Outcome following treatment of soft tissue and visceral extraskeletal osteosarcoma in 33 dogs: 2008-2013.

Extraskeletal osteosarcoma (EOS) is a rare, highly malignant mesenchymal neoplasm arising from viscera or soft tissues characterised by the formation of osteoid in the absence of bone involvement. Owing to the rarity of these neoplasms very little information exists on treatment outcomes. The purpose of this study was to describe the outcome following surgical treatment of non-mammary and non-thyroidal soft tissue and visceral EOS in dogs. Thirty-three dogs were identified; the most common primary tumour site was the spleen. Dogs that had wide or radical tumour excision had longer survival times compared with dogs that had only marginal tumour excision performed [median survival time of 90 days (range: 0-458 days) versus median survival time of 13 days (range: 0-20 days)]. The use of surgery should be considered in the management of dogs with non-mammary and non-thyroidal soft tissue and visceral EOS.

DOG1 is a sensitive and specific immunohistochemical marker for diagnosis of canine gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) and leiomyosarcomas are histologically similar primary neoplasms commonly occurring in the gastrointestinal tract of dogs and humans. Immunohistochemical staining (IHC) is needed to differentiate between these 2 entities and positive reactivity for KIT (cluster of differentiation [CD]117) is regarded as the gold standard for diagnosis of canine GIST. Studies estimate 5-10% of human GISTs stain negative or only weakly positive for KIT and have identified DOG1 (discovered on gastrointestinal stromal tumors protein 1) as a highly sensitive and specific marker for human GISTs. The purpose of this study was to evaluate immunoreactivity of a commercially available DOG1 antibody for use in diagnosis of canine GISTs. Fifty-five primary mesenchymal gastrointestinal tumors with histologic features consistent with GIST or leiomyosarcoma were evaluated via IHC for KIT, DOG1, and desmin. A subset of tumors was additionally evaluated for reactivity for smooth muscle actin (SMA). Thirty-three tumors (60%) were diagnosed as GIST based on positive immunoreactivity for KIT or DOG1 regardless of reactivity for desmin or SMA. Most GISTs (32/33, 97.0%) had similar staining for both KIT and DOG1. DOG1 expression was identified in 2 tumors (1 study tumor and 1 additional tumor) negative for KIT and desmin that had histologic features consistent with KIT-negative, platelet-derived growth factor receptor-alpha (PDGFRA)-mutant human GISTs. Our results suggest that DOG1 has improved specificity and sensitivity to that of KIT for differentiating between canine GISTs and leiomyosarcomas. Inclusion of both DOG1 and KIT IHC in diagnostic panels will improve the accuracy of canine GIST diagnosis.

Prognostic significance of histologic features in canine renal cell carcinomas: 70 nephrectomies.

The prognostic significance of histologic and clinical features was evaluated in a retrospective study of 70 dogs treated with nephrectomy for renal cell carcinoma. Dogs presenting with hematuria and cachexia had significantly decreased overall and tumor-specific survival. Mitotic index (MI), nuclear size, nuclear pleomorphism, tumor differentiation, invasiveness, Fuhrman nuclear grade, and clear cell morphology were significantly associated with survival times (overall and tumor specific) in univariate analyses. A multivariate Cox proportional hazards model was constructed using stepwise selection to evaluate potential histologic predictor variables. This multivariate analysis revealed MI, defined as the number of mitotic figures in ten 400× fields, as the sole independent prognostic variable. Median survival for dogs with an MI >30 was 187 days compared with 1184 days for dogs with an MI of <10. Dogs with an intermediate MI of 10 to 30 had a median survival of 452 days. Canine renal carcinomas were categorized into the following subtypes based on histologic features and histochemical and immunohistochemical staining: (1) clear cell, (2) chromophobe, (3) papillary, and (4) multilocular cystic renal cell carcinomas. Clear cell carcinoma was diagnosed in 6 of 70 (9%) canine tumors and was associated with a significantly decreased median survival time. Papillary carcinomas were identified in 15 of 70 tumors (21%), chromophobe in 6 of 70 (9%), and the multilocular cystic variant of canine renal cell carcinoma in 3 of 70 tumors (4%). These findings facilitate uniform categorization of canine renal cell carcinoma and provide veterinary pathologists with criteria to determine prognostic information.

