Fetal rhabdomyoma in a Thoroughbred filly.

A newborn Thoroughbred filly presented with a large mass located on the ventro-rostral aspect of the mandible. The mass was surgically removed under general anaesthesia. Upon gross examination, the mass was well circumscribed with a heterogeneous lobulated appearance. The results of histopathology and immunohistochemistry were consistent with a diagnosis of congenital fetal rhabdomyoma. On follow-up at six months post-surgical excision, no abnormalities were noted on clinical examination.

Extracardiac adult-type rhabdomyoma-Report of two cases in dogs.

This report describes the cytologic, histopathologic, and immunohistochemical features of adult-type rhabdomyoma located within the subcutaneous tissue in a 14-year-old female Border Collie (thigh) and a 13-year-old male Mongrel (flank). In both cases, fine-needle aspiration biopsy revealed cluster-forming, epithelial-like polygonal cells with abundant foamy cytoplasm, and moderate to marked anisocytosis and anisokaryosis; therefore, an epithelial tumor was suspected. After surgical excision, tumors underwent histopathologic examination with additional immunohistochemistry. Both tumors were well-demarcated and located within the subcutaneous tissue in the vicinity of the cutaneous muscle. The tumor mass consisted of densely packed round or polygonal cells with distinct vacuolation of the cytoplasm. Tumor cells expressed vimentin, desmin, and NSE and were cytokeratin and α-SMA negative. Based on histologic features and immunophenotyping, adult-type rhabdomyoma was diagnosed in both cases. This study highlights that the cytologic features of rhabdomyoma can be misleading and may suggest an epithelial tumor.

Cardiac Rhabdomyoma in Four Göttingen Minipigs.

Göttingen minipigs are increasingly used as an alternative large animal model in nonclinical toxicology studies, and proliferative lesions in this species are rare. Here, we report four cases of cardiac rhabdomyoma in Göttingen minipigs, an incidental and benign mass in the heart. Three cases lacked gross observations and had a microscopic nodule in either the left ventricle or interventricular septum. The last case had a large, firm, raised nodule on a left ventricular papillary muscle noted at necropsy, with additional microscopic intramural masses in the left ventricular wall. In all cases, microscopic evaluation revealed well-circumscribed, expansile nodules composed of bundles of large, highly vacuolated, ovoid to polygonal cells with variable cytoplasmic processes radiating from a centrally located nucleus. Cells displayed patchy accumulation of intracytoplasmic, PAS-positive material and haphazardly arranged cytoplasmic cross-striations. There was no evidence of cardiac insufficiency or other data to suggest the masses were clinically meaningful. Cardiac rhabdomyomas have been reported in meat-hybrid swine, with a breed predisposition in red wattle. This lesion is well established in guinea pigs, but documentation in other laboratory species used in toxicologic studies is limited to two beagle dogs. To our knowledge, this is the first report of spontaneous cardiac rhabdomyoma in Göttingen minipigs.

Cardiac pathology and molecular epidemiology by avian leukosis viruses in Japan.

Epidemiological studies suggest that retroviruses, including human immunodeficiency virus type 1, are associated with cardiomyopathy and myocarditis, but a causal relationship remains to be established. We encountered unusual cardiomyocyte hypertrophy and mitosis in Japanese native fowls infected with subgroup A of the avian leukosis viruses (ALVs-A), which belong to the genus Alpharetrovirus of the family Retroviridae and mainly induce lymphoid neoplasm in chickens. The affected hearts were evaluated by histopathology and immunohistochemistry, viral isolation, viral genome sequencing and experimental infection. There was non-suppurative myocarditis in eighteen fowls and seven of them had abnormal cardiomyocytes, which were distributed predominantly in the left ventricular wall and showed hypertrophic cytoplasm and atypical large nuclei. Nuclear chains and mitosis were frequently noted in these cardiomyocytes and immunohistochemistry for proliferating cell nuclear antigen supported the enhancement of mitotic activity. ALVs were isolated from all affected cases and phylogenic analysis of envSU genes showed that the isolates were mainly classified into two different clusters, suggesting viral genome diversity. In ovo experimental infection with two of the isolates was demonstrated to cause myocarditis and cardiomyocyte hypertrophy similar to those in the naturally occurring lesions and cardiac hamartoma (rhabdomyoma) in a shorter period of time (at 70 days of age) than expected. These results indicate that ALVs cause myocarditis as well as cardiomyocyte abnormality in chickens, implying a pathogenetic mechanism different from insertional mutagenesis and the existence of retrovirus-induced heart disorder.

