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.

A case series of urinary bladder rhabdomyosarcoma in seven dogs.

Background: Juvenile urinary bladder rhabdomyosarcoma (ubRMS) is a known entity; however, literature regarding its clinical behavior and endoscopic features is scarce. The aim of this study was to describe clinical and endoscopic features, and outcomes of ubRMS in dogs. Case Description: Dogs undergoing transurethral endoscopy and with a histological diagnosis of ubRMS were retrospectively collected. Seven dogs with a median age of 18 months (range 6-32 months) were included in this retrospective, multicenter, and descriptive study. Median tumor size was 58 mm (range 30-65 mm), and tumor location was bladder neck in three cases, trigone in two cases, and bladder body in two cases. Two dogs had monolateral ureteral obstruction. Two dogs presented with regional lymphadenopathy and one dog had lung lesions suggestive of metastatic disease. A grape-like mass was reported in four cases and solid in two, with variable consistency (two friables, two firms, and two not reported). Tumor treatments included surgery in three cases, surgery, and adjuvant doxorubicin in one case, and palliative therapy in three cases. The overall median survival time (ST) was 45 days. STs were shorter (range 20-45 days) for dogs treated with palliative care than for dogs treated with curative-intent treatment (range 70-120 days). Conclusion: ubRMS should be considered as a differential diagnosis in young dogs presenting with bladder masses. In this study, ubRMS confirmed its aggressive clinical behavior. Surgery and chemotherapy seem to increase STs but the prognosis remains poor.

A primary multiple pleomorphic rhabdomyosarcoma of the heart in an adult dog.

BACKGROUND: Heart tumors are rare in dogs. They can be benign or malignant. Clinical signs depend primarily on the location of the tumor and its effect on blood flow. CASE PRESENTATION: An eleven-year-old crossbreed male dog lethargic and anorectic for previous 3 days was presented to the veterinary clinic. The focused ultrasound assessment with sonograms in trauma (FAST) revealed multiple tumors in the heart which were then confirmed in echocardiographic examination performed by a veterinary cardiologist. Due to the poor general condition and grave prognosis, the dog was humanely euthanized. The autopsy revealed numerous intracardiac tumors in all four heart chambers. No proliferative changes were found in other organs either in thoracic or abdominal cavity. Immunohistochemical examination was performed using formalin-fixed, paraffin-embedded tissue from heart masses. The antibodies against myoglobin, desmin, smooth muscle actin, vimentin, CD34, S100, and pan-cytokeratin (AE1/AE3) were used. Microscopically, the tumor was composed of fascicles of spindle-shaped cells with pale eosinophilic cytoplasm with round, oval, and focally elongated nuclei and one or two prominent nucleoli. The tumor cells showed strong diffuse cytoplasmic immunopositivity for myoglobin and vimentin and focal staining for desmin. Immunostainings for smooth muscle actin-SMA, CD34, pan-cytokeratin, S-100 protein were negative. The immunohistochemical staining pattern confirmed rhabdomyosarcoma. CONCLUSIONS: This is the first description of the primary multiple heart rhabdomyosarcoma in a dog.

Invasive spindle-cell rhabdomyosarcoma with osteolysis in a dog: case report and literature review.

Rhabdomyosarcoma (RMS), a malignant mesenchymal neoplasm derived from skeletal muscle, is relatively rare in both human and veterinary medicine. Here we report an unusual case of invasive spindle-cell RMS (SCRMS) with bone infiltration and pathologic fracture in a 3.5-y-old intact female Bulldog. Radiographically, a large, predominantly osteolytic mass in the tibia and fibula of the left hindlimb had features typical of a malignant primary bone tumor. Clinically, osteosarcoma was suspected, and the leg was amputated. Histologically, the mass was composed of loosely interwoven spindle-cell fascicles; tumor cells were fusiform with cigar-shaped nuclei and abundant eosinophilic cytoplasm. The neoplastic cells were strongly immunopositive for vimentin, muscle-specific actin, desmin, myogenin, and myoD1. Invasive SCRMS with osteolysis was diagnosed based on the histologic examination and immunohistochemical (IHC) stains. The dog was alive without any evidence of local recurrence or distant metastasis 18 mo post-surgery. RMS should be included in the differential diagnosis when osteolysis occurs; IHC staining confirmation is of great value for definitive diagnosis and treatment planning.

