Computed tomography angiography features of a retroperitoneal extra-adrenal paraganglioma in a cat.

A 7-year-old spayed female domestic shorthair cat was presented for evaluation of a large-volume abdominal space-occupying lesion. A computed tomography angiography examination detected a round retroperitoneal mass, in contact with the large abdominal vessels, characterized by an external hyperattenuating capsule and a larger hypoattenuating center. The capsule was soft-tissue attenuating with marked heterogenous contrast enhancement. The center was hypoattenuating pre- and post-contrast administration. The mass displaced both kidneys laterally and the descendent colon ventrally. The mesenteric veins and both phrenicoabdominal veins were markedly increased in diameter. However, the adrenals were not involved. On the excretory phase, no contrast enhancement was observed in either ureter, except for the proximal tract of the right ureter. At laparotomy, both ureters entered the mass that was adherent to the great abdominal vessels. The cytological diagnosis was retroperitoneal extra-adrenal paraganglioma. In cats, retroperitoneal extra-adrenal paragangliomas are very rare. This is the first computed tomography angiography report of a retroperitoneal extra-adrenal paraganglioma in a domestic cat. Key clinical message: This report describes the computed tomography angiography features of a rare case of a retroperitoneal extra-adrenal paraganglioma in a cat. These features could be taken into consideration to direct the diagnosis of a possible neuroendocrine origin for a retroperitoneal mass in a cat.

Caractéristiques de l'angiographie par tomodensitométrie d'un para-gangliome extra-surrénalien rétropéritonéal chez un chatUne chatte domestique à poils courts, âgée de 7 ans, stérilisée, a été présentée pour évaluation d'une lésion abdominale de grand volume occupant de l'espace. Un examen d'angiographie tomodensitométrique a détecté une masse rétropéritonéale ronde, en contact avec les gros vaisseaux abdominaux, caractérisée par une capsule externe hyper-atténuante et un centre hypo-atténuant plus large. La capsule présentait une atténuation des tissus mous avec une prise de contraste hétérogène marquée. Le centre était hypoatténuant avant et après l'administration le milieu de contraste. La masse a déplacé latéralement les deux reins et ventralement le côlon descendant. Le diamètre des veines mésentériques et des deux veines phrénico-abdominales était nettement augmenté. Cependant, les surrénales n'étaient pas impliquées. À la phase excrétrice, aucune augmentation de contraste n'a été observée dans les deux uretères, à l'exception du tractus proximal de l'uretère droit. Lors de la laparotomie, les deux uretères pénétraient dans la masse adhérente aux gros vaisseaux abdominaux. Le diagnostic cytologique était un paragangliome extra-surrénalien rétropéritonéal. Chez le chat, les para-gangliomes extra-surrénaliens rétropéritonéaux sont très rares. Il s'agit du premier rapport d'angiographie par tomodensitométrie d'un para-gangliome extra-surrénalien rétropéritonéal chez un chat domestique.Message clinique clé:Ce rapport décrit les caractéristiques de l'angiographie par tomodensitométrie d'un cas rare de paragangliome extra-surrénalien rétropéritonéal chez un chat. Ces caractéristiques pourraient être prises en considération pour orienter le diagnostic d'une éventuelle origine neuroendocrinienne d'une masse rétropéritonéale chez un chat.(Traduit par Dr Serge Messier).

Incidentally detected retroperitoneal paraganglioma in a 10-year-old French bulldog.

This article reports a case of a 10-year-old French bulldog initially seen for reluctance to move and episodes of pain. A magnetic resonance imaging study was undertaken in order to rule out a herniated disc. A large, retroperitoneal mass was visualized and cytological analysis suggested a neoplastic proliferation. The mass appeared to compress the caudal vena cava when viewed by abdominal CT scan. The mass was surgically removed. A nephrectomy was also carried out and aortic bleeding identified after dissection of adhesions. Despite these complications, the dog did well after the procedures. Postoperative checkups were normal. Histological and immunohistochemical analyses of the mass were compatible with a retroperitoneal paraganglioma. Key clinical message: This type of tumor is poorly described in the veterinary literature. As the behavior of this tumor type is not yet fully understood, each new description adds to our knowledge and should help in diagnosing and treating it more effectively in the future.

