Genitourinary rhabdomyosarcoma with systemic metastasis in a young dog

A 2-year-old intact female Golden Retriever presented due to rapidly progressing depression, ascites, dysuria, abdominal pain, and severe vaginal bleeding. At necropsy, the retroperitoneal space was expanded by multiple coalescing neoplastic nodules and the uterine wall was thickened with poorly defined neoplastic infiltrates. The urinary bladder was markedly thickened due to botryoid nodules exhibiting exophytic growth into the lumen. Metastases to lung, liver, kidney, and abdominal and thoracic lymph nodes were also noted. Microscopically, the genital tract and retroperitoneal masses were consistent with the alveolar subtype of rhabdomysarcoma, while the urinary bladder mass had characteristics of the embryonal subtype. Immunohistochemically, the neoplastic cells in all these tissue sites were intensely positive for desmin, sacromeric actin, and vimentin, while they were uniformly negative for cytokeratin and smooth muscle actin. Phosphotungstic acid hematoxylin stain revealed cross-striations in the cytoplasm of scattered neoplastic cells. Based on the gross findings, histopathology, and immunohistochemistry, genitourinary rhabdomyosarcoma with multisystemic metastases was made.     

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.     

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

Abstract: 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/m²) 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.     

Vaginal rhabdomyosarcoma in a dog

A 10-year-old, female, mongrel showed hemorrhage from vulva. By magnetic resonance image (MRI) and endoscopic examination, a multipapillary mass with a grape-like appearance was found around the urethral opening. Histologically, the mass consisted of variable-sized round-, spindle-to-polygonal-shaped tumor cells including many multinuclear cells. Mitotic figures were also frequently observed. In some areas, that tumor cells were loosely arranged, with intercellular myxoid components. Immunohistochemically, these tumor cells were strongly positive for vimentin and focally positive for desmin but negative for myoglobin. Thus, the case was diagnosed as a relatively poorly differentiated botryoid rhabdomyosarcoma by the macroscopic, histopathologic, and immunohistochemical identification. This is the first report of botryoid rhabdomyosarcoma developing in the vagina of a dog.     

Intracardiac rhabdomyosarcoma in a dog

Intracardiac rhabdomyosarcoma was diagnosed in a 14-month-old Golden Retriever referred for evaluation of syncope. The dog was weak, with irregular heart rate, pulse deficit, heart murmur, and hepatomegaly. Thoracic radiography revealed generalized cardiomegaly, and electrocardiography revealed sinus rhythm with multiform ventricular premature complexes and intermittent ventricular tachycardia. Two-dimensional echocardiography revealed extensive soft-tissue density masses in both ventricles. An intracardiac neoplasm seen at postmortem examination was identified histologically as rhabdomyosarcoma, an uncommon intracardiac tumor in dogs.     

Perianal rhabdomyosarcoma in a dog

A perianal rhabdomyosarcoma was diagnosed in an 11-year-old neutered male Labrador retriever. Following two incomplete surgical excisions of the tumour, the dog was treated by means of surgery combined with local radiotherapy and systemic chemotherapy using one cycle of vincristine sulphate, doxorubicin and cyclophosphamide (VAC protocol). The dog died 252 days after the first combined therapy. Radiography at this time demonstrated enlargement of the iliac lymph nodes, suggesting metastasis of the tumour. To the authors' knowledge, this is the first report of treatment of canine perianal rhabdomyosarcoma.     

Lymphoma(s) showing epitheliotropism and diffuse skeletal muscle involvement presenting as a polymyopathy in a young dog

A 3-year-old dog presented with a severe polymyopathy and subsequently developed nodular skin lesions. The disease in this dog was caused by lymphoma, showing cutaneous epitheliotropism as well as infiltration of skeletal muscle in conjunction with polymyositis.     

Cervical neoplasia originating from the vagus nerve in a dog

An eight-year-old intact male Bernese mountain dog was referred with a history of chronic vomiting, coughing and signs of respiratory distress. Other historical findings included lethargy, weight loss and choking. On presentation, clinical findings were Horner's syndrome, ipsilateral laryngeal hemiplegia, coughing, gagging, respiratory distress and vomiting. Lateral cervical radiographs showed ill-defined mineralisation in the soft tissue ventral to the third cervical vertebra, while ultrasonography of the neck revealed a well marginated heterogeneous mass with focal hyperechogenic lesions and acoustic shadowing. Results of an ultrasound-guided fine needle aspirate suggested neoplasia. At necropsy, a large tumour was detected in the ventral cervical region, originating from the right vagosympathetic trunk. In view of the infiltrating pattern, the cellular pleomorphism and the numerous mitoses on histopathological examination, the tumour was classified as a malignant peripheral nerve sheath tumour.     

Aortic and iliac thrombosis associated with angiosarcoma of skeletal muscle in a dog

A seven-year-old, neutered male greyhound was presented with a history of episodic shifting hindlimb lameness and pain. Ischaemic necrosis of areas of the hindlimb digits and skin and a firm swelling within the medial right thigh musculature were found on physical examination. Investigation demonstrated thrombosis of the terminal aorta and right external iliac artery with ischaemic necrosis of muscular and dermal tissue distal to the sites of thrombosis. The dog was euthanased due to poor prognosis. Necropsy findings were of a poorly differentiated invasive sarcoma of the skeletal muscle of the proximal right hindlimb, thrombosis of the aorta and right external iliac artery and secondary renal glomerulopathy. Immunohistochemistry of the neoplastic tissue indicated angiosarcoma based on expression of CD31 and factor VIII-related antigen. Thrombosis was considered likely to be due to systemic hypercoagulability because of the presence of altered flow characteristics and endothelial damage in the vascular tumour bed. Aortoiliac thrombosis, paraparesis and hindlimb ischaemia are unusual sequelae of angiosarcoma in the dog.     

A rhabdomyosarcoma arising in the larynx of a dog

A neoplastic nodular lesion, 2 × 3 cm in diameter, was found in the larynx of a 6-year-old spayed female dog. The tumor was ill-circumscribed, consisting histologically of large round cells with abundant cytoplasm interspersed with small round cells with less cytoplasm and occasional multinucleated cells (myotubes). Immunohistochemically, tumor cells were positive for myoglobin, desmin and vimentin in varying degrees, but negative for S-100 protein, GFAP or cytokeratin. Cytoplasmic myofilaments/myofibrils with a dense Z-line-like structure were seen, the fine structures of which were complemented by PTAH stain. Based on these findings, the tumor was diagnosed as a rhabdomyosarcoma, a very rare tumor in the larynx of dogs.     

Adenocarcinoma metastasis of the intertransversarius cervicis muscle eliciting a right forelimb lameness in a dog

This article describes identification of a metastatic adenocarcinoma to the intertransversarius cervicis muscle using magnetic resonance imaging (MRI) in a dog that presented with chronic lameness of the right forelimb. Magnetic resonance imaging revealed a right sided, ovoid signal abnormality within the intertransversarius cervicis muscle lateral to the sixth cervical (C6) vertebra. The lesion was uniform, hyperintense on T2- and isointense on T1-weighted images to muscle and exhibited uniform contrast enhancement on T1-weighted images. The MRI findings were consistent with a neoplasia. Surgical excision was performed. Histopathological diagnosis was metastatic fibrous adenocarcinoma. The dog recovered rapidly but 6 months post-operatively he was killed because of lung metastases. Necropsy was declined and the primary tumour could not be identified.