Skeletal metastasis as the initial clinical manifestation of metastatic carcinoma in 19 dogs

Intensive Multimodal Chemotherapy in a Dog Suffering from Grade III/Stage IV Solid Mammary Carcinoma

Very few studies, often with very small cohorts, have proven chemotherapy efficacy against canine aggressive mammary carcinomas, either in terms of metastasis or median survival, in dogs after surgery and chemotherapy, with such outcomes not being confirmed by other studies. As a result, we lack efficient standardized protocols, which exist in human cases, according to the grade and stage of the tumor in dogs. In this case report, we describe a relapsing grade III solid mammary carcinoma evolving into prominent lymphatic intravascular invasion with multifocal nodal extension (stage IV); we applied an intensive treatment combining radical surgery and intensive adjuvant chemotherapy. The latter combined carboplatin maximal-tolerated-dose chemotherapy, with doses adjusted as necessary, and metronomic chemotherapy with firocoxib, toceranib and chloraminophene, progressively administered and carefully monitored. Adapting the doses prevented adverse events and resulted in 218 days of survival with good quality of life. To our knowledge, this is the first description of such a treatment combination. Our result should be confirmed with a large-scale prospective study.

Tissue S100/calgranulin expression and blood neutrophil-to-lymphocyte ratio (NLR) in prostatic disorders in dogs

BACKGROUND

Prostatic carcinoma (PCA) is a rare but severe condition in dogs that is similar to the androgen-independent form of PCA in men. In contrast to humans, PCA is difficult to diagnose in dogs as reliable biomarkers, available for PCA screening in human medicine, are currently lacking in small animal oncology. Calprotectin (S100A8/A9) and S100A12 are Ca2+-binding proteins of the innate immune system with promising potential to distinguish malignant from benign urogenital tract conditions, similar to the blood neutrophil-to-lymphocyte-ratio (NLR). However, both have not yet been extensively investigated in dogs with PCA. Thus, this study aimed to evaluate the expression of the S100/calgranulins (calprotectin, S100A12, and their ratio [Cal-ratio]) in prostatic biopsies from nine dogs with PCA and compare them to those in dogs with benign prostatic lesions (eight dogs with prostatitis and ten dogs with benign prostatic hyperplasia [BPH]) as well as five healthy controls. In addition, blood NLRs were investigated in twelve dogs with PCA and 22 dogs with benign prostatic conditions.

RESULTS

Tissue S100A8/A9+ cell counts did not differ significantly between tissue from PCA and prostatitis cases (P = 0.0659) but were significantly higher in dogs with prostatitis than BPH (P = 0.0013) or controls (P = 0.0033). S100A12+ cell counts were significantly lower in PCA tissues than in prostatitis tissue (P = 0.0458) but did not differ compared to BPH tissue (P = 0.6499) or tissue from controls (P = 0.0622). Cal-ratios did not differ significantly among the groups but were highest in prostatitis tissues and significantly higher in those dogs with poor prostatitis outcomes than in patients that were still alive at the end of the study (P = 0.0455). Blood NLR strongly correlated with prostatic tissue S100A8/A9+ cell counts in dogs with PCA (ρ = 0.81, P = 0.0499) but did not differ among the disease groups of dogs.

CONCLUSIONS

This study suggests that the S100/calgranulins play a role in malignant (PCA) and benign (prostatic inflammation) prostatic conditions and supports previous results in lower urinary tract conditions in dogs. These molecules might be linked to the inflammatory environment with potential effects on the inflammasome. The blood NLR does not appear to aid in distinguishing prostatic conditions in dogs. Further investigation of the S100/calgranulin pathways and their role in modulation of tumor development, progression, and metastasis in PCA is warranted.

A retrospective study on bone metastasis in dogs with advanced-stage solid cancer

OBJECTIVES

To review clinical characteristics, treatment, outcome and prognostic factors in dogs with solid cancer-bearing bone metastases.