Paragangliome rétropéritonéal de découverte fortuite chez un bouledogue Français de 10 ans. Cet article expose le cas d'un chien mâle entier bouledogue Français de 10 ans présenté initialement pour des difficultés locomotrices et des manifestations algiques. Un examen d'imagerie par résonnance magnétique (IRM) est rapidement réalisé afin d'explorer l'hypothèse d'une hernie discale. Une volumineuse masse rétropéritonéale est alors mise en évidence. L'analyse cytologique de cette dernière est compatible avec un processus néoplasique. Après la réalisation d'un examen par tomodensitométrie de l'abdomen et la mise en évidence d'une compression marquée de la veine cave caudale par la masse, une prise en charge chirurgicale avec exérèse de la masse est décidée. Lors de l'intervention chirurgicale une néphrectomie est réalisée et un saignement aortique est identifié après la dissection des adhérences. Malgré ces complications, le chien se réveille bien et les contrôles post opératoires effectués sont satisfaisants. Les analyses histologiques et immunohistochimiques de la masse seront en faveur d'un paragangliome rétropéritonéal extra surrénalien.Message clinique clé :Ce type tumoral fait l'objet de peu de descriptions dans la littérature vétérinaire. Toute la lumière n'a pas encore été faite sur son comportement et chaque nouvelle description permet d'en enrichir les connaissances et donc de mieux comprendre ce type tumoral, ce qui, à l'avenir, pourra aider à le diagnostiquer plus facilement et à le traiter plus efficacement.(Traduit par les auteurs).

Spontaneous retroperitoneal liposarcoma in a free-ranging juvenile golden-headed lion tamarin (Leontopithecus chrysomelas).

Malignant adipocytic neoplasia is rare among nonhuman primates. We report the gross and microscopic features of a retroperitoneal liposarcoma with myxofibrosarcoma-like dedifferentiation in a free-ranging juvenile golden-headed lion tamarin (Leontopithecus chrysomelas). To our knowledge, this is the first report of such tumor subtype in New World primates.

Prognostic value of tumour-related factors associated with canine retroperitoneal hemangiosarcoma in comparison with other anatomic presentations: A retrospective observational study.

BACKGROUND: Dogs with retroperitoneal hemangiosarcoma (HSA) exhibit variable postoperative median survival times (MST). OBJECTIVE: To retrospectively evaluate the prognostic value of selected tumour-related factors, such as tumour size, rupture, invasion into adjacent tissue, involvement of lymph node and distant metastasis, they were analysed in dogs with retroperitoneal HSA. METHODS: Ten dogs with retroperitoneal HSA managed solely with surgical excision were reviewed and compared with spleen (71) and liver (9) HSA. The Kaplan-Meier method and log-rank analysis were used compare MSTs between factors. Multivariable Cox proportional-hazard analysis was used to compare differences between arising sites. RESULTS: Retroperitoneal HSA showed comparatively longer postoperative MST compared with that of spleen and liver HSA and demonstrated significantly longer MST (p = 0.003) for tumours ≥5 cm (195 days) than <5 cm (70 days). Spleen HSA revealed significantly shorter MSTs in involvement of distant lymph nodes (23 days) and distant metastasis (39 days) than those in negative (83 days, p = 0.002 and 110 days, p < 0.001, respectively). Liver HSA also revealed significantly shorter MST (16.5 days compared with 98 days, p = 0.003) for distant metastasis. Additionally, hazard ratios (HRs) and their forest plot for overall HSA revealed as poor prognostic factors, arising sites (spleen; HR 2.78, p = 0.016 and liver; HR 3.62, p = 0.019), involvement of distant lymph nodes (HR 2.43, p = 0.014), and distant metastasis (HR 2.86, p < 0.001), and as better prognostic factor of tumour size ≥5 cm (HR 0.53, p = 0.037). CONCLUSION: In combination with overall HSA, retroperitoneal HSA shows comparatively longer postoperative MST compared to spleen and liver HSA, associated with tumour size ≥5 cm suggesting better prognostic factor.

Treatment of retroperitoneal sarcoma results in improved outcomes.

