Diagnosis and Multimodal Treatment of Metastatic Maxillofacial Juvenile Embryonal Rhabdomyosarcoma in a Young Golden Retriever.

A 2 yr old male castrated golden retriever was evaluated for a rapidly progressing maxillofacial spindle cell tumor. On examination, an ill-defined left maxillary mass, a 2 cm swelling under the left eye, and an enlarged left mandibular lymph node were noted. The dog was bright and alert but appeared painful upon jaw extension. Cytology from the lymph node revealed metastatic disease. Thoracic radiographs and computed tomography scan revealed pulmonary nodules. Computed tomography of the head and neck revealed a 6.7 × 4.1 × 6.5 cm mass at the rostral aspect of the left zygomatic arch invading the orbit. A second opinion of the biopsy specimen in conjunction with positive immunohistochemical staining for desmin led to a revised diagnosis of rhabdomyosarcoma. Treatment consisted of three doses of palliative radiation therapy, in 8 Gy fractions, and chemotherapy with vincristine, cyclophosphamide, and doxorubicin. A rapid clinical response was noted shortly after treatment initiation; however, the response was temporary, and the dog was euthanized due to widespread metastatic disease and associated clinical signs 74 days after initial therapy. This is one of the first reports describing positive results from multimodal treatment with chemotherapy and radiation therapy of a maxillofacial juvenile rhabdomyosarcoma in the veterinary literature.

Embryonal Rhabdomyosarcoma of the Oesophagus in a Young Dog.

A 15-month-old great Dane dog, showing clinical signs related to hypertrophic osteopathy, was diagnosed radiographically with a mass in the region of the thoracic oesophagus. Exploratory thoracotomy revealed an extensive, highly vascularized and locally invasive oesophageal mass and the presence of nodules in adjacent lung lobes. The dog was humanely destroyed intra-operatively. Histological examination revealed that the mass was an embryonal rhabdomyosarcoma. This is the first report of rhabdomyosarcoma of the oesophagus of a dog. Rhabdomyosarcoma should be considered a differential diagnosis when a mass adjacent to the oesophagus is diagnosed.

[Congenital embryonal rhabdomyosarcoma of the head in a red and white German Holstein calf]. / Kongenitales embryonales Rhabdomyosarkom am Kopf eines rotbunten Deutsche-Holstein-Kalbes.

Tumours with skeletal-muscle differentiation are rare in companion animals. They are differentiated into benign rhabdomyomas and malignant rhabdomyosarcomas. A female German Holstein calf displayed a congenital, spherical, subcutaneous mass at the lateral side of the head. Histology revealed an encapsulated, expansile, highly cellular mass consisting of a reticular meshwork of moderately pleomorphic, small spindle-shaped to round cells within a fibrovascular to myxoid stroma as well as multifocal, large, blunt, multinucleated myotube-like cells (strap cells). Electron microscopy demonstrated characteristic cytoplasmic bundles of myofilaments and Z-stripes within the strap cells. Immunoreactivity for vimentin was observed in the small spindle-shaped cells and for desmin in the strap cells. The results are consistent with the spectrum of findings characteristic for a bovine congenital embryonal rhabdomyosarcoma.

Orbital embryonal rhabdomyosarcoma with metastasis in a young dog.

A 2-year-old male Welsh corgi dog was brought to an animal hospital because of left upper eyelid enlargement with lachrymal gland protrusion. The lachrymal and orbital cavity mass was removed surgically. Microscopically, the orbital mass consisted of a mixture of large rhabdomyoblastic and small round tumour cells. Immunohistochemically, the rhabdomyoblastic cells expressed desmin and myoglobin and the small round cells expressed desmin, myogenin and MyoD1. A diagnosis of embryonal rhabdomyosarcoma (ERS) was made. One month later, multiple masses throughout the body were identified, in particular around the cervical region. One of these lesions was sampled and diagnosed as metastatic ERS. The dog died 84 days after the time of first admission.

Rhabdomyosarcoma in 8 horses.

This multi-institutional report describes 8 cases of rhabdomyosarcoma in horses. Four neoplasms were in the tongue and other areas of the mouth or head, 2 were in the abdominal wall, and 1 each was in right shoulder muscles and heart. Four rhabdomyosarcomas that were less than 10 cm in diameter were treated by surgical excision or radiation with no recurrence. Two neoplasms greater than 10 cm in diameter in the abdominal wall and the right shoulder were considered inoperable and led to decisions to euthanize the horses. Two neoplasms were incidental findings at necropsy. All the neoplasms were classified as embryonal except for 1 pleomorphic rhabdomyosarcoma. These 8 cases were evaluated with 9 published case reports of equine rhabdomyosarcoma. For all cases, the most common sites were limb muscles (5/17) and tongue (4/17). Metastasis was reported in 4 of the previously published cases; none was found in this study.

Subcutaneous embryonal rhabdomyosarcoma in a dog: cytologic, immunocytochemical, histologic, and ultrastructural features.