MATERIALS AND METHODS

Records were reviewed from dogs with histologically-proven solid cancer and bone metastases. Clinicopathologic variables, bone metastases characteristics and skeletal-related events were recorded. Endpoints were time to bone metastases and survival.

RESULTS

Fifty dogs were included, 20 of them with synchronous and 30 of them with metachronous bone metastases. In the latter group, median time to diagnosis of bone metastases was 210 days (range, 30 to 1835). Most common primary cancer locations included mammary gland (n=6), spleen (n=5) and tonsil (n=5). Most common histotypes were carcinoma (n=32) and hemangiosarcoma (n=10). Nineteen dogs had multiple bones involvement, with humeri and vertebrae more commonly affected. Twenty-four dogs received antitumoural therapy, five symptomatic treatment and 21 were not treated. Overall median survival after bone metastases diagnosis was 30 days (range, 11 to 49); 83% of dogs died because of skeletal-related events. Lack of antitumoural therapy was significantly associated with shorter survival (hazard ratio: 2.7; 95% confidence interval: 1.3 to 5.6) and with increased risk of skeletal-related death (hazard ratio: 3.3; 95% confidence interval: 1.4 to 7.4). Dogs with endocrine/neuroendocrine tumours (odds ratio: 8.8; 95% confidence interval: 1.2 to 63.9), without appendicular metastases (odds ratio: 5.1; 95% confidence interval: 1.0 to 25.8), without extra-skeletal metastases (odds ratio: 5.2; 95% confidence interval: 1.1 to 24.5) and receiving antitumoural therapy (odds ratio: 14.8; 95% confidence interval: 1.7 to 131.4) had an increased chance of surviving more than 100 days.

CLINICAL SIGNIFICANCE

Bone metastases in dogs with solid cancers are associated with poor prognosis and a high risk of skeletal-related events. Treatment appears to have an impact on survival.

Surgical management of a metastatic vertebral tumour originating from a mammary adenocarcinoma in a dog

An 11-year-old spayed female Toy Poodle presented with acute tetraparesis. A small subcutaneous mass was found in the right trunk region, and the magnetic resonance revealed a compressive spinal cord lesion due to an irregular bone proliferation at the third cervical vertebra. After surgical resection of the vertebral lesion, the neurological symptoms improved, and the patient could walk on her own. The excised vertebral and subcutaneous masses were diagnosed as a mammary adenocarcinoma on the histopathological examination, with Ki-67 and HER-2 immunohistochemistry staining. This case report highlights the importance of defining the primary tumours of metastatic vertebral tumours and the necessity of palliative surgery to improve the patient's quality of life.

American Canine Hepatozoonosis Causes Multifocal Periosteal Proliferation on CT: A Case Report of 4 Dogs

American canine hepatozoonosis (ACH) represents an important but relatively uncommon differential diagnosis in a dog with fever, muscle wasting, profound leukocytosis, and/or musculoskeletal pain. Despite this, obtaining a definitive diagnosis can prove difficult. Peripheral blood smears and whole-blood polymerase chain reaction (PCR) rely on rare parasitemia, and the gold standard diagnostic test (skeletal muscle biopsy) is uncommonly pursued due to its invasive and costly nature. Demonstration of characteristic periosteal proliferative lesions aids diagnosis. The lesions typically involve the more proximal long bones of the appendicular skeleton. The periosteal proliferation is of currently unknown pathogenesis, but its distribution is characteristic of this disease with few differential diagnoses. This case series describes the findings on computed tomography (CT) in 4 dogs with PCR- or cytologically-confirmed Hepatozoon americanum. All dogs had multifocal, bilaterally asymmetric, irregularly marginated, non-destructive, non-articular, periosteal proliferative lesions. Recognition of this unusual CT finding and awareness of this disease could assist in the diagnosis and subsequent treatment of dogs with ACH and may offer an additional indication for CT in cases of fever, muscle wasting, and myalgia.