OBJECTIVE: To report the clinical characteristics, treatments, and outcomes in a cohort of dogs with histologically confirmed retroperitoneal sarcoma (RPS) and to identify potential variables of prognostic significance. ANIMALS: 46 client-owned dogs from 10 clinics with histopathologic diagnosis of a sarcoma originating from the retroperitoneal space. METHODS: Medical records were retrospectively reviewed to obtain information regarding clinical characteristics, treatments, and outcomes. Recorded variables were analyzed to report descriptive data for all cases and overall survival time. Multivariate analysis was utilized to evaluate prognostic factors for overall survival. RESULTS: Hemangiosarcoma was the most common histologic subtype diagnosed (76.1%). Cytoreductive and curative intent surgical excision of the RPS was attempted in 12 and 22 dogs, respectively; 12 dogs underwent no surgery or had an exploratory laparotomy with incisional biopsy only. Nineteen dogs received adjuvant chemotherapy, either injectable or metronomic, and 1 dog received adjuvant radiation therapy. Fourteen of the 34 (41.2%) surgically treated dogs developed evidence of local recurrence, but there was no difference in local recurrence when comparing dogs categorized as curative intent versus cytoreductive surgery. The median overall survival time was 238 days. On multivariable analysis, treatment approach was associated with survival with surgical excision (vs palliative treatment) and adjuvant chemotherapy following surgery being protective against death. A diagnosis of hemangiosarcoma was associated with a greater hazard of death. CLINICAL RELEVANCE: This study demonstrates a substantially greater survival time than previously published and suggests a survival benefit from surgical excision and adjuvant chemotherapy.

Retroperitoneal hemangiosarcoma in a common carp Cyprinus carpio: a case report.

A 7.5 kg common carp Cyprinus carpio presented with prominent localized swelling in the caudal right coelomic area, identified by ultrasound as a fluid filled mass. Fine needle aspirate (FNA) and culture results suggested a sterile seroma. Centesis removed 290 ml of serosanguinous fluid that returned within days. Recheck ultrasonography revealed a solid component within the cavity. Radiography demonstrated irregular lysis and misalignment of vertebrae adjacent to the mass, most suggestive of bacterial osteitis or neoplasia. Treatment with antibiotics followed for 2 mo but failed to resolve the lesion. Repeated radiography and ultrasonography showed progressive enlargement of the mass, with vertebral lysis and invasion characteristic of neoplasia. Ultrasound-guided FNA of the solid component of the mass was non-diagnostic. Euthanasia was elected due to the poor clinical response and primary differential of neoplasia. Post-mortem MRI and CT confirmed a retroperitoneal soft tissue mass, partially surrounded by a fluid-filled cavity, causing vertebral lysis and infiltration of the spinal canal. Expansion of the mass caused severe muscle loss and an associated elevation in creatine kinase (>120000 U l-1). Necropsy results corroborated the MRI and CT findings, revealing a retroperitoneal, multilobular, red and tan mass causing dorsal displacement of the vertebral column, with vertebral lysis, pathologic fracture and invasion of the spinal canal. Histopathologic examination revealed a locally aggressive neoplasm exhibiting multiple patterns of growth, including endothelial lined vascular channels and solid areas formed by more pleomorphic polygonal and spindle cells, consistent with hemangiosarcoma.

Laparoscopic resection of retroperitoneal paraganglioma close to caudal vena cava in a dog.

OBJECTIVE: To report laparoscopic resection of retroperitoneal paraganglioma close to the caudal vena cava in a dog. STUDY DESIGN: Case report. ANIMAL: Twelve-year-old, neutered male Jack Russell terrier. METHODS: The dog had undergone three previous cystotomies for bladder stones. On follow-up ultrasonographic evaluation, a 14-mm × 17-mm tumour was incidentally detected in the dorsal midline of the caudal abdomen. The dog underwent computed tomography (CT) imaging and ultrasound-guided fine needle aspiration of the tumour under general anaesthesia. CT imaging showed that the tumour was close to the caudal vena cava. There was no evidence of metastasis. Neuroendocrine tumour was suspected on cytologic examination. Based on these findings, laparoscopic tumour resection was performed using a vessel-sealing device. The operation time was 136 minutes. RESULTS: The dog was stable after recovery from anaesthesia and discharged to home the next day. Histopathological diagnosis of the tumour was a paraganglioma. The dog remained without clinical evidence of recurrent tumour or metastasis for 670 days after the surgery. CONCLUSION: Retroperitoneal paraganglioma in dogs is uncommon, but it is one of the differential diagnoses of a retroperitoneal tumour. Laparoscopic resection of a retroperitoneal paraganglioma was successfully performed in the dog. Laparoscopic resection conferred the advantages over open surgery of being minimally invasive, providing better visualization of the surgical field through pneumoperitoneum and semisternal patient recumbency, and allowing for magnification of the operative field, which facilitated the ease and safety of the procedure.

Retroperitoneal lymphatic malformation in a dog.