Rhabdomyosarcoma on the Forelimb of a Common Musk Turtle (Sternotherus odoratus).

Malignant mesenchymal tumours are only rarely reported in turtles. In the present case, an 8-year-old female common musk turtle (Sternotherus odoratus) was presented with a solid, reddened, non-mobile mass on the right forelimb. The mass had a thin, membranous lining and a grey-white cut surface. Histological examination revealed a cell-rich, focally infiltrative neoplasm consisting of spindloid tumour cells arranged in bundles and streams. Rarely, indistinct cytoplasmic cross-striations were seen in the neoplastic cells. Transmission electron microscopy revealed cytoplasmic, disorganized muscle fibrils and haphazardly arranged, attenuated Z-lines in the neoplastic cells. The histological, histochemical and ultrastructural findings led to the diagnosis of a rhabdomyosarcoma. This is the first description of rhabdomyosarcoma in a freshwater turtle.

Evaluation of Myogenin and MyoD1 as Immunohistochemical Markers of Canine Rhabdomyosarcoma.

Canine rhabdomyosarcoma (RMS) presents a diagnostic challenge due to its overlapping histologic features with other soft tissue sarcomas. The diagnosis of RMS currently relies on positive immunohistochemical (IHC) labeling for desmin; however, desmin expression is also observed in non-RMS tumors. Myogenin and MyoD1 are transcription factors reported to be sensitive and specific IHC markers for human RMS, but they are not widely used in veterinary oncology. The goals of this study were to develop an IHC protocol for myogenin and MyoD1, evaluate myogenin and MyoD1 labeling in canine RMS, and report clinical outcomes. Sixteen cases of possible RMS were retrospectively evaluated. A diagnosis of RMS was confirmed in 13 cases based on histological features and immunolabeling for myogenin and MyoD1, with the aid of electron microscopy in 2 cases. Desmin was negative in 3 cases of RMS. Two cases were of the sclerosing variant. The median age of dogs with RMS was 7.2 years. Anatomic tumor locations included previously reported sites such as bladder, larynx, heart, and orbit, as well as other locations typical of soft tissue sarcomas. Survival ranged from 47 to 1480 days for 5 dogs with available data. This study demonstrated that MyoD1 and myogenin should be included with desmin as part of a diagnostic IHC panel for canine RMS. Utilization of these antibodies to improve the accuracy of canine RMS diagnosis will ultimately allow for better characterization of the biological behavior and clinical outcomes of this disease, providing the groundwork for future comparative investigations in canine RMS.

Neuropathogenicity of newly isolated avian leukosis viruses from chickens with osteopetrosis and mesenchymal neoplasms.

ABSTRACT The prototype fowl glioma-inducing virus (FGVp) causes fowl glioma and cerebellar hypoplasia in chickens. In this study, we investigated whether a strain of avian leukosis virus (ALV), associated with avian osteopetrosis and mesenchymal neoplasms, is able to induce fowl glioma. We encountered avian osteopetrosis and mesenchymal neoplasms, including myxosarcoma and rhabdomyosarcoma, in Japanese native chickens used for both egg-laying and meat production. These birds were also affected by non-suppurative encephalitis and glioma in their brains. Four ALV strains (GifN_001, GifN_002, GifN_004, GifN_005) were isolated, and a phylogenic analysis of envSU showed that these isolates were classified into different clusters from FGVp and the variants previously reported. Whereas the envSU shared a high identity (94.7%) with that of Rous sarcoma virus (strain Schmidt-Ruppin B) (RSV-SRB), the identity between envTM of GifN_001 and that of FGVp was high (94.5%), indicating that GifN_strains may emerge by recombination between FGVp and other exogenous ALVs. Specific-pathogen-free chickens inoculated in ovo with GifN_001 revealed fowl glioma and cerebellar hypoplasia. These results suggest that the newly isolated strains have acquired neuropathogenicity to chickens.

Biological behaviour and ezrin expression in canine rhabdomyosarcomas: 25 cases (1990-2012).