Cranial and vertebral osteosarcoma commonly has T2 signal heterogeneity, contrast enhancement, and osteolysis on MRI: A case series of 35 dogs

Magnetic resonance imaging (MRI) is commonly used to evaluate the central nervous system (CNS) in dogs; however, published studies describing the MRI appearance of cranial and vertebral osteosarcoma are scarce. In this multicenter, retrospective, case series study, MRI studies of 35 dogs with cranial or vertebral osteosarcoma were prospectively scored by consensus of two veterinary radiologists. Recorded characteristics were location, signal intensity (compared to gray matter), homogeneity, contrast enhancement, margin delineation, local invasion, osteolysis, osteosclerosis, zone of transition, periosteal proliferation, pathological fracture, meningeal/CNS involvement, and presence of metastatic disease. Locations included the parietal bone (n = 1), occipital bone (n = 2), or cervical (n = 5), thoracic (n = 17), lumbar (n = 7), or sacral vertebrae (n = 3). Common features included signal heterogeneity in T2-weighted (T2W) images (n = 35), contrast enhancement (in all 34 dogs with postcontrast MRI), osteolysis (n = 34), compression of the CNS or cauda equina (n = 33), an associated soft tissue mass (n = 33), a long zone of transition (n = 30), osteosclerosis (n = 28), signal isointensity to normal-appearing gray matter in T1-weighted images (T1W, n = 26), and T2W hyperintensity of adjacent brain or spinal cord (n = 23). Other findings included periosteal proliferation (n = 18), meningeal contrast enhancement (n = 17), T1W and T2W hypointense foci in the soft tissue mass (n = 14), invasion into adjacent bones (n = 10), pathological vertebral fractures (n = 7), regional lymphadenopathy (n = 6), skip metastases (n = 2), lung nodule (n = 1), diaphragmatic nodule (n = 1), and brain invasion (n = 1). Contrast enhancement was typically strong and heterogeneous. Magnetic resonance imaging features of cranial and vertebral osteosarcoma were analogous to those previously reported for other imaging modalities. Osteosarcoma should be a differential diagnosis for compressive, contrast-enhancing, osteolytic lesions of the cranium or vertebrae.

Low-field magnetic resonance imaging characteristics of multifocal vertebral lesions in dogs

BACKGROUND

There is a lack of information regarding magnetic resonance imaging (MRI) features of polyostotic vertebral lesions in dogs. The aim of this retrospective study was to identify and differenciate low-field MRI features of aggressive versus benign multifocal vertebral diseases in dogs.

METHODS

MRI examinations from 49 dogs with polyostotic vertebral lesions were reviewed. Images were evaluated for vertebral intensity changes, expansile lesions, new bone formation, cortical bone interruption, paravertebral musculature changes, lymphadenomegaly, spinal cord compression and spinal cord signal changes.

RESULTS

Twenty-nine dogs with non-aggressive bone lesions and 20 dogs with aggressive vertebral lesions were included. Non-aggressive lesions had variable T2-weighted fast spin-echo (T2W) signal intensity and the majority displayed low signal intensity on short tau inversion recovery (STIR). Aggressive lesions predominantly had high T2W and STIR signal intensity, with variable signal intensity on T1-weighted spin-echo and contrast enhancement. Aggressive lesions were associated with spinal pain (p < 0.01), new bone formation (p = 0.02), spinal cord compression (p < 0.01) and lymphadenomegaly (p < 0.01). Cortical interruption (p < 0.01) and paravertebral musculature changes (p < 0.01) were the strongest indicative imaging features for aggressive lesions.

CONCLUSION

Spinal pain, spinal cord compression, new bone formation, lymphadenomegaly and especially cortical interruption and paravertebral musculature signal intensity changes were the best discriminators for differentiating malignant from benign vertebral lesions.