BACKGROUND: Lymphatic vascular malformations are rare findings in canine patients with six reports available in veterinary literature. Retroperitoneal cystic lymphatic malformations have not been described previously in canine patients and neither has the use of immunohistochemistry to determine their origin, i.e. vascular versus lymphatic. CASE PRESENTATION: An 8-year-old neutered female Cocker spaniel was referred for pollakiuria, dysuria and a painful abdomen. Computed tomography scanning of the abdomen showed a fluid filled structure adjacent to the urinary bladder. During surgical exploration, a thin walled cystic structure with sero-haemorrhagic fluid was found, extending from the retroperitoneal space into the abdomen. The mass was excised and submitted for histopathology, revealing a cystic mass lined by a fibrovascular capsule within the retroperitoneal/mesenteric adipose tissue. The inner surface of the cyst was lined by a single layer of bland, flattened spindle cells. Intramural blood vessels were well differentiated, with perivascular haemorrhage. On recurrence 11 months later, the mass was excised for the second time and a PleuralPort (Norfolk Animal products) was placed. Fifteen months after initial presentation, progression occurred with haemorrhagic fluid in the cystic space, pleural- and abdominal cavities and the owners opted for euthanasia. Histopathology and positive immunohistochemistry for lymphatic markers lymphatic vessel endothelial hyaluronic acid receptor-1 (LYVE-1) and prospero homeobox protein-1 (PROX-1) confirmed a lymphatic vascular origin of the cystic structure. CONCLUSIONS: To our experience, a definitive diagnosis of retroperitoneal cystic malformation of lymphatic origin could be done only by combining the clinical presentation, advanced imaging, histopathology and LYVE-1 and PROX-1 immunohistochemistry. This is the first report of a vascular malformation in a dog where immunohistochemistry was used to make a final diagnosis. A lymphatic malformation, even if rare, should be added on the list of the differential diagnosis in a patient with a retroperitoneal cystic structure containing serohaemorrhagic fluid. Results of this case report can aid in diagnosis of future cases, however, further studies on therapy and management are needed to provide additional information about optimal treatment of these patients.

Characterization of exogenous type D retrovirus from a fibroma of a macaque with simian AIDS and fibromatosis.

A novel type D retrovirus was isolated by cocultivation of explants of fibromatous tissue from a rhesus monkey (Macaca mulatta) with immunodeficiency and retroperitoneal fibromatosis. This type D virus, isolated from a macaque with simian acquired immunodeficiency syndrome (SAIDS-D/Washington), is exogenous and is partially related to the Mason-Pfizer and the langur monkey type D viruses. The SAiDS-D virus can be distinguished from all other primate retroviruses by antigenicity and molecular hybridization. Nucleic acid hybridization studies reveal that the origin of the SAIDS-D isolate may reside in Old World monkey (subfamily Colobinae) cellular DNA.

Retroperitoneal teratoma in a domestic rabbit (Oryctolagus cuniculus).

Teratomas are histologically complex tumors arising from germ cells of two or three embryonic layers either in the gonads or occasionally from germ cells that mistakenly migrated to ectopic sites. A case of retroperitoneal teratoma in a regularly slaughtered 4-month-old, male domestic rabbit is reported. A pale reddish, 3 x 4 cm, fibrous mass was detected, loosely connected to the parietal wall in the retroperitoneal region cranial to the kidney. Histologically, the neoplasm contained tissues from ectodermal, endodermal and mesodermal germ layers: nerves and neurons simulating ganglia, cysts lined by squamous epithelium containing keratin and hair, skin adnexa; respiratory glandular epithelium, serous and salivary glands; collagenous connective tissue, muscle fibers, mature cartilage and bone, bone marrow, teeth and fat. To the authors' knowledge this is the first report of a retroperitoneal teratoma in the rabbit.

Metastatic myxosarcoma in a Quarter Horse gelding.

