induced pulmonary hemorrhage. Infiltration of eosinophils and/or lymphocytes around vessels and airways was seen in 6 horses. Focally extensive fibrosis was observed in the pleura and interstitium of 6 horses, and collections of siderophages were seen in the fibrous tissue and in the airways. Focal occlusion of bronchioles with inspissated mucus, such as that associated with small airway disease, was found in 4 horses. Underlying respiratory tract lesions, particularly those associated with small airway disease or bronchiolitis, may have a role in fatal pulmonary hemorrhage.     

Masseter myodegeneration as a cause of trismus or dysphagia in adult horses

The medical records of eight horses with histological evidence of myodegeneration of the masseter muscles were examined. While they were alive their most common clinical signs had included difficulty in eating or opening their mouths, weight loss, difficulty in moving, and noticeable atrophy of the masseter muscles. The serum activities of muscle enzymes were abnormally high in all of the horses. Whole blood and/or liver selenium and vitamin E concentrations were less than the reference ranges in some of the horses. The lesions varied with the stage of the disease and consisted of swelling and discoloration, or muscle atrophy and fibrosis. Histologically, the muscle changes ranged from acute to subacute degeneration, with regenerative changes accompanying ongoing degeneration, to chronic degeneration with fibrotic replacement of muscle tissue. There were changes in the masseter muscle of all the horses, but some had widespread lesions in skeletal muscle, and a few also had myocardial lesions.     

Carcinosarcoma mimicking a feline injection‐site sarcoma in a cat

A 15‐year‐old spayed female domestic short‐haired cat with cutaneous/subcutaneous well‐circumscribed, alopecic mass approximately 25 × 30 mm in diameter, localized to the left shoulder region was brought to the veterinary surgery department. Despite the suggestive location and macroscopic appearance, feline injection‐site sarcoma was not suspected based on the cytologic examination of fine‐needle aspirates. The tumor was surgically resected, and tissue sections were evaluated microscopically. The tumor was found to be nonencapsulated with a distinct border between the neoplastic parenchyma and surrounding connective tissue. The neoplastic tissue consisted of 2 cell populations: elongated to spindle‐shaped cells arranged in bands and cords and malignant epithelial‐like cells. Both populations showed microscopic features of malignancy. Multinucleate giant cells with irregular cytoplasm were scattered among the neoplastic cells. The spindle‐shaped cells strongly expressed vimentin but did not express α‐smooth muscle actin (α‐SMA) or cytokeratin. Desmin was strongly expressed in about 0‐5% of cells. Epithelial‐like cells expressed cytokeratin, but not vimentin, desmin, or α‐SMA. Multinucleate giant cells expressed vimentin, but did not α‐SMA, desmin, or cytokeratin. Based on microscopic observations and IHC results, the final diagnosis was carcinosarcoma with histologic features compatible with feline injection‐site sarcoma, but without the clinical aggressiveness of this tumor.     

Hematogenous metastasis of embryonal rhabdomyosarcoma originating from skeletal muscle in a young dog.

An 8-month-old, intact male Golden Retriever with a history of left forelimb lameness for 2 months was presented to the Veterinary Medical Teaching Hospital of Konkuk University (Seoul, Korea). Results of a physical examination revealed a mass in the left axillary region. A thoracic radiography showed an osteolytic lesion in the scapula and the presence of a soft tissue density from the thoracic wall to the scapula. A computerized tomography revealed a mass invading into the scapula, and small nodules in the lung that suggested metastasis. At necropsy, a pale-yellow, irregular, firm, 8 x 10 x 5 cm mass extended from axillary region and destroyed the scapular. In addition, small nodules were noted in the lung. On microscopic examination, the mass consisted of round-to-oval cells, with eccentrically located hyperchromatic nuclei and eosinophilic cytoplasm in fibromyxoid stroma. Tumor cells were observed in blood vessels in the primary mass. Tumor cells strongly expressed vimentin, desmin, and myoglobin. In phosphotungstic acid-hematoxylin staining, cross-striations were detected in rhabdomyoblasts. In periodic acid-Schiff reaction, only a few cells were detected. The diagnosis was primary rhabdomyosarcoma of the appendicular muscle of a young dog. The tumor presumably originated in the skeletal muscle of the limb, invaded into the adjacent scapular bone, and metastasized to the lung.     