Laryngeal rhabdomyoma in a dog.

A 3-year-old, female spayed Australian Shepherd dog was presented to Veterinary Healthcare Associates in Winter Haven, FL with a history of respiratory stridor, difficulty swallowing, and a change in bark for approximately 3 months. Radiographs revealed a soft tissue mass caudal to the epiglottis. Oral and computerized tomographic (CT) examinations were performed under general anesthesia and revealed a small firm mass in the caudal larynx on the right side. Cytologic evaluation of a fine-needle aspirate of the mass revealed cells consistent with a rhabdomyoma, oncocytoma, or granular cell tumor. Histopathologic interpretation was rhabdomyoma or oncocytoma. Histochemical staining with periodic acid-Schiff was mostly negative with a low number of weakly positive cells and with phosphotungstic acid-hematoxylin was strongly positive with visible cross striations. Tumor cells did not express pancytokeratin AE1/AE3, were strongly immunoreactive for myoglobin and muscle-specific actin, and did not express vimentin except for a low number of weakly immunoreactive cells. These findings confirmed a diagnosis of rhabdomyoma. Primary neoplasia of the larynx is rare, and widely varying types of neoplasms have been documented in this location. Due to the cytologic and histologic similarities between rhabdomyoma, oncocytoma, and granular cell tumor, these neoplasms should be differentiated using histochemical staining and immunohistochemical analysis.

Proposing the term purkinjeoma: protein gene product 9.5 expression in 2 porcine cardiac rhabdomyomas indicates possible purkinje fiber cell origin.

Rhabdomyomas, defined as rare benign tumors of striated muscle, predominantly occur in the myocardium. In veterinary medicine, cardiac rhabdomyomas have rarely been reported but most frequently in pigs as an incidental finding. In the present case report, multiple circumscribed nodules found in the myocardium of 2 pigs were composed of large, vacuolated, glycogen-loaded cells. They expressed vimentin and desmin, neuron-specific enolase, and atrial natriuretic peptide. In addition, these cells expressed protein gene product 9.5, a marker for neuronal tissue and Purkinje fiber cells, in contrast to adjacent myocytes. The present findings-especially, the protein gene product 9.5 immunoreactivity-provide further evidence for the Purkinje fiber cell origin of the porcine myocardial proliferation. Therefore, the term purkinjeoma or purkinjeomatosis is proposed for cardiac rhabdomyoma in pigs.

A rhabdomyoma within a multilocular thymic cyst in a p53-null mouse.

A 9-month-old p53-null female mouse was found dead in its cage. At necropsy, a large thymic mass encompassed the heart. Microscopically, the mass was composed of numerous varying-sized cysts lined with simple squamous epithelial cells to columnar ciliated cells. Also present within this mass was a large aggregate of loosely arranged fusiform-shaped cells. These cells also were found in smaller numbers in the connective tissue surrounding the cysts. The larger aggregate of fusiform cells was positive for desmin and S-100 and negative for smooth muscle actin. Electron microscopy revealed well-formed Z lines and I bands of skeletal muscle phenotype. A diagnosis of rhabdomyoma within a congenital multilocular thymic cyst was made. The thymus contains a small population of myoid cells, which should be taken in consideration when evaluating thymic tumors.

Canine cardiac rhabdomyoma.

A well-circumscribed, expansile, and nonencapsulated cardiac rhabdomyoma composed of tightly arranged, large, variably sized, ovoid to irregular, swollen myocytes with deeply eosinophilic cytoplasm and varying degrees of cytoplasmic vacuolation was detected in an eight- to nine-month-old female beagle dog in a routine toxicology study. By histochemistry, the neoplasm was periodic acid-Schiff positive. By immunohistochemistry (IHC), neoplastic cells were positive for desmin and myoglobin and negative for vimentin and smooth muscle actin. Spontaneous lesions in the heart of young beagle dogs are rare in drug safety studies. On the basis of histopathology, histochemistry, and IHC findings, a diagnosis of cardiac rhabdomyoma was made. Cardiac rhabdomyoma is one of the most frequently occurring primary tumors of the heart and, by far, the most common neoplasm in human infants and children. To our knowledge, this is the first report of the canine cardiac rhabdomyoma.

Cardiac rhabdomyoma in a juvenile fallow deer (Dama dama).