A 22-y-old Quarter Horse gelding was presented to the University of Illinois Veterinary Teaching Hospital for evaluation of increased heart rate and mild colic signs. Rectal examination revealed a large left perirenal mass. Abdominal ultrasonography further confirmed this finding. Thoracic ultrasonography indicated multifocal irregularities on the pleural surface suggestive of consolidation and possibly masses in the lungs. The animal was euthanized. Autopsy findings included a large, firm, expansile, gelatinous retroperitoneal mass that surrounded both kidneys, as well as nodules with similar morphology in the lungs, liver, intestinal mesentery, cecum, and caudal mesenteric artery. Histologically, the masses were composed of neoplastic stellate-to-spindloid cells in abundant mucinous stroma. Neoplastic cells exhibited strong immunoreactivity for vimentin and were negative for pancytokeratin (A1/A3), CD3, CD20, melan A, and synaptophysin. Mucinous stroma was strongly positive with alcian blue and weakly positive with periodic acid-Schiff histochemical staining. These findings are consistent with metastatic myxosarcoma. Myxosarcoma is a rare neoplasm in horses, and metastasis to tissues other than sentinel lymph nodes has not been described previously to our knowledge.

Subcutaneous ureteral bypass for treatment of bilateral ureteral obstruction in a cat with retroperitoneal paraganglioma.

CASE DESCRIPTION A 7-year-old female domestic shorthair cat was referred for evaluation of azotemia and unilateral hydronephrosis. CLINICAL FINDINGS Abdominal ultrasonography revealed right-sided hydronephrosis and dilation of the proximal aspect of the ureter; the left kidney was small with irregular margins. A highly vascular, irregular retroperitoneal mass, not clearly associated with the ureteral obstruction, was also visualized. Surgical exploration confirmed a retroperitoneal mass involving the caudal mesenteric artery and both ureters, with hydroureter on the right side. TREATMENT AND OUTCOME A subcutaneous ureteral bypass (SUB) device was surgically implanted to treat right ureteral obstruction, and the mass was biopsied. Shortly after surgery, progressive azotemia and hyperkalemia were detected; ultrasonographic examination revealed left-sided hydronephrosis and hydroureter, which was suspected secondary to inflammation of the mass causing a left-sided ureteral obstruction. A second surgery was performed to place an SUB device for the left kidney and remove the retroperitoneal mass; both ureters were ligated at the mid- and distal aspects and then transected and removed with the mass. A neuroendocrine paraganglioma was identified by histopathologic evaluation of the mass. Hydronephrosis improved (right kidney) or resolved (left kidney) after surgery, and azotemia improved. Chemotherapeutic intervention was declined. Markers of renal function were static during the 14-month follow-up period. At the last follow-up evaluation, the patient was reportedly doing well, and both SUB devices were patent. CLINICAL RELEVANCE This was the first report of retroperitoneal paraganglioma in a domestic cat causing bilateral ureteral obstruction. Bilateral SUB device placement enabled en bloc mass resection and provided long-term relief of ureteral obstruction.

Retroperitoneal hemangiosarcoma causing chronic hindlimb lameness in a dog.

The clinical, radiographic, ultrasonographic, computed tomographic, surgical and histopathological findings in a Boxer dog with retroperitoneal hemangiosarcoma are described in this study. A seven-year-old, male, castrated Boxer dog was referred for evaluation of chronic hindlimb lameness. The physical examination revealed muscle atrophy and sciatic nerve deficits. Radiography and ultrasonography revealed a caudodorsal abdominal mass. Computed tomography revealed that the mass involved the left margin of the L7 vertebra, lumbosacral canal, and lumbosacral plexus. At surgery, a large retroperitoneal haematoma was removed. Histopathology of amorphous tissue found near the haematoma was consistent with haemangiosarcoma. The owner declined any further treatment. Ten weeks after discharge, the dog was euthanatized due to collapse and haemo-abdomen.

Congenital infiltrative lipomas and retroperitoneal perirenal lipomas in a calf.

BACKGROUND: Congenital lipocytic tumours have rarely been reported in cattle. Lipomas are benign tumours, but infiltrative lipomas have significant health implications due to their aggressive infiltrative growth pattern. CASE PRESENTATION: A calf was born with skeletal malformations and soft tissue proliferations, primarily on the external thoracic wall. The calf was euthanized for welfare reasons and submitted for post mortem examination. Necropsy, histopathology and post mortem computed tomography scanning revealed two types of lipocytic tumours. Widespread infiltrative lipomas were present in the muscles and connective tissues along the vertebral column and diffusely invaded the external soft tissues of the right thoracic wall. The neoplastic lipocytes had invaded intervertebral spaces thus causing congenital vertebral malformations, and further invaded the vertebral canal and the bone marrow of coccygeal vertebrae. Periosteal localization of the tumour was associated with costal hyperostosis. Two large retroperitoneal lipomas enclosed the kidneys and occupied much of the abdominal space. CONCLUSION: The development of congenital bone malformation in this calf illustrates the severe consequences of the infiltrative and aggressive growth of infiltrative lipomas during foetal development. The congenital retroperitoneal lipomas occupied a large part of abdominal cavity, but did not invade the adjacent tissues. Due to their large size, perirenal lipomas should be considered in calves with distended abdomen, even in cases without other signs of tumours.