There are few published reports of canine rhabdomyosarcomas. In human paediatrics, rhabdomyosarcomas account for 5%-10% of all tumours and >50% of soft tissue sarcomas. They have an aggressive biologic behaviour; most patients develop diffuse metastatic disease. Ezrin, a cytoskeleton linker protein, has been correlated with metastasis in a number of tumours, including rhabdomyosarcomas. The goal of this study was to describe dogs with non-urinary rhabdomyosarcomas including clinical findings, ezrin expression and outcome. Twenty-five dogs with rhabdomyosarcomas were identified from two institutions' databases. Signalment, primary tumour location, cytologic and histologic findings, metastatic sites, treatments, survival time and necropsy results were recorded. Immunohistochemical staining for ezrin expression was performed on archived samples; cellular localization of ezrin was characterized. The mean and median age of all patients was 4.3 and 2 years, respectively. Subcutaneous and retrobulbar/orbital were the most common primary tumour locations. Sixteen dogs had metastatic disease at diagnosis. Three dogs presented with diffuse disease where a primary tumour could not be identified. A round cell tumour was the initial diagnosis in 32% of cases, and 76% of cases required immunohistochemistry to establish the diagnosis. The median survival was 10 days. Twenty-one cases had archived samples available for ezrin staining; all but one was positive and exhibited both membranous and cytoplasmic localization. Rhabdomyosarcomas occur in young dogs, may have a round cell appearance, and exhibit aggressive biologic behaviour. Given ezrin's defined role in metastasis, its observed expression in the tumours in this study suggest its possible role in canine rhabdomyosarcoma's aggressive biologic behaviour.

Clinical, pathological and therapeutic findings on lingual rhabdomyosarcoma in a dog - case report / Achados clínicos, patológicos e terapêuticos do rabdomiossarcoma em cão - relato de caso

The biological behaviour of the tumours vary according to the species in which they occur, its location within the cavity, clinical stage and histopathological nature. Lingual neoplasms are generally uncommon in companion animals. Rhabdomyosarcomas are malignant, solid, aggressive formations with high metastatic potential. The clinical signs are variable and a definitive diagnosis can only be reached through histopathological analysis of biopsy and necropsy specimen. In some cases, immunohistochemical study may be needed to confirm the diagnosis. This paper aims to highlight important points about this uncommon condition in dogs, using a case report of lingual rhabdomyosarcoma, which showed no evidence of metastasis after diagnosis, nor of local recurrence after surgical excision with a wide safety margin. It was concluded that early diagnosis, the correct interpretation of the complementary tests and the appropriate therapeutic approach contributed to improving the quality of life and survival of the patient in question.(AU)

O comportamento biológico dos tumores varia de acordo com a espécie animal, a localização na cavidade, a fase clínica e a natureza histopatológica. As neoplasias orais são geralmente incomuns em animais de companhia. Os rabdomiossarcomas são formações malignas, sólidas e agressivas, com alto potencial metastático. Os sinais clínicos são variáveis e o diagnóstico definitivo só pode ser alcançado por meio da análise histopatológica do material colhido. Em alguns casos, o estudo imuno-histoquímico pode ser necessário para confirmar o diagnóstico. Este trabalho tem como objetivo destacar pontos importantes sobre essa condição incomum em cães, utilizando um relato de caso de rabdomiossarcoma lingual, no qual não se evidenciaram metástases após o diagnóstico, nem recorrência local após a excisão cirúrgica com ampla margem de segurança. Concluiu-se que o diagnóstico precoce, a correta interpretação dos exames complementares e a abordagem terapêutica adequada contribuíram para melhorar a qualidade de vida e a sobrevida do paciente em questão.(AU)

Primary Meningeal Rhabdomyosarcoma of the Spinal Cord of a Young Dog with Neuromelanocytosis and Multiple Cutaneous Neurofibromas.

A 7-week-old male black Labrador retriever puppy was presented for post-mortem examination following progressive hindlimb paralysis and multiple masses within the skin. A highly compressive and infiltrative intradural mass was found within the T9-T11 spinal cord. Microscopical and immunohistochemical analysis revealed features compatible with spindle cell rhabdomyosarcoma (RMS). The adjacent spinal cord had numerous melanin-containing cells, arranged in small nodules, predominantly within the grey matter (proposed term of 'micronodular neuromelanocytosis') and the left lateral thorax had multifocal dermal neurofibromas. In this case, the constellation of proliferative/neoplastic lesions represents a unique case presentation with unclear aetiology. Primary canine meningeal RMS of the spinal cord has not been reported previously and represents a novel differential diagnosis for spinal tumours of young dogs. Moreover, such cases should be assessed for the presence of additional congenital abnormalities.