Clinical outcome in 20 cases of lingual hemangiosarcoma in dogs: 1996-2011.

With the exception of solar-induced dermal hemangiosarcoma (HSA), the biologic behaviour of canine HSA is characterised by rapid tumour growth, a high metastatic rate and short survival times. Outcome of dogs with HSA of the tongue has not been previously reported. The purpose of this study was to assess outcome and prognostic factors in dogs with lingual HSA. Clinical data was collected retrospectively and histopathology was reviewed for 20 dogs. Median progression free survival was 524 days and the median overall survival time was 553 days. All dogs had low or intermediate grade tumours; most tumours were small and located on the ventral surface of the tongue. Prognostic factors significantly associated with increased survival included small tumour size and absence of clinical signs of an oral mass at the time of diagnosis. Dogs with HSA confined to the tongue may have a better prognosis compared with HSA in other organs.

Elution of antimicrobials from a cross-linked dextran gel: In vivo quantification.

REASONS FOR PERFORMING STUDY: Use of a novel, biodegradable, antimicrobial-impregnated gel provides an alternative method of local treatment of infections in horses. OBJECTIVES: To determine in vivo elution of antimicrobial medications from antimicrobial-impregnated cross-linked dextran gel and to evaluate the effect on wound healing when implanted subcutaneously in horses. METHODS: Amikacin-, vancomycin- or amikacin/clindamycin-impregnated gel was placed subcutaneously in 11 horses' necks, using 6 replicates with a 3 month washout between experiments. Capillary ultrafiltration probes for collection of interstitial fluid were placed 0 cm and 1.5 cm from the gel-filled incisions. Samples were collected at 0, 4, 8 and 12 h, and on Days 1-10. Blood was collected on Days 0, 1 and 7. Amikacin and vancomycin samples were analysed via fluorescence polarisation immunoassay, and clindamycin samples via high-performance liquid chromatography. Histology of biopsy samples was performed at the completion of the study. Differences in mean histomorphological scores between groups were assessed using Wilcoxon's signed ranks test. RESULTS: Maximum antimicrobial concentrations were detected at 4 h (amikacin), and 8 h (vancomycin, and amikacin and clindamycin from the combination gel). Mean ± s.d. peak concentrations for amikacin, vancomycin, amikacin (amikacin/clindamycin) and clindamycin were 6133 ± 1461, 7286 ± 2769, 3948 ± 317 and 985 ± 960, respectively. Median number of days for which antimicrobial concentration remained above minimum inhibitory concentration for target microorganisms at implantation was ≥10 days for vancomycin, 9 days (± 1) for amikacin and 8 days (± 1) for clindamycin. Mean plasma amikacin and vancomycin concentrations were lower than detectable limits; mean serum clindamycin concentrations were 0.52 µg/ml and 0.63 µg/ml at 24 h and 7 days, respectively. There were no significant differences in histomorphological scores between treatment and control incisions (P≥0.22). CONCLUSIONS AND POTENTIAL RELEVANCE: Cross-linked dextran gel is a safe, effective alternative local antimicrobial delivery method.

Prognostic factors for cutaneous and subcutaneous soft tissue sarcomas in dogs.