Magnetic Resonance Imaging Features of Extradural Spinal Neoplasia in 60 Dogs and Seven Cats

This retrospective study describes the MRI features of extradural spinal neoplasia in 60 dogs and seven cats to identify potential distinguishing features between tumor classes and individual tumor types within each class. In dogs, mesenchymal tumors were most common (48%), with undifferentiated sarcomas being the predominant tumor type. Round cell neoplasms were second most common (35%), with lymphoma and multiple myeloma/plasma cell tumor comprising the majority of cases. Only two benign tumors were identified. In cats, lymphoma was most common (5/7), with one case of mesenchymal neoplasia and one case of metastatic carcinoma. Despite some overlap, certain imaging features were able to help prioritize differential diagnoses. The combined features that predicted round cell neoplasia (84%) included the preservation of vertebral shape, homogeneous contrast enhancement, and lesion centering on bone. The combined features that predicted mesenchymal neoplasia (73%) included altered vertebral shape, heterogeneous contrast enhancement, and lesion centering on paraspinal soft tissues. Round cell neoplasms were more likely to have cortical sparing, preservation of overall shape, lesion centering on bone, small soft tissue tumor size, and homogeneous contrast enhancement. Both epithelial and mesenchymal neoplasms were more likely to have cortical lysis, a cavitary component to the soft tissue mass and medium to large soft tissue mass size. The findings of this study can aid in prioritizing differential diagnoses in cases of extradural spinal neoplasia in cats and dogs, which can impact case management, but tissue sampling remains the gold standard for definitive diagnosis.

The number of glutamines in the N-terminal of the canine androgen receptor affects signalling intensities

Most male dogs are castrated at young ages, making them easy to rear following androgen deprivation. Although the incidence of canine prostate cancer is low, several patients have resistance to androgen therapy and poor clinical prognosis. These outcomes are similar to those of end-stage human androgen-independent prostate cancer. The androgen receptor (AR) of canines has two polyglutamine (polyQ) sequences (Q × 10 and Q × 23) at its N-terminal. The length of polyQ may be a risk factor for the development of prostate cancer in dogs; however, there is no evidence to support this. Hence, we artificially created polyQ deletion mutants of canine AR and evaluated their effects on AR signalling. The deletions of Q × 10 and Q × 23 were associated with significant reductions in AR signalling intensities. The Q × 10 mutants, which increase or decrease Q sequentially, also altered AR signalling. Furthermore, the Q × 10 deletion mutant, compared with the Q × 10 control, altered the intensities of the binding of polyQ to the C-terminal of AR, which contains a ligand-binding domain; this was not observed with the Q × 9, 11, and 12 variants. The number of glutamines in the N-terminals of canine ARs may influence AR signalling intensities and contribute to the risk of prostate cancer in dogs.

What can we learn from cancer of unknown primary in canine oncology?

Cancer of unknown primary (CUP) represents a heterogeneous group of metastatic tumors that lack an identifiable primary site despite an extensive diagnostic work-up. It is a well-recognized entity that is characterized by early dissemination, aggressive clinical course, unpredictable metastatic pattern, intrinsic treatment resistance, and a dismal prognosis. Despite the molecular diagnostic workup and personalized therapy, the expected improvements in the diagnosis and treatment of CUP have not been achieved. Comparative oncology has a promising role in the exchange of knowledge and practices between humans and canines. Therefore, we intended to review the literature reporting on CUP in dogs in order to identify some interesting parallels and unique results that could be transposed to in-human research.

Lower Urinary Tract Neoplasia

Lower urinary tract neoplasia in companion animals is a debilitating and often life-threatening disease. Tumors of the bladder, urethra, and prostate often occur independently, although extension of these tumors into adjacent regions of the lower urinary tract is documented frequently. The most common lower urinary tract tumor in dogs and cats is transitional cell carcinoma (TCC). In both dogs and cats, TCC affecting the urinary bladder is generally considered to be highly aggressive with both local and metastatic disease potential, and this disease poses unique treatment challenges. Whereas much literature exists regarding the TCC disease process, treatment options, and prognosis in dogs, relatively few studies on feline TCC have been published due to the lower incidence of TCC in this species. Prostate tumors, most commonly adenocarcinomas, occur less commonly in dogs and cats but serve an important role as a comparative model for prostate neoplasia in humans. This article serves as a review of the current information regarding canine and feline lower urinary tract neoplasia as well as the relevance of these diseases with respect to their human counterparts.