Uterine metastatic rhabdomyosarcoma in a scimitar-horned oryx (Oryx dammah).

A 13-year-old female scimitar-horned oryx (Oryx dammah) died after progressive anorexia, weight loss, and depression. The necropsy showed that the retroperitoneum was compressed by a large white-to-tan uterine mass and on several sections of the mass, the uterine wall was markedly thickened because of ill-defined transmural tumor tissue. Metastatic nodules were detected in the omentum, mesentery, diaphragm, and lung. The genital tract and pulmonary and abdominal nodules exhibited highly pleomorphic sarcoma. The primary and metastatic neoplastic cells showed positive results for vimentin, desmin, and sarcomeric actin, and negative results for smooth muscle actin. Uterine metastatic rhabdomyosarcoma was diagnosed on the basis of the gross, histopathology and immunohistochemistry results.

Identification of tumor-initiating cells derived from two canine rhabdomyosarcoma cell lines.

Cancer stem cells or tumor-initiating cells (TICs) are a small subpopulation of cells that have the capacity to self-renew, differentiate and initiate tumors. These cells may function in tumor initiation, aggression and recurrence. Whether spheres derived from canine rhabdomyosarcoma cells have stem cell-like properties is unclear. We induced sphere formation in the canine rhabdomyosarcoma cell lines, CMS-C and CMS-J, and characterized the spheres in vitro and in vivo. Sphere-forming cells were more resistant to vincristine, mitoxantrone and doxorubicin than adherent cells. Xenograft transplantation demonstrated that 1 × 103 sphere-forming cells derived from CMS-C were sufficient for tumor formation. The sphere assay showed that the sphere-forming cells were present in these tumors. These results suggest that the spheres derived from canine rhabdomyosarcoma cells may possess characteristics of TICs. This study provides the foundation for elucidating the contribution of TICs to rhabdomyosarcoma tumorigenesis.

Subcutaneous rhabdomyosarcoma in an old rabbit.

An 11-year-old castrated male rabbit presented with a subcutaneous mass in the right hind limb. The mass comprised solid and myxoid areas. Solid areas were characterized by a storiform or interlacing pattern of spindle cells, strap cells, multinucleated giant cells and round cells with eccentrically located nuclei, whereas the myxoid areas were composed predominantly of elongated fusiform cells with hyperchromatic nuclei embedded in Alcian Blue-positive myxoid stroma. Immunohistochemically, tumor cells in both areas were positive for desmin and vimentin. Ultrastructurally, the tumor cells in the solid areas had abundant myofilaments with electron dense Z-band structures. Based on these pathological findings, this case was diagnosed as rhabdomyosarcoma in a rabbit.

Rhabdomyosarcoma in a Silver Carp.

Rhabdomyosarcoma is a primitive neoplasm that originates from skeletal muscle progenitor cells. In a routine inspection of a cyprinid farm in southwestern Iran, an approximately 2-year-old female Silver Carp was observed to have a raised mass located on the dorsolateral surface just caudal to the head. Macroscopic examination revealed a firm irregular fleshy pink mass (5 × 4 cm, depth = 3 cm) that appeared to arise from the subcutaneous musculature. Histologic sections were prepared using routine methods and separate sections were stained with hematoxylin-eosin and Massons' trichrome. Microscopically, the tumor mass was composed of spindle cells that were densely packed and arranged in long interwoven bundles. The nuclei were vesicular and oval to elongated or cigar-shaped. Nuclear pleomorphism and multinucleate tumor giant cells were clearly evident. The neoplastic cell cytoplasm was eosinophilic with indistinct cell margins, and clear cross striations were observed in fibrils. The striated fibrils stained diffusely red with Masson's trichrome. This account represents the first reported occurrence of rhabdomyosarcoma in Silver Carp Hypophthalmichthys molitrix. Received July 10, 2015; accepted February 4, 2016.

Canine orbital rhabdomyosarcoma: a report of 18 cases.