A subcutaneous mass on the left antebrachium of an 11-year-old intact female English Pointer dog was evaluated presurgically by cytologic examination and immunocytochemical staining. The sample consisted of discrete, variably sized, markedly pleomorphic neoplastic cells that expressed vimentin with diffuse cytoplasmic staining, desmin with focal paranuclear staining, and myoglobin with diffuse cytoplasmic staining, consistent with a diagnosis of rhabdomyosarcoma. Lymphocytic and histiocytic markers were negative. Aspirates of the enlarged ipsilateral prescapular lymph node were positive for metastatic disease. Surgical excision of the tumor and lymph node were followed by histologic and electron microscopic examination. Histomorphologic appearance of neoplastic cells from the mass and the lymph node paralleled cytologic findings; the histologic diagnosis was round cell variant of embryonal rhabdomyosarcoma. By ultrastructural evaluation, cells contained numerous mitochondria and masses of cytoplasmic tangled myofilaments, features typical of rhabdomyoblasts. The dog received doxorubicin (30 mg/m(2) ) every 3 weeks for 5 treatments. Local recurrence developed 6 months after resection but was not treated. Despite a guarded prognosis and untreated local recurrence, the dog was still alive 18 months after surgery. Cytologic evaluation and immunocytochemical staining were pivotal for the presurgical diagnosis of rhabdomyosarcoma.

Aggressive spindle cell rhabdomyosarcoma in an 11-month-old boxer dog.

Rhabdomyosarcoma (RMS) is a malignant neoplasm derived from mesenchymal tissue with a tendency toward myogenic differentiation associated with the embryogenesis of skeletal muscle. According to the histological features, it can be classified in embryonal, botryoid, alveolar, and pleomorphic, which usually correspond to clinical behavior and prognosis. The spindle cell (SCRMS) variant is a rare subtype of the embryonal RMS and is considered to be less aggressive lesion. The aim of the present paper is to report an unusual case of SCRMS in an 11-month-old male boxer dog diagnosed as extensive SCRMS that affected the frontal region of the skull. Due to the aggressive nature of the lesion and poor clinical prognosis the dog's owners preferred euthanasia as a treatment. A full postmortem examination was carried out. Microscopically, the lesion was composed of a highly cellular proliferation of spindle cells arranged in long and intersecting fascicles. After performing the immunohistochemical studies (HHF-35, smooth muscle actin, desmin and MyoD1), the present case was diagnosed as SCRMS.

Embryonal rhabdomyosarcoma in a Rothschild's giraffe (Giraffa camelopardalis rothschildi).

Abstract: A 3-yr-old male Rothschild's giraffe (Giraffa camelopardalis rothschildi) presented for acute swelling caudomedial to the left parietal horn. Following initial diagnostics and supportive treatment, the mass was surgically resected and intralesional chemotherapy was administered. Despite treatment, the giraffe's condition worsened and euthanasia was performed. Gross necropsy revealed neoplastic invasion and destruction of underlying parietal bone, adjacent horn base, and sinuses, and metastases in the tracheobronchial and mandibular lymph nodes and lung. Histologically, the tumor was composed of packets of anaplastic round cells. Immunohistochemical studies further characterized the tumor as an embryonal rhabdomyosarcoma. This is the first reported case of rhabdomyosarcoma in a giraffe.

Embryonal rhabdomyosarcoma in a young Maine coon cat.

Embryonal rhabdomyosarcomas are uncommon tumors in all domestic species, especially cats. A 14-month-old Maine coon was diagnosed with an embryonal rhabdomyosarcoma in the rectus abdominus muscle, which was treated with complete surgical excision. Although no clinical progression was noted after surgery, the cat succumbed to pulmonary metastasis within 7 months. The histological diagnosis was embryonal rhabdomyosarcoma (myotubular subtype). This category of striated muscle tumors is thought to have a more aggressive clinical course. The rapid demise of this cat even with no clinical or histological evidence of metastasis at the time of resection may indicate that, as in human medicine, adjuvant chemotherapy should be considered in conjunction with early surgical excision in preventing disease progression.

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.

Embryonal rhabdomyosarcoma in an immature Baird's tapir (Tapirus bairdii).

An immature Baird's tapir (Tapirus bairdii) with a history of seizure-like episodes developed signs of respiratory disease. The initial clinical diagnosis was pneumonia, and antibiotic therapy was started. The animal failed to improve after 14 days of therapy and developed unilateral, bloody nasal discharge. Endoscopic examination and radiography revealed a soft tissue mass in the nasopharynx depressing the soft palate. The tapir died 32 days after initial presentation. Histologic examination of the mass demonstrated a mesenchymal tumor composed of spindle cells with elongate nuclei forming densely packed fascicles. The neoplastic spindle cells showed prominent cross-striations. Immunohistochemistry revealed the cells to be positive for desmin and myoglobin, but negative for smooth muscle actin, confirming diagnosis of rhabdomyosarcoma. Embryonal rhabdomyosarcoma is the most common nasopharyngeal soft tissue tumor of humans, and it has been reported infrequently in dogs, horses, and pigs. Neoplasia should be a differential diagnosis in cases of unilateral nasal discharge and inspiratory stridor, even in young animals.