Soft tissue sarcomas (STSs) develop from mesenchymal cells of soft tissues, and they commonly occur in the skin and subcutis of the dog. Although phenotypically diverse with frequently controversial histogenesis, STSs are considered as a group because they have similar features microscopically and clinically. Following resection, local recurrence rates are low in general but vary according to histologic grade and completeness of surgical margins. Complete margins predict nonrecurrence. Even most grade I STSs with "close" margins will not recur, but propensity for recurrence increases with grade. The frequency of metastasis has not been accurately estimated, but it is believed to be rare for grade I STSs and most likely to occur with grade III STSs. However, metastasis does not necessarily equate with poor survival. High mitotic index is prognostic for reduced survival time. Further research is needed to determine more precise estimates for recurrence rates and survival as related to completeness of surgical margins and to delineate potential differences in metastatic rate and median survival time between grades. Other potential indicators of prognosis that presently require further investigation include histologic type, tumor dimension, location, invasiveness, stage, markers of cellular proliferation, and cytogenetic profiles. Common issues limiting prognostic factor evaluation include biases from retrospective studies, small sample sizes, poor verification of metastasis, inconsistent STS classification and use of nomenclature, difficulties in differentiating STS phenotype, and diversity of the study population (stage of disease and treatment status).

Recommended guidelines for submission, trimming, margin evaluation, and reporting of tumor biopsy specimens in veterinary surgical pathology.

Neoplastic diseases are typically diagnosed by biopsy and histopathological evaluation. The pathology report is key in determining prognosis, therapeutic decisions, and overall case management and therefore requires diagnostic accuracy, completeness, and clarity. Successful management relies on collaboration between clinical veterinarians, oncologists, and pathologists. To date there has been no standardized approach or guideline for the submission, trimming, margin evaluation, or reporting of neoplastic biopsy specimens in veterinary medicine. To address this issue, a committee consisting of veterinary pathologists and oncologists was established under the auspices of the American College of Veterinary Pathologists Oncology Committee. These consensus guidelines were subsequently reviewed and endorsed by a large international group of veterinary pathologists. These recommended guidelines are not mandated but rather exist to help clinicians and veterinary pathologists optimally handle neoplastic biopsy samples. Many of these guidelines represent the collective experience of the committee members and consensus group when assessing neoplastic lesions from veterinary patients but have not met the rigors of definitive scientific study and investigation. These questions of technique, analysis, and evaluation should be put through formal scrutiny in rigorous clinical studies in the near future so that more definitive guidelines can be derived.

Feline intestinal sclerosing mast cell tumour: 50 cases (1997-2008).

This case series presents a unique and unreported variant of feline intestinal mast cell tumour recognized at the CSU Veterinary Diagnostic Laboratory. Fifty cases of feline intestinal mast cell tumours described as having a significant stromal component were reviewed. Neoplastic cells formed a trabecular pattern admixed with moderate to abundant dense stromal collagen (sclerosis). Neoplastic cells had poorly discernible intracytoplasmic granules which demonstrated metachromasia with special histochemical stains consistent with mast cell granules. Additionally, a subset of cases stained for mast cell-specific tryptase and c-kit demonstrated positive immunoreactivity. Eosinophilic infiltrates were moderate to marked in almost all cases. Lymph node and hepatic metastases were present in 66% of the cases. Treatment and clinical outcome was available in 25/50 cases. Twenty-three of these patients died or were euthanized within 2 months of initial diagnosis. This is the first case series to characterize a sclerosing variant of intestinal mast cell tumour in the cat which appears to have a high propensity for metastasis and a guarded prognosis.

Alkaline hydrolysis of mouse-adapted scrapie for inactivation and disposal of prion-positive material.