A cardiac rhabdomyoma is described in a 6-wk-old captive fallow deer (Dama dama) that died suddenly without previous clinical signs. The tumor was characterized by multiple nodules composed of large atypical vacuolated myoblastic cells. As previously reported in humans and other animal species, there is compelling evidence that the cardiac rhabdomyoma is a congenital developmental anomaly rather than a true neoplasm. To our knowledge, this is the first report of a cardiac tumor and a rhabdomyoma in a cervid species.

Congenital fetal rhabdomyoma in a foal.

An Appaloosa filly was born with a ventral midline, approximately 8 x 12 x 15 cm subcutaneous cervical mass. The nonencapsulated mass was composed of interlacing and haphazard bundles of spindle cells on moderate to abundant loose myxomatous stroma. A moderate number of cells showed cross striations with minor nuclear variation and a low mitotic rate. Immunohistochemical staining for myoglobin, desmin, actin, vimentin, and S-100 was positive and negative for glial fibrillar antigen and keratin. Rhabdomyomas are rare benign tumors of striated muscle. Rhabdomyomas described previously in the veterinary literature are analogous to the "adult form" of human rhabdomyoma. This is the first report of a veterinary case that 1) clinically and histologically parallels the "fetal form" in human rhabdomyoma and 2) describes a congenital extracardiac rhabdomyoma.

Laryngeal rhabdomyoma in a dog.

A 4-year-old spayed female Golden Retriever was presented for investigation of progressive loss of bark, continuous panting and increased upper respiratory noise. Examination of the larynx and pharynx under general anaesthesia identified a spherical 5 x 3 cm mass involving the right arytenoid cartilage. Cytological examination of fine needle aspirates from the mass suggested the tumour was a carcinoma, however histological examination in association with immunoperoxidase and histochemical staining identified the mass as a laryngeal rhabdomyoma.

Intra-atrial rhabdomyoma causing chylopericardium and right-sided congestive heart failure in a dog.

A six-year-old Staffordshire bull terrier had a four-week history of progressive lethargy, ascites and exercise intolerance. A mass 3 cm in diameter obliterating the right atrial lumen was detected by echocardiographic examination. There were lactescent pericardial and serosanguineous pleural effusions. Histological and immunochemical examinations showed that the mass was a primary rhabdomyoma.

Laryngeal rhabdomyoma in a golden retriever.

A three-year-old male golden retriever had had progressive dyspnoea, exercise intolerance, stridor, and a modified bark for five months. A mass 2 cm in diameter was present dorsal to the right side of the larynx. Histological examination revealed cross-striations in some elongated cells, consistent with a diagnosis of rhabdomyoma, a diagnosis which was confirmed by positive immunohistochemical staining for myoglobin and desmin. The mass could not be removed without total laryngectomy and a permanent tracheostomy and the dog was euthanased.

The pathogenesis of so-called cardiac rhabdomyoma in swine: a histological, immunohistochemical and ultrastructural study.

To determine whether cardiac rhabdomyoma (CR) is a hamartoma of fetal cardiac myocyte, we investigated five cases of CRs that spontaneously developed in five 6-month-old hybrid swine with histological, immunohistochemical, and ultrastructural techniques. The cases were four multiple and one solitary neoplasms, which appeared as intraventricular nodules of various sizes without any congenital malformations. Histologically, the large ovoid CR cells with an occasional spiderweb appearance showed a transition from normal-looking cardiac myocytes or rarely from Purkinje cells, but no mitotic figures. Besides large amounts of glycogen, the CR cells contained many PAS-negative, large cytoplasmic vacuoles filled with eosinophilic or fibrillar substance. Immunohistochemically, the CR cells showed intense positivity for desmin and variable positivities for vimentin, alpha-atrial naturiuretic peptide, and proliferating cell nuclear antigen. These positivities were not seen in adjacent cardiac myocytes. Cytokeratin was negative in the CR cells but was positive in fetal cardiac myocytes of early gestation. Rod-like or granular positivity for alpha-actinin in the CR cells was similar to that in nemaline myopathy. Ultrastructurally, the CR cells contained myofibrils that frequently showed myofibrillar degeneration and produced large intracytoplasmic vacuoles. These myofibrils often mingled with nemaline bodies and leptofibrils that continued to the Z bands. T-systems, sarcoplasmic reticulum, and intercalated discs, which are specific features of postnatal cardiac myocytes, were sometimes observed in the CR cells. Increase of glycogen and mitochondria and appearance of atrial-specific granules associated with the Golgi apparatus were other features noted. The present findings have not been reported, even in human CR. From these new observations with the recent report on the occurrence of CR in neonatal piglets, swine CR does not belong to the entity of hamartoma but may be a congenital dysplasia of the perinatal cardiac tissues with myofibrillar degeneration, affecting mainly cardiac myocytes and rarely Purkinje cells. The various immunophenotypic changes including proliferating cell nuclear antigen and the increase and appearance of cytoplasmic elements compared with mature cardiac myocytes can be interpreted as reactive or regenerative changes due to myofibrillar degeneration.