Imaging and surgical outcomes of spinal tumors in 18 dogs and one cat

Clinical and magnetic resonance imaging (MRI) findings, histological appearances and surgical outcomes of 18 dogs and one cat with spinal tumors are presented. Medical records of the cases admitted for spinal disorders were reviewed, and cases of spinal tumors that were diagnosed by MRI and confirmed by histological examination were included in this study. T1 weighted, T2 weighted and contrast enhanced T1 weighted images were taken and interpreted to evaluate the spinal tumors. The tumors were diagnosed as: meningioma (n = 6), ependymoma (n = 1), nerve sheath tumor (n = 4), metastatic spinal tumor (n = 3), osteosarcoma (n = 2), osteoma (n = 1), rhabdomyosarcoma (n = 1), and nephroblastoma (n = 1). Thirteen cases underwent surgical operation and the remaining six cases were euthanized at the request of the owners. The neurological status of the surgical cases did not deteriorate, except for one dog that showed ependymoma in the early period after the operation. These results indicate the potential for surgical gross total tumor removal of vertebral tumors to provide better quality of life and surgical collection of histological specimens for definitive diagnosis. For effective case management, dedicated MRI examination is important to accurate evaluation of the spinal tumors, and surgical treatment is useful for extradural and intradural-extramedullary spinal tumors.

Lower urinary tract cancer

Lower urinary tract neoplasia is uncommon in dogs and cats, though transitional cell carcinoma (TCC) is the most common tumor of the lower urinary tract in both species. Clinical signs are not specific for neoplasia, but neoplasia should be considered in patients that are older, have specific risk factors, or have persistent, severe, or relapsing signs. Local disease is often the cause of death or euthanasia; local control is challenging owing to tumor size and location. Systemic therapy is the mainstay of treatment. Prognosis is generally guarded, but therapy can result in improvement in clinical signs and quality of life.

Generation of a canine anti-EGFR (ErbB-1) antibody for passive immunotherapy in dog cancer patients

Passive immunotherapy with monoclonal antibodies represents a cornerstone of human anticancer therapies, but has not been established in veterinary medicine yet. As the tumor-associated antigen EGFR (ErbB-1) is highly conserved between humans and dogs, and considering the effectiveness of the anti-EGFR antibody cetuximab in human clinical oncology, we present here a "caninized" version of this antibody, can225IgG, for comparative oncology studies. Variable region genes of 225, the murine precursor of cetuximab, were fused with canine constant heavy gamma and kappa chain genes, respectively, and transfected into Chinese hamster ovary (CHO) DUKX-B11 cells. Of note, 480 clones were screened and the best clones were selected according to productivity and highest specificity in EGFR-coated ELISA. Upon purification with Protein G, the recombinant cetuximab-like canine IgG was tested for integrity, correct assembly, and functionality. Specific binding to the surface of EGFR-overexpressing cells was assessed by flow cytometry and immunofluorescence; moreover, binding to canine mammary tissue was demonstrated by immunohistochemistry. In cell viability and proliferation assays, incubation with can225IgG led to significant tumor cell growth inhibition. Moreover, this antibody mediated significant tumor cell killing via phagocytosis in vitro. We thus present here, for the first time, the generation of a canine IgG antibody and its hypothetical structure. On the basis of its cetuximab-like binding site, on the one hand, and the expression of a 91% homologous EGFR molecule in canine cancer, on the other hand, this antibody may be a promising research compound to establish passive immunotherapy in dog patients with cancer.