Prion diseases such as bovine spongiform encephalopathy, chronic wasting disease, and scrapie pose serious risks to human and animal health due to a host of disease-specific factors, including the resistance of infectious prions (PrP(Sc)) to natural degradation and to most commercial inactivation procedures. In an attempt to address this concern, a mouse model was used to compare the efficacy of an alkaline hydrolysis process with a simulated continuous-flow rendering treatment for disposal of PrP(Sc)-infected biological material. Female C57/BL6 mice (N = 120) were randomly divided into 4 treatment groups (n = 30), and each mouse was injected intraperitoneally with their designated treatment inoculum. Treatment groups 1 and 2 served as the positive and negative controls, respectively. Group 3 was inoculated with rendered scrapie-positive mouse brain material to investigate the effectiveness of simulated continuous-flow rendering practices to reduce or eliminate PrP(Sc). Group 4 was inoculated with hydrolyzed scrapie-positive mouse brain material to determine the sterilizing effect of alkaline hydrolysis on PrP(Sc). Mice were monitored for overt signs of disease, and those showing clinical signs were killed to prevent undue suffering. Brains were obtained from all mice that died (or were killed) and analyzed with an ELISA for the presence of PrP(Sc). Results indicated that the simulated continuous-flow rendering treatment used for preparing the rendering treatment group inoculum failed to completely eliminate PrP(Sc). Rendering delayed, but did not stop, clinical mouse-adapted scrapie transmission. Compared with positive controls, the rendering treatment group experienced an approximate 45-d average delay in days to death (250 vs. 205 d for positive controls; P < 0.0001) and a death loss of 73.9% (P = 0.0094). Positive controls suffered 100% death loss. The results validated the efficacy of the alkaline hydrolysis treatment to inactivate all PrP(Sc) because no alkaline hydrolysis treatment group mice succumbed to the disease (P < 0.0001). Based on our results, alkaline hydrolysis should be considered by the animal rendering and beef packing industries as an alternative to incineration, landfill burial, and rendering for disposing of biological material potentially infected or contaminated with prion disease.

Hyalinizing pancreatic adenocarcinoma in six dogs.

Exocrine pancreatic carcinoma is a particularly malignant neoplasm of the dog. Clinical and pathologic findings of an unusual variant of exocrine pancreatic neoplasia termed hyalinizing pancreatic adenocarcinoma were evaluated in 6 dogs. On microscopic examination, neoplasms were composed of tubules and acini of epithelial cells, with bright eosinophilic granular apical cytoplasm. Tubular lumina and tumor stroma contained abundant hyaline material that resembled amyloid. The hyaline material was not congophilic, and tumor cells and hyaline material were immunohistochemically negative for amyloid A, immunoglobulin light chains (kappa and lambda), amylin (islet amyloid polypeptide), laminin, and alpha(1)-antitrypsin. Two patients survived longer than 15 months after diagnosis; one of these dogs was untreated and had grossly evident metastasis at the time of diagnosis. The deaths of the other 4 dogs occurred as a result of poor recovery after partial pancreatectomy or in association with other concurrent life-threatening conditions. Two dogs were diagnosed with panniculitis, a condition rarely associated with pancreatic disease. Further evaluation is needed to determine the composition and biologic significance of intratumor hyaline material. Studies that associate exocrine pancreatic carcinoma grade and histologic subtype with prognostic outcomes in the dog are warranted such that appropriate therapy can be elected.

Diagnoses and clinical outcomes associated with surgically amputated canine digits submitted to multiple veterinary diagnostic laboratories.

Amputation is commonly performed to both treat and diagnose conditions affecting the digits of dogs. Although histopathologic evaluation of these digits is routinely done, data on the prevalence and prognosis of neoplasms of the digit are scarce. The records of multiple veterinary diagnostic laboratories were searched to identify submissions of amputated digits from dogs. Four hundred twenty-eight separate submissions were reviewed for diagnosis, age, sex, limb of origin, and digits affected, and the original submitting clinics were surveyed to determine clinical outcome of the animal. No diagnosis could be agreed upon in 24 animals, and these were excluded from the study. Kaplan-Meier product-limit method was used to determine the disease-free interval and survival time. Neoplastic disease was identified in 296 of 404 submissions, with exclusively inflammatory lesions composing 108 cases. A total of 30 different neoplastic processes were identified. In 233 (77.7%) of the neoplastic cases, a malignant tumor was identified. Squamous cell carcinoma was the most commonly identified tumor (n = 109, 36.3%), and 11 of 42 dogs for which clinical follow-up information was available developed metastatic disease. Squamous cell carcinoma of the digit appears to have a greater metastatic potential than that occurring elsewhere in the body. Other common diagnoses included melanoma (n = 52, 17.3%), soft-tissue sarcoma (n = 29, 9.7%), and mast cell tumor (n = 20, 6.7%). Melanomas were associated with poor prognoses, with a median survival time of 365 days.