PURPOSE: To describe clinical and pathological features of canine orbital rhabdomyosarcoma (COR). METHODS: Retrospective review of patients with COR from the archives of the Comparative Ocular Pathology Laboratory of Wisconsin and the University of Wisconsin Veterinary Medical Teaching Hospital (1983-2014). RESULTS: Eighteen cases of COR were identified, all diagnosed in an 8-year period (2006-2014). Affected dogs were typically young (range 1-8; median 2 years), and both sexes were equally represented. Common clinical signs included exophthalmos (16/18) with dorsolateral deviation of the globe (10/18) and elevation of the nictitans (12/18). Ultrasonography, performed in nine cases, revealed an orbital mass with mixed echogenicity and posterior globe indentation. Advanced imaging, performed in nine cases, demonstrated a soft tissue mass with variable contrast enhancement and lysis of the orbital bones (5/9). Histologically, all tumors were subclassified as embryonal rhabdomyosarcoma. All neoplasms demonstrated positive immunohistochemical labeling for desmin, and 14/18 were positive for skeletal muscle actin. Follow-up information was available for 15/18 cases. Older dogs, aged 6-8 years, had no clinical signs of recurrence or metastasis 8-13 months postdiagnosis (4/4). Most younger dogs (9/11), aged 1-4 years, were euthanized within 6 months (median 2.5 months) of diagnosis due to recurrence at the surgical site (5/9) and/or metastasis (5/9). CONCLUSIONS: Canine orbital rhabdomyosarcoma is a highly malignant neoplasm in juvenile dogs, but may be amenable to surgical resection in older dogs. This duality in biologic behavior may reflect differences in tissue of origin between juvenile onset tumors and adult onset tumors.

Rhabdomyosarcoma of Soft Tissues in an Adult Brook Trout (Salvelinus fontinalis).

This report describes a spontaneously arising rhabdomyosarcoma of soft tissues in a brook trout (Salvelinus fontinalis). The lesion was examined by means of histology, immunohistochemistry (IHC) and transmission electron microscopy (TEM). The cross-reactivity of the primary antibodies used in the IHC was investigated in silico using the Protein Blast system. Microscopically, the lesion appeared as a 'small round cell' undifferentiated sarcoma with rare myotube formation. IHC identified expression of sarcomeric actin and vimentin and these molecules showed the highest protein sequence identity. Lower protein sequence identity coincided with negative immunolabelling for desmin, MyoD1, myogenin and CD3. TEM revealed myofibrils, but without a defined sarcomeric architecture. The diagnosis of solid alveolar rhabdomyosarcoma of soft tissues was achieved on the basis of histological and ultrastructural findings.

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.

Retrobulbar rhabdomyosarcoma in a neotropical peregrine falcon (Falco peregrinus cassini).

A mild swelling of the left periorbital was detected on a routine physical exam of a healthy captive adult peregrine falcon. Despite treatment, the swelling did not subside and within twenty-five days was causing significant exophthalmia and medial deviation of the left globe. A retrobulbar fusiform cell sarcoma was diagnosed with histopathology, then light microscopy and immunohistochemical staining confirmed the diagnosis of a rhabdomyosarcoma.

A comparative review of canine and human rhabdomyosarcoma with emphasis on classification and pathogenesis.

Rhabdomyosarcomas are a diverse group of malignant mesenchymal neoplasms exhibiting variable levels of differentiation toward skeletal myocytes. Neoplastic cells may resemble relatively undifferentiated myoblasts, satellite cells, or more differentiated elongated spindle cells and multicellular myotubes. In veterinary medicine, classification into subtypes and variants is based on an outdated system derived from human pathology and is solely based on histologic characteristics. In contrast, classification of human rhabdomyosarcoma is based on histologic, immunohistochemical, and molecular diagnostic techniques, and subclassification has clinical and prognostic relevance. Relevance of tumor subtyping has not been established in veterinary medicine. Recent discoveries of components of the molecular pathogenesis and genomes of human rhabdomyosarcomas have led to new diagnostic techniques and revisions of the human classification system. The current classification system in veterinary medicine is reviewed in light of these changes. Diagnosis of rhabdomyosarcoma using histopathology, electron microscopy, and the clinical aspects of human and canine rhabdomyosarcomas is compared. The clinical features and biologic behavior of canine rhabdomyosarcomas are compared with canine soft tissue sarcomas.