Lingual rhabdomyoma in a dog.

A neutered male mixed breed dog, with a history of progressive dyspnoea, was presented for surgical removal of an enlarging lingual neoplasm (60 x 40 x 70 mm), previously diagnosed as a granular cell tumour. Microscopically the excised neoplasm comprised sheets of pleomorphic cells; large granular eosinophilic cells, multinucleated giant cells and smaller angular cells. A tentative diagnosis of rhabdomyoma was based on the light microscopic changes. This diagnosis was confirmed by the ultrastructural identification of bundles of intracytoplasmic filaments (interpreted to be myosin) within the neoplastic cells and the strong positive reaction of these cells to markers for "muscle-specific" actin (HHF35).

Rhabdomyoma of the ear pinna in four cats.

Four cases of rhabdomyoma of the ear pinna in white eared adult cats are reported. The lesions were raised, non-ulcerated, red-purple, discoid nodules on the convex surface of the pinna. Histologically, the nodules consisted of interlacing bundles of spindle-shaped cells that occasionally had cross striations. Lesions have not recurred 2-3 years following surgical excision. Although a specific cause for tumour development was not found, the similarity among these cases suggests that common factors played a role in the development of the lesions.

Canine laryngopharyngeal rhabdomyoma resembling an oncocytoma: light microscopic, ultrastructural and comparative studies.

A laryngopharyngeal rhabdomyoma was diagnosed in a four-year-old dog with clinical signs of upper respiratory obstruction. In people, rhabdomyomas have a predilection for the head and neck area. Features of this tumor were compared with an oncocytoma with which it may be confused.

Canine laryngeal rhabdomyoma.

Three canine laryngeal tumors were diagnosed as oncocytomas by light microscopy, but were determined to be rhabdomyomas following ultrastructural and immunocytochemical examination. Tumors consisted of large eosinophilic cells interspersed with smaller dark cells. Large tumor cells had a granular, intensely eosinophilic cytoplasm. Scattered through the tumors were a few elongated cells with cytoplasmic cross striations and multiple nuclei. Tumor cells from all three dogs contained numerous mitochondria and bundles of myofibrils with electron-dense Z-lines typical of striated muscle cells. Intracellular myoglobin and desmin were detected in the tumors by immunocytochemistry. Comparisons are made with a previous report of canine laryngeal oncocytomas.

[Pathological findings of cardiac rhabdomyomatosis in the guinea pig].

Cardiac rhabdomyomatosis of Hartley guinea pigs was examined by light and transmission electron microscopy, and its incidence and distribution were also described. Cardiac rhabdomyomatosis was found in 58 cases out of 345 animals, aged from 1.5 to 17 weeks. A few small lesions were noted in many cases, but large lesions were rare. Most lesions noted in the ventricle were found to measure from 1 mm2 to 5 mm2 in area. The larger lesions were seen near the cardiac apex. In terms of distribution of the lesions, they were observed most frequently in the left ventricular free wall. They were also distributed less frequently in the ventricular septum and in the right ventricular free wall. In bilateral free walls and the ventricular septum, this lesion was frequently noted on the endocardial side and in the tunica muscularis, respectively. Light microscopically, this lesion had a characteristic nodular-reticular structure with large vacuolated cells. Electron microscopy of cardiac rhabdomyomatosis revealed two cell types, A and B. Type A cells were characterized by large aggregates of glycogen particles distributed loosely in the cytoplasm and by myofibrils and mitochondria located at the periphery of the cytoplasm. Type B cells were characterized by large aggregates of mitochondria near the nucleus and at the periphery of the cytoplasm and by large aggregates of glycogen particles with a similar distribution to those in type in type A cells. Myocardial cells in the marginal regions of rhabdomyomatosis lesions showed mitochondrial swelling and rupture of myofibrils.(ABSTRACT TRUNCATED AT 250 WORDS)