Occurrence of tumours metastatic to bones and multicentric tumours with skeletal involvement in dogs

The skeletons of 110 dogs with malignant tumours of different origins were examined by necropsy examination over a 3-year period to identify bone metastases. Twenty-one cases of metastatic or multicentric tumours with bone involvement were recorded. In general, more female dogs presented with bony metastases; however, when the dogs with mammary tumours were omitted, the gender distribution of the cases was approximately equivalent. The mammary gland was the primary site of most of the metastatic bone lesions, followed by the musculoskeletal system and the respiratory system. The majority (77%) of metastases were grossly visible and present in multiple bones. However, in 23% of the cases, the metastases could be diagnosed only at the microscopical level. The vertebrae and the humerus were the most frequently affected bones regardless of the primary site and the histogenesis of the tumours. The results of this study revealed a high prevalence of bone metastases and/or bone involvement in dogs with multicentric tumours.

Occult metastatic intestinal adenocarcinoma resulting in pathological fracture of the proximal humerus

Intestinal adenocarcinomas are rare but have been described in the literature. The present case is unusual in both its clinical presentation and in the distribution of metastatic lesions. The sequestrum formation and pathological fracture present are most commonly associated with osteomyelitis in horses and the details of the case highlight the need for differential diagnosis in these particular circumstances and of which clinicians should be aware.

Primary osseous melanoma in the tibia of a dog

An 18-month-old, female Cane Corso dog was presented with a suspected primary tumor of the tibia. Plain radiographs and computed tomography (CT) of the tibia were highly suggestive of a primary bone neoplasm. A diagnosis of malignant melanoma was made by cytology. Total body survey radiographs, CT scan of the thorax, and abdominal ultrasound excluded the presence of neoplastic lesions other than in the tibia. Limb amputation was performed. Histology and immunohistochemical analysis of the tibial neoplasm confirmed the diagnosis of a melanoma with secondary metastasis to the popliteal lymph node. The dog was alive and in good physical condition 43 months after surgery.

A population study of neutering status as a risk factor for canine prostate cancer

BACKGROUND

Prostate cancer has been reported to occur more commonly in neutered than intact male dogs in several case series. This study was undertaken to evaluate risk of prostate cancer in a large population database. The hypothesis was that castration is a risk factor for prostate cancer in male companion dogs.

METHODS

Data were derived from recorded visits to North American veterinary teaching hospitals. The Veterinary Medical Databases (VMDB) were queried to yield male dogs with urinary bladder transitional cell carcinoma (TCC), prostate adenocarcinoma (ACA), prostate TCC, prostate carcinoma (CA), and prostate tumors. A second query yielded all male dogs over the age of 4 years without a diagnosis of urinary tract cancer. These populations were compared to determine relative risks for developing each disease, singly and collectively, associated with neutering status. Odds ratios were calculated for breed as a risk factor.

RESULTS

Neutered males had a significantly increased risk for each form of cancer. Neutered males had an odds ratio of 3.56 (3.02-4.21) for urinary bladder TCC, 8.00 (5.60-11.42) for prostate TCC, 2.12 (1.80-2.49) for prostate adenocarcinoma, 3.86 (3.13-4.16) for prostate carcinoma, and 2.84 (2.57-3.14) for all prostate cancers. Relative risks were highly similar when cases were limited to those with a histologically confirmed diagnosis.

CONCLUSIONS

Breed predisposition suggests that genetic factors play a role in the development of prostate cancer. The risk associated with being neutered is highest for TCC, supporting previous work identifying the urothelium and ductular rather than acinar epithelium as the source of these tumors.

Lameness in a dog caused by thoracic wall invasion by a pulmonary neoplasm

A 12-year-old fox-terrier dog presented with forelimb lameness of 3-weeks duration. Ultrasonography revealed a mass within the thoracic wall and osteolysis of the left third rib. A squamous cell carcinoma was diagnosed by cytological examination of an ultrasound-guided fine needle aspirate of this mass. As a result of the diagnosis of neoplasia, the dog was euthanatized. Necropsy revealed a solitary expansile mass within the left cranial lung lobe, and a mass within the adjacent thoracic wall. Thickening of the pleura between the two masses was visible, although adhesions were not present. Histology of both masses revealed a well-differentiated squamous cell carcinoma. To the authors' knowledge, this is the first detailed description of direct invasion of the thoracic wall by a canine lung tumour.