Retroperitoneal extraskeletal mesenchymal chondrosarcoma in a dog.

A young adult female Mastiff dog developed a large retroperitoneal mass, pleural effusion, and multiple pulmonary and pleural nodules. All masses were diagnosed as mesenchymal subtype chondrosarcomas, using histological and immunohistochemical criteria. Reports of canine extraskeletal mesenchymal chondrosarcomas (EMCs) are rare but involved animals less than 3 years of age in 60% of the cases. This is the first description of this type of tumor developing distant metastases. Evidence from this case and previous reports suggests that EMCs are associated with a poor prognosis.

Teratoma in a chicken (Gallus domesticus).

A large mass composed of multiple tissue elements was observed in the abdominal cavity of a chicken. The tumor mass was tridermic microscopically, and therefore classified as a teratoma.

Malignant retroperitoneal paraganglioma in a horse.

A large primary retroperitoneal sublumbar neoplasm in a horse, with disseminated neoplastic foci in the brain, lung, kidney and spleen is described. The diagnosis was based on light microscopical studies and positive immunostaining for neuron-specific enolase. Because of the location of the primary tumour mass, the aortico-sympathetic ganglion (organ of Zukerkandl) is proposed as the origin.

Malignant retroperitoneal paraganglial tumour in a cow.

A large primary retroperitoneal sublumbar neoplasm was identified in an 11-year-old Holstein cow, with metastases to the lungs, kidneys and lymph nodes. The tumour cells proliferated in a characteristic endocrine pattern, were argyrophilic and positive for neuron-specific enolase, and had membrane-bounded intracytoplasmic granules. In addition, the cells were occasionally positive for cytokeratin and had desmosome-like intercellular junctions. The primary tumour mass was diagnosed as a malignant paraganglial tumour of the aortico-sympathetic ganglion (organ of Zuckerkandl), and was considered to contain primitive cells with epithelial differentiation.

Caprine peripheral neuroblastomas: structural and ultrastructural features, intermediate filaments profile and neuro-endocrine characterization.

In this report the morphological and immunohistochemical features with respect to intermediate filament proteins and the neuroendocrine nature of bilateral neuroblastomas possibly originating from the adrenal medulla in a goat kid are presented. Histologically, the tumours were composed of small, round, blue cells organized in highly cellular nests and sheets separated by fibrovascular septa. Isolated cells mimicking the morphological features of neurones were observed in both tumours. Ultrastructurally, dense-core neurosecretory granules, about 100 nm in diameter, and irregularly organized neurotubular networks were seen. The small tumour cells were only labelled by vimentin, while the neurone-like cells were labelled by both neurone-specific enolase and synaptophysin. The lack of staining of the tumour cells by the neurofilament proteins antiserum, which was also observed in a human neuroblastoma (used as positive control) has been previously reported and is probably the result of the tissue processing and/or the poor differentiation stage of the tumours. The vimentin labelling of tumour cells could be explained by the poor differentiation stage of the tumours, since vimentin is the only intermediate filament protein in presumptive neuroblasts, being replaced by neurofilament proteins in later stages of neurogenesis.

Canine hemangiosarcoma treated with standard chemotherapy and minocycline.

Standard treatments for canine hemangiosarcoma include surgery and chemotherapy with doxorubicin, but in spite of treatment most dogs with this disease die within 6 months of diagnosis. Tumor growth and metastasis are angiogenesis dependent. Antiangiogenic drugs such as minocycline may provide therapeutic benefits in cancer patients. The purpose of this prospective study was to evaluate the efficacy of chemotherapy with doxorubicin and minocycline, an antiangiogenic agent, in dogs with hemangiosarcoma. Eighteen dogs with histologically confirmed hemangiosarcoma of any stage were treated with doxorubicin, cyclophosphamide, and minocycline. Complete staging was performed before and during the treatment period to assess remission status and response to therapy. No statistically significant difference was found in survival between the dogs treated with chemotherapy and minocycline, and historical controls consisting of dogs that received chemotherapy alone. Postmortem examination revealed widespread metastasis, suggesting that minocycline is ineffective as a single antiangiogenic agent in canine hemangiosarcoma.