Glomus tumor in the digit of a cat

A solitary mass approximately 1.5 x 2 cm located on the outer side of the third digit of the left forepaw of a 7-year-old male cross-breed cat was examined pathologically. The excised tumor mass was hard and white and located within the deep dermis and subcutis. Histopathologically, the mass consisted of a mixed population of small round epithelioid cells arranged in ribbon- or cordlike structures and spindle-shaped cells forming loose irregular bundles in a mucinous stroma. The epithelioid cells were often arranged around small blood vessels. Neoplastic cells were intensely positive for vimentin and alpha smooth muscle actin and negative for keratin, desmin, S-100 protein, and neuron-specific enolase. Based on these pathologic features, the tumor was diagnosed as a glomus tumor, a neoplasm not previously reported in cats and extremely rare in animals.     

Intramuscular desmoid tumor (musculoaponeurotic fibromatosis) in two horses.

Intramuscular desmoid tumors (musculoaponeurotic fibromatosis) were discovered in two young adult horses. The tumor in one horse was in the lateral cervical musculature, and that in the second horse occurred in the pectoral musculature. Histopathologic features were similar in both horses and included proliferation of fibroblasts and cells expressing muscle actin (myofibroblasts), with extensive dissecting fibrosis within muscle. These features are similar to those of desmoid tumors in humans, particularly those also known as musculoaponeurotic fibromatosis. Dissection of these lesions revealed a single central (horse No. 1) or multiple central (horse No. 2) fluid-filled cavities with associated sterile inflammation. The presence of these cavities supports the hypothesis that equine desmoid tumors are traumatic in origin, possibly occurring at sites of injections or bursal rupture. Surgical excision of the tumor in horse No. 1 was apparently curative, but the extent of the tumor in horse No. 2 precluded surgical excision.     

Immunohistochemical characterization of tumor cells and inflammatory infiltrate associated with cutaneous melanocytic tumors of Duroc and Iberian swine

The immunophenotype of tumor cells and inflammatory infiltrate associated with cutaneous melanocytic lesions (29 melanocytomas, two malignant melanomas, and 23 residual lesions) from 54 adult Iberian and Iberian x Duroc pigs were examined using a panel of nine antibodies. All neoplastic cells were vimentin+, cytokeratin-, and alpha-1-antitrypsin- and the majority were S100+, whereas all pigmented macrophages were vimentin+, cytokeratin-, and S100- and most expressed alpha-1-antitrypsin. Regressing tumors were characterized by zones with low density of neoplastic cells accompanied by heavy infiltration of CD3+ T lymphocytes, whereas zones with high density of neoplastic cells showed very low numbers of CD3+ T lymphocytes. The infiltrate of CD79a+ B cells and IgG, IgM, and IgA plasma cells was low. The majority of lymphocytes of the peri- and intratumoral infiltrate were major histocompatibility complex class II+, but neoplastic cells did not express class II antigen. The 17 residual lesions examined were composed of macrophages containing abundant melanin pigment and low to moderate numbers of CD3+ T lymphocytes. The results of the present study suggest that the local cellular immune response plays a crucial role in the host response that induces regression of cutaneous melanomas and melanocytomas of the Iberian and crossbred Iberian x Duroc pigs.     

Establishment of a new canine cell line (CCT) originated from a cutaneous malignant histiocytosis

A new canine cell line, named CCT, was established from the cutaneous malignant histiocytosis in a 4-year-old male Borzoi. CCT proliferated with loose adherence and doubling time was approximately 30 hr. When co-cultured with latex beads, CCT phagocytized beads vigorously. Lysozyme and vimentin were positive by immunostaining, and non-specific esterase and acid phosphatase were positive by cytochemical staining. These features indicated the cells had a histiocytic nature. Furthermore, by subcutaneous injection to nude mice CCT could successfully form tumors with the morphological and immunohistochemical features similar to the original tumor.     

Spontaneous extraskeletal osteosarcoma in the neck skeletal muscle of a Crlj:CD1 (ICR) mouse

Extraskeletal osteosarcoma is extremely rare in humans and animals, especially in rodents. This is the first case report on spontaneous extraskeletal osteosarcoma in the neck skeletal muscle of a Crlj:CD1 (ICR) mouse (36 weeks, dead). Necropsy revealed a solid white mass located in the neck skeletal muscle (scalenus muscle). Histological examination showed that the tumor consisted of atypical polygonal cells, a small osteoid clump, and bone tissue. Mitotic figures were observed. Serial sections showed that neoplastic cells lacked clear invasive proliferation to adjacent normal skeletal muscle and continuity with normal bone tissue. Immunohistochemical analysis showed that the neoplastic cells were positive for osteocalcin, osterix, vimentin, and S-100. Based on these results, the tumor was diagnosed as extraskeletal osteosarcoma in the neck skeletal muscle.