Nuclear imaging of Met-expressing human and canine cancer xenografts with radiolabeled monoclonal antibodies (MetSeek)

PURPOSE

Met, an oncogene product and receptor tyrosine kinase, is a keystone molecule for malignant progression in solid human tumors. We are developing Met-directed imaging and therapeutic agents, including anti-Met monoclonal antibodies (MetSeek). In this study, we compared two antibodies, Met5 and Met3, for nuclear imaging of human and canine Met-expressing tumor xenografts in nude mice.

EXPERIMENTAL DESIGN

Xenografts representing cancers of three different human tissue origins and metastatic canine prostate cancer were raised s.c. in host athymic nude mice. Animals were injected i.v. with I-125-Met5 or I-125-Met3, posterior total body gamma camera images were acquired for several days postinjection, and quantitative region-of-interest activity analysis was done.

RESULTS

PC-3, SK-LMS-1/HGF, and CNE-2 xenografts imaged with I-125-Met5 were compared with PC-3, SK-LMS-1/HGF, and DU145 xenografts imaged with I-125-Met3. Nuclear imaging contrast was qualitatively similar for I-125-Met5 and I-125-Met3 in PC-3 and SK-LMS-1/HGF host mice. However, by region-of-interest analysis, the set of human tumors imaged with I-125-Met3 exhibited a pattern of rapid initial tumor uptake followed by a continuous decline in activity, whereas the set of human tumors imaged with I-125-Met5 showed slow initial uptake, peak tumor-associated activity at 1 day postinjection, and persistence of activity in xenografts for at least 5 days. GN4 canine prostate cancer xenografts were readily imaged with I-125-Met5.

CONCLUSIONS

We conclude that radioiodinated Met3 and Met5 offer qualitatively similar nuclear images in xenograft-bearing mice, but quantitative considerations indicate that Met5 might be more useful for radioimmunotherapy. Moreover, canine prostate cancer seems to be a suitable model for second-stage preclinical evaluation of Met5.

Firm rib mass aspirate from a dog

A 9-year-old intact male Miniature Schnauzer presented laterally recumbent, cachexic, and dehydrated with multiple firm bone masses and a bilaterally enlarged prostate. Fine-needle aspiration of a rib mass revealed numerous basophilic polygonal to fusiform cells predominantly found in small to large clusters. The cells exhibited cytologic criteria of malignancy and infrequently displayed large cytoplasmic vacuoles containing finely- to coarsely-stippled azurophilic material. The cytologic diagnosis was metastatic adenocarcinoma and was suspected to be prostatic or transitional cell in origin because of the azurophilic vacuoles within malignant cells. Gross and histologic findings confirmed the clinical and cytologic diagnosis of prostatic adenocarcinoma with widespread metastasis. Cytochemical and immunohistochemical investigation confirmed glycogen was a component of the vacuolar material. The vacuoles observed in the tumor in this case are not a consistent finding in tumors of the prostate or urinary bladder; however, when associated with an epithelial tumor, they may aid in limiting the differentials of the primary tumor and in the selection of further diagnostics.

Intercalary Bone Grafts for Joint and Limb Preservation in 17 Dogs with High-Grade Malignant Tumors of the Diaphysis

OBJECTIVE

To evaluate postoperative complications, limb function, and tumor control after intercalary resection and reconstruction for preservation of limb and joint function in dogs with high-grade malignant tumors of diaphyseal bone.

STUDY DESIGN

Retrospective study.

ANIMALS

Seventeen client-owned dogs.

METHODS

The bone tumor database and medical records were reviewed (1986-2002) for dogs with diaphyseal tumors treated with intercalary resection and reconstruction with either an allograft or irradiated autograft. Clinical presentation, diagnostic findings, surgical management, and outcome were determined from medical records and telephone interviews with veterinarians and owners. Statistical analyses included chi2 to test associations between intra- and postoperative variables with complications, and Kaplan-Meier survival analysis for disease-free interval, metastasis-free interval (MFI), and median survival time.