Diagnoses and clinical outcomes associated with surgically amputated feline digits submitted to multiple veterinary diagnostic laboratories.

Amputation is commonly performed in an attempt to both treat and diagnose conditions affecting the digits of cats. The records of multiple veterinary diagnostic laboratories were searched to identify submissions of amputated digits from cats. Eighty-five separate submissions were reviewed for diagnosis, age, sex, limb of origin, and digits affected; and the original submitting clinics were surveyed to determine clinical outcome. The Kaplan-Meier product-limit method was used to determine the disease-free interval and survival time. Neoplastic disease was identified in 63 of 85 submissions, with exclusively inflammatory lesions composing the other 22 cases. In 60 (95.2%) of the neoplastic cases, a malignant tumor was identified. Squamous cell carcinoma was the most commonly identified malignant tumor (n = 15; 23.8%) and was associated with a median survival time of 73 days. Other diagnoses included fibrosarcoma (n = 14; 22.2%); adenocarcinoma, likely metastases of a primary pulmonary neoplasm (n = 13; 20.6%); osteosarcoma (n = 5; 7.9%); mast cell tumor (n = 4; 6.3%); hemangiosarcoma (n = 5; 7.9%); malignant fibrous histiocytoma (n = 2; 3.2%); giant cell tumor of bone (n = 2; 3.2%); and hemangioma (n = 2; 3.2%). Giant cell tumor of bone has not been previously described in the digits of cats. Various neoplasms can occur in the digits of cats, and submission of the amputated digit for histopathologic diagnosis is essential to determine the histogenesis and predict the clinical outcome.

Cytological comparison of fine-needle aspirates of liver and spleen of normal dogs and of dogs with cutaneous mast cell tumours and an ultrasonographically normal appearing liver and spleen.

Staging of dogs with cutaneous mast cell tumours (MCTs) is an important diagnostic step. Aspiration of the liver and the spleen is often part of routine staging. This study cytologically compared mast cell numbers in fine-needle aspirates of liver and spleen of clinically normal unaffected dogs with those of dogs with cutaneous MCT and an ultrasonographically normal appearing liver and spleen. The unaffected dogs (n = 32) were selected from humane society dogs, and the affected dogs (n = 51) were selected from hospital cases. There were no statistically significant differences in each of the parameters evaluated for the liver aspirates. For splenic aspirates, affected dogs showed significantly more mast cells per cluster (P = 0.04) and more isolated mast cells per slide (P = 0.03) compared with unaffected dogs. However, no clinically important difference existed between the unaffected and affected dogs; thus, routine aspiration of an ultrasonographically normal appearing liver and spleen of dogs with cutaneous MCT does not appear to be a clinically useful staging tool.

Tetrachlorodibenzo-p-dioxin exposure alters radial arm maze performance and hippocampal morphology in female AhR mice.

Perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been reported to alter spatial learning in rats tested on a radial arm maze (RAM). TCDD is believed to exert most of its effects through binding to the aryl hydrocarbon receptor (AhR). To determine whether the AhR mediates TCDD-induced alterations in spatial learning, we tested male and female AhR-knockout (AhR-/-), heterozygous (AhR+/-) and wild-type (AhR+/+) mice on the RAM. AhR+/- male and female mice were time mated, and treated dams were dosed with 5 microg TCDD/kg body weight on day 13 of gestation. When offspring reached adulthood, male and female AhR+/+, AhR+/- and AhR-/- mice from TCDD-exposed and unexposed litters were tested on the eight-arm RAM. After testing, we examined hippocampal morphology as visualized by the Timm's silver sulfide stain. TCDD-exposed female AhR+/- mice made more errors than their respective controls on the RAM and exhibited a decrease in the size of the intra- and infrapyramidal mossy fiber (IIP-MF) field of the hippocampus. None of the other TCDD-exposed groups differed from their respective control groups with regard to maze performance or hippocampal morphology. The reduction of IIP-MF field indicates a possible morphological basis for the learning deficit that was observed in the female AhR+/- mice. It is hypothesized that the effect of TCDD exposure is AhR dependent and that TCDD may alter GABAergic activity in the hippocampus of female mice during development.