Juvenile parameningeal rhabdomyosarcoma in a dog causing unilateral denervation atrophy of masticatory muscles.

A 23-month-old, male, Labrador retriever dog with a history of slowly progressive right-sided atrophy of the masticatory muscles was submitted for necropsy. A highly invasive neoplasm which destroyed adjacent soft tissues including the right trigeminal nerve was found in the right side of the cranial cavity. Metastases to the liver were also present. Microscopical features of the neoplasm were compatible with those of rhabdomyosarcoma, embryonal type. This diagnosis was confirmed by immunohistochemical demonstration of desmin and muscle actin within tumour cells. In human patients, rhabdomyosarcoma is the most common soft tissue sarcoma of childhood and adolescence. Parameningeal rhabdomyosarcomas are well-known topographic variants that are often non-amenable to complete surgical resection and therefore carry a more guarded prognosis. Juvenile parameningeal rhabdomyosarcoma resulting in denervation atrophy of the muscles of mastication has not been reported previously in dogs. Rhabdomyosarcoma should be included in the differential diagnosis of neoplastic conditions in the head and neck region of juvenile dogs presented with cranial nerve palsies or other neurological deficits suggestive of meningeal or central nervous system invasion.

Differentiated embryonal rhabdomyosarcoma in a cow.

An embryonal rhabdomyosarcoma was found in the pleura of a 2-year-old Holstein cow after first delivery. The most predominant cells in the tumor were relatively small in size, but considerable numbers of more differentiated cells of larger sizes mingled with the small cells. The most differentiated cells were characterized by multinucleation, abundant cytoplasm containing cross-striated fibrils, intense immunoreactivity for desmin, and weak or negative reactivity for vimentin. Such cells, lacking mitotic activity and displaying weak or no reactivity for proliferating cell nuclear antigen, were considered to be malignant counterparts of myotubes or muscle fibers. This neoplasm seems to follow normal skeletal muscle embryogenesis, and to be capable of differentiation into the final stage of muscle development.

[Embryonal rhabdomyosarcoma in a lamb of the Texel breed]. / Ein embryonales Rhabdomyosarkom bei einem Texelschaflamm.

The subject presented here is a hitherto undescribed case of embryonic rhabdomyosarcoma found in one particular lamb. The neoplasm was localized in the left hemisphere of the head and exited in the regio supraorbitalis. After anatomical and histopathological examination of the tumor, together with immunochemistry tests, an embryonic rhabdomyosarcoma could be positively diagnosed. This is the main type of tumor that occurs in the soft tissue of children, but its appearance in other species has until now not been extensively documented.

Peripheral neuroblastoma in a young Beagle dog.

A peripheral neuroblastoma was found in the abdominal cavity of a young male beagle dog. The large tumor mass involved the left kidney and both adrenal glands. Histologically, a major portion of the neoplasm consisted of lobulated sheets of small round cells with hyperchromatic nuclei mixed with polygonal cells and neuropil. Small clusters of polygonal cells with abundant eosinophilic cytoplasm and a trabecular growth pattern were observed adjacent to some of the tumor lobules. Small, round neoplastic cells metastasized to lumbar lymph nodes and also to the adrenal glands. The neoplastic cells were positive for neuron-specific enolase, synaptophysin, and neurofilament protein. Electron micrographs revealed intracytoplasmic dense core granules, microtubules, intermediate filaments, and desmosomes in the cytoplasm of the neoplastic cells.

Urinary bladder rhabdomyosarcoma (sarcoma botryoides) in a young Newfoundland dog.

A 13-month-old female Newfoundland dog suffered from urinary bladder tumor. Histologically the tumor consisted of round or fusiform cells, occasionally having eosinophilic cytoplasms. Apparent mature rhabdomyoblasts possessing elongated eosinophilic cytoplasm and cross striations were infrequently observed. The tumor cells exhibited immuno-positive for anti-myoglobin, desmin and vimentin antibodies. Ultrastructurally, tumor cells have abundant myofibrils in their cytoplasm and Z bands were also detected. The present tumor was diagnosed as a urinary bladder rhabdomyosarcoma in a Newfoundland dog, which has not been frequently reported in dogs.

Botryoid-type embryonal rhabdomyosarcoma of liver in a young cat.

An unusual malignant mesenchymal tumor arising in the liver of a 2-year-old cat is described. Histologically, the tumor showed considerable variation in growth pattern, cellularity, and cell types. Phenotypical diversity was confirmed by immunohistochemistry, showing expression of desmin, vimentin, S-100, and neuron-specific enolase in various areas of the tumor. On the basis of histopathology, immunohistochemistry, electron microscopy, and gross morphology, the tumor was classified as botryoid-type embryonal rhabdomyosarcoma. Differential diagnosis included so-called undifferentiated (embryonal) sarcoma of the liver, a rare tumor of the pediatric age group in humans. Problems of tumor heterogeneity and differentiation in mesenchymal tumors are discussed.