RESULTS

Intercalary limb-sparing surgery was performed in 17 dogs with diaphyseal tumors: osteosarcoma (OSA) (15), histiocytic sarcoma (1), and solitary metastasis from a pulmonary adenocarcinoma (1). One dog was excluded from further analysis when the spared limb was amputated 4 days postoperatively because of incomplete tumor resection. In 16 dogs, limb function was good to excellent. Complications occurred in 5 dogs (31.3%) and included superficial infection in 2 dogs (12.5%) and implant failure in 4 dogs (25%). All implant failures occurred in the ulna and there was a significant association between implant failure and non-cemented allografts (P=.042). Non-union of 1 or both osteotomies was diagnosed in 10 dogs (83.3%) and, despite lack of clinical signs in all cases, was significantly associated with the use of intracavitary locally released cisplatin (P=.046) and cemented intercalary grafts (P=.046). Local tumor recurrence was diagnosed in 1 dog (6.3%) and metastatic disease in 12 dogs (75.0%), including 10 dogs with OSA. The median MFI was 137 days. The local disease-free and overall limb-salvage rate was 94% and 100%, respectively. Overall median survival time was 393 days and the median survival time for dogs with OSA was 449 days.

CONCLUSION

Intercalary limb-sparing surgery results in better postoperative limb function with fewer and less severe complications than historical reports of dogs treated with non-intercalary limb-sparing surgery.

CLINICAL RELEVANCE

In dogs with diaphyseal tumors, intercalary limb-sparing surgery preserves normal joint function and results in good to excellent limb use with few complications and good local tumor control.

Clinical and pathologic aspects of spontaneous canine prostate carcinoma: a retrospective analysis of 76 cases

BACKGROUND

Pet dogs and men share a vulnerability for the development of prostate carcinoma. The purpose of this study was to further characterize the clinical and pathologic features of spontaneous canine prostate carcinoma.

METHODS

A multiinstitutional, retrospective study was conducted using 76 dogs with prostate carcinoma that underwent postmortem evaluation. For each case, clinical and pathologic data were tabulated and hematoxylin/eosin-stained tissue sections from the primary tumor and metastatic lesions were evaluated. Prostatic carcinomas were subclassified based upon the presence of glandular, urothelial, squamoid, or sarcomatoid differentiation. We focused our analysis on dogs that differed with respect to morphologic features of the primary tumor, lifetime duration of testicular hormone exposure, and presence of skeletal metastases.

RESULTS

The vast majority of canine prostate carcinomas affected elderly sexually intact dogs or dogs that underwent surgical castration after sexual maturity. Adenocarcinoma was the most frequent histologic type, although more than half of canine prostate carcinomas exhibited intratumoral heterogeneity. In many cases, primary tumors showed mixed morphology, characterized by two or more types of differentiation. Duration of testicular hormone exposure was significantly different between dogs with adenocarcinoma and dogs with mixed morphology tumor, but did not appear to influence the frequency or pattern of metastases. Overall, gross metastases were present in 80% of dogs with prostate carcinoma. Skeletal metastases were present in 22% of cases, and the predominantly axial skeletal distribution of these lesions was similar to that reported in men with prostate carcinoma. Young dogs were at highest risk for development of skeletal metastases.

CONCLUSIONS

This study provides a more complete characterization of spontaneous prostate carcinoma of dogs in terms of morphologic heterogeneity, skeletal metastases, and the influence of testicular hormones. Prostate carcinoma in pet dogs provides an immunocompetent, autochthonous tumor system that mimics certain aspects of human prostate cancer. This spontaneous model may contribute to our understanding of the factors that regulate carcinogenesis within the aged prostate, and to the development of chemoprevention strategies or bone-targeted therapies.