Validation of monoclonal antibody F99/97.6.1 for immunohistochemical staining of brain and tonsil in mule deer (Odocoileus hemionus) with chronic wasting disease.

A new monoclonal antibody (MAb), F99/97.6.1, that has been used to demonstrate scrapie-associated prion protein PrP(Sc) in brain and lymphoid tissues of domestic sheep with scrapie was used in an immunohistochemistry assay for diagnosis of chronic wasting disease (CWD) in mule deer (Odocoileus hemionus). The MAb F99/97.6.1 immunohistochemistry assay was evaluated in brain and tonsil tissue from 100 mule deer that had spongiform encephalopathy compatible with CWD and from 1,050 mule deer outside the CWD-endemic area. This MAb demonstrated abnormal protease-resistant prion protein (PrP(res)) in brains of all of the 100 mule deer and in 99 of the 100 tonsil samples. No immunostaining was seen in samples collected from deer outside the endemic area. MAb F99/97.6.1 demonstrated excellent properties for detection of PrP(res) in fresh, frozen, or mildly to moderately autolytic samples of brain and tonsil. This immunohistochemistry assay is a sensitive, specific, readily standardized diagnostic test for CWD in deer.

Spontaneous regression of osteosarcoma in four dogs.

Spontaneous regression of primary malignant bone tumors is rare but has been reported in the human literature. To the authors' knowledge, spontaneous regression of primary bone tumors in dogs or cats has not been reported. Osteosarcoma (OSA) is the most common primary bone tumor in humans, and it has been reported that the incidence of OSA is 40 to 50 times greater in dogs than humans. In this report, high-grade OSA was diagnosed in biopsy specimens obtained from 4 dogs that subsequently underwent spontaneous regression without tumor-specific treatment. Osteosarcoma in dogs has characteristics similar to that of OSA in humans.

Evaluation of opioid receptors in synovial membranes of horses.

OBJECTIVE: To evaluate mu-opioid receptors in synovial membranes of horses and determine whether these receptors are up-regulated in nerve endings during inflammation. SAMPLE POPULATION: Synovial tissue obtained from 39 client-owned horses during arthroscopy and 14 research horses during necropsy; brain and synovial tissues were obtained during necropsy from 1 horse, and control tissues were obtained from a mouse. PROCEDURE: Horses were classified into 7 groups on the basis of histologically determined degree of inflammation. Binding of primary rabbit antibody developed against mu-opioid receptors in equine synovial tissue was studied, using western blot analysis. Synovial membranes were tested for mu-opioid receptors by immunohistochemical staining, using a diaminobenzidine-cobalt chloride chromogen. Homogenates of synovial membranes were evaluated by use of radioligand binding. RESULTS: Examination of western blots of equine thalamus revealed that rabbit antibody developed against mu-opioid receptors yielded a band (molecular weight, 55 kd) that corresponded with that of other opioid receptors. Use of immunohistochemical staining of synovial tissue revealed considerable staining in the proliferative lining layer and in regions surrounding vascular structures. Specific radioligand binding of tissue homogenates was found in all groups. We did not detect significant differences in binding between horses with inflammation and horses without inflammation. CONCLUSIONS AND CLINICAL RELEVANCE: Results of immunohistochemical analysis and radioligand binding of tissue homogenates suggest that there are opioid receptors in synovial membranes of horses. Our results support the practice of intra-articular administration of opioids to relieve pain after arthroscopic surgery in horses.

Effect of gas-plasma sterilization on the osteoinductive capacity of demineralized bone matrix.

The current study evaluated the effect of low-temperature hydrogen peroxide gas plasma sterilization on the osteoinductive capability of human demineralized bone matrix using a rat model. Twelve athymic rats received three separate implants consisting of steam-sterilized demineralized bone matrix (negative control), sterile-harvest demineralized bone matrix (positive control), and gas-plasma-sterilized demineralized bone matrix. A demineralized bone matrix pellet from each sterilization group was placed individually into one of three separate soft tissue pockets created in the epaxial musculature of each rat. All 12 rats were euthanized 9 weeks after implantation. Each implantation site was removed along with 0.5-cm normal tissue around the implant. Histologic examination was done on each implant site to determine the presence or absence of new bone, cartilage, or bone marrow elements. All 12 sterile harvest demineralized bone matrix sites histologically contained new bone elements, whereas none of the negative control or gas plasma sterilized demineralized bone matrix sites contained any of these same elements. The results of this study indicate that demineralized bone matrix sterilized with low-temperature, gas-plasma sterilization loses its osteoinductive capacity in a manner similar to that of steam-sterilized demineralized bone matrix, making low-temperature, gas- plasma sterilization unsuitable as a method of secondary sterilization of demineralized bone matrix.

Accuracy of radiography, nuclear scintigraphy, and histopathology for determining the proximal extent of distal radius osteosarcoma in dogs.

OBJECTIVE: To compare the accuracy of radiography, nuclear scintigraphy, and histopathology for determining the proximal extent of distal radius osteosarcoma in dogs. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Twenty client-owned dogs taken to Colorado State University with osteosarcoma of the distal radius. METHODS: Medical records of 20 dogs with confirmed osteosarcoma that underwent a limb-salvage procedure were reviewed. Measurements were performed directly from the lateral view of each radius, from both the scintigram and the radiograph, to determine the length of the radius and the distance from the proximal extent of the tumor to the distal radiographic or scintographic extent of the radius. The ratio of distal radial involvement to total radius length was calculated. A similar ratio was also determined using the macroslide, which included the entire portion of bone that was excised during the limb-salvage procedure. All 3 methods of measurement were compared. RESULTS: Nuclear scintigraphy significantly overestimated tumor length when compared with macroslide specimen measurements. Radiography also overestimated tumor length, but these results were not significantly different from macroslide specimen measurements. CONCLUSIONS: Both radiography and nuclear scintigraphy overestimate the extent of distal radius osteosarcoma in dogs when compared with histopathologic macroslides of the same lesions. Nuclear scintigraphy overestimated tumor extent to a larger degree than did radiography. CLINICAL RELEVANCE: Although radiography is a more accurate method of measurement of the extent of distal radius osteosarcoma, because nuclear scintigraphy overestimates tumor length to a greater degree, scintigraphy may provide a larger margin of safety for determining the site of proximal osteotomy during a limb-salvage procedure. However, caution should be taken when utilizing scintigraphy, because this method may overestimate length of radius involved to such an extent as to cause the surgeon to believe that a patient is not a suitable limb-salvage candidate.

Clinical outcome of dogs with grade-II mast cell tumors treated with surgery alone: 55 cases (1996-1999).

OBJECTIVE: To determine outcome for dogs with grade-II mast cell tumors treated with surgery alone. DESIGN: Retrospective study. ANIMALS: 55 dogs. PROCEDURES: Medical records were examined, and signalment; location and size of tumor; staging status; dates of local recurrence, metastasis, death, or last follow-up examination; status of surgical margins; previous surgery; postoperative complications; and cause of death were recorded. Follow-up information was obtained via reexamination or telephone conversations with owners or referring veterinarians. Univariate analysis was performed to identify prognostic factors. RESULTS: 60 tumors in 55 dogs were included. Median follow-up time was 540 days. Three (5%) mast cell tumors recurred locally; median time to local recurrence was 62 days. Six (11%) dogs developed another mast cell tumor at a different cutaneous location; median time to a different location was 240 days. Three (5%) dogs developed metastases; median time to metastasis was 158 days. Fourteen dogs died; 3 deaths were related to mast cell tumor, and 7 were unrelated. The relationship with mast cell tumor was not known for 4. Median survival times were 151, 841, and 827 days, respectively, for these 3 groups. Forty-six (84%) dogs were free of mast cell tumors during the study period. A reliable prognostic factor could not be identified. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that additional local treatment may not be required after complete excision of grade-II mast cell tumors and that most dogs do not require systemic treatment.