A Statistical Study on the Tumours of Dogs

The author presents a statistical investigation of tumours from 164 dogs examined at the Department of Pathology of the College of Veterinary Medicine, Helsinki, Finland.It was found that Boxers and Airedale terriers were predisposed to tumours and especially to cutaneous neoplasms. The dominance of mammary tumours in Dachshunds was statistically highly significant. A statistically highly significant under-representation of Finnish harriers and Finnish spitzes was noted.Sex distribution was female-dominated, obviously owing to high incidence of mammary tumours.It was shown that tumours, especially malignant neoplasms, were primarily found in the high age groups.No difference was observed in the frequency of epithelial and mesenchymal tumours. Malignant tumours were strongly dominant, obviously due to common incidence of carcinoma. The carcinoma/sarcoma ratio was 1.5:1.Analysis of the localization showed that cutaneous tumours (37.0 %) and mammary tumours of females (19.1 %) were most common.Nine dogs showed 18 multiple primary tumours. The high frequency of these tumours in older dogs was obvious. Their mean age was 10 ± 0.9 year.     

Relationships between the histological grade of cutaneous mast cell tumours in dogs, their survival and the efficacy of surgical resection

The histological grade of 340 cutaneous mast cell tumours derived from 280 dogs was determined by an established histological grading system; 87 of the tumours (26 per cent) were well differentiated, 199 (59 per cent) were intermediately differentiated and 54 (16 per cent) were poorly differentiated. The one-year survival rates for the dogs with tumours of these three grades were significantly different (P = 0.0001), being 100 per cent, 92 per cent and 46 per cent, respectively. The median survival time for the dogs with poorly differentiated tumours was 278 days, significantly shorter than that for the dogs with either intermediately or well-differentiated tumours, which were both over 1300 days. Regrowth of the tumours was identified in 10 (19 per cent) of the dogs with poorly differentiated tumours, 12 (6 per cent) of the dogs with intermediately differentiated tumours and one of the dogs with well-differentiated tumours; only three of the tumours which regrew had initially had complete margins. The results suggest that wide surgical margins are not a prerequisite for a successful long-term outcome in dogs with well-differentiated cutaneous mast cell tumours.     

Canine Transmissible Venereal Tumour: Asessment of Mast Cell Numbers as Indicators of the Growth Phase

Mast cells are immune cells that are involved mainly in type 1 hypersensitivity reactions, and they have been implicated in tumour angiogenesis. In this study we assessed the presence of mast cell numbers and microvessel density during the progression and regression stages of natural spontaneous canine transmissible venereal tumours (CTVT). Mast cells were demonstrated by histochemical staining with toluidine blue, alcian blue and safranin O. Microvessel counts were demonstrated by immunohistochemical labelling with an antibody against the endothelial cell marker factor VIII. Mitotic cells, apoptotic cells and tumour infiltrating lymphocytes were counted from haematoxylin–eosin-stained sections. Tumour fibrosis was evaluated on Masson's trichome-stained sections. The results showed that progressing tumours had significantly higher mast cell counts and microvessel counts at the invasive edges of the tumours than did regressing tumours. In both the progressing and regressing tumours, microvessel counts were significantly positively correlated with mast cell counts. Regressing tumours had significantly higher mast cell counts of the whole tumour than progressing tumours. The results also showed that progressing tumours had significantly higher mitotic rate than regressing tumours, and fibrosis and apoptosis were significantly higher in regressing tumours than progressing tumours. There were no significant differences between the biochemical and haematological values of dogs with progressing and regressing tumours. These results suggests that mast cells play a role in CTVT progression probably by promoting vascularization at the invasion front during the progression phase, and that mast cell count could be used as one of the histological factors to indicate growth stage of CTVT.     

Canine mammary gland tumours; a histological continuum from benign to malignant; clinical and histopathological evidence*

This study describes the clinical and histopathological findings in dogs with mammary gland tumours, and compares the histopathological and clinical evidence consistent with progression from benign to malignant to human breast cancer epidemiology. Clinical and histopathological data on 90 female dogs with 236 tumours was included. Dogs with malignant tumours were significantly older than dogs with benign tumours (9.5 versus 8.5 years), P = 0.009. Malignant tumours were significantly larger than benign tumours (4.7 versus 2.1 cm), P = 0.0002. Sixty‐six percent had more than one tumour, and evidence of histological progression was noted with increasing tumour size. Dogs with malignant tumours were significantly more likely to develop new primary tumours than dogs with benign tumours, P = 0.015. These findings suggest that canine mammary tumours progress from benign to malignant; malignant tumours may be the end stage of a histological continuum with clinical and histopathological similarities to human breast carcinogenesis.     

A statistical assessment of the biological relationship between simultaneous canine mammary tumours

Simultaneous canine mammary tumours (CMTs) are frequently reported in the literature, but few studies have addressed their biological relationship in detail or performed statistical assessments. In this study, 269 canine mammary gland tumours from 216 dogs were categorized using an extended histopathological classification, where semiquantitative and binomial scales enumerated morphological parameters of the tumours. The classification facilitated a statistical study of the biological relationship between simultaneous within‐dog tumours. Seventy‐seven percent of the dogs had single tumours and 23% had simultaneous tumours. Sixty‐one percent of the neoplasias were benign, with complex adenoma as the most frequent diagnosis and 39% were malignant, with complex carcinoma as the most common malignancy. Simultaneous tumours within dogs more often had equal diagnoses and neoplastic level (benign or malignant) than would be expected by chance alone, as compared with random pairs of single tumours from different dogs. This statistically supported finding indicated the presence of a biological relationship between simultaneous tumours.     

A retrospective study of twenty-nine spinal tumours in the dog and cat

In a retrospective study of twenty-nine spinal tumours in dogs and cats approximately equal numbers of extradural and intradural tumours were found. The most prominent tumour type was the group of primary tumours of bone which included osteosarcomas, fibrosarcomas, hemangiosarcomas and multiple cartilagenous exostoses. Primary sarcomas of the spinal cord were the next most prominent type of tumour identified. A close clinicopathological correlation was found for tumour localization; however, intradural and extradural tumours could not be differentiated clinically. In comparison with extramedullary tumours which were evenly divided between acute and insidious onset, the majority of animals with intramedullary tumours had acute onset of neurological signs. In general, the intramedullary tumours had the shortest duration of clinical signs (1.7 weeks) whereas the extradural tumours had a mean duration of 3.4 weeks and intradural-extramedullary tumours had the longest mean duration (5.7 weeks). Contrast radiography was the most useful diagnostic aid. It confirmed the regional localization in twenty-two of twenty-four animals     

Nuclear Morphometry in Relation to Lymph Node Status in Canine Mammary Carcinomas

The assessment of nuclear area and nuclear shape by morphometric analysis, has been investigated in 40 canine mammary carcinomas in relation to their metastatic behaviour to regional lymph-nodes. The tumours were reviewed by two experienced pathologists blinded regarding their lymph-node status, and were classified according to the histogenetically based criteria suggested by Benjamin et al. (1999). Twenty of these tumours showed lymph-node metastases (node-positive), and the other twenty were node-negative. Node-positive tumours included 6 simple adenocarcinomas, 10 ductular carcinomas, 2 anaplastic carcinomas and 2 carcinomas in mixed tumours; node-negative tumours included 18 adenocarcinomas %96, 10 simple adenocarcinomas, 8 complex adenocarcinomas %96, and 2 carcinomas in mixed tumours. Node-positive tumours showed MNA and mean SDA values significantly higher (p<0.001) than node-negative carcinomas. Data of this study, seems to confirm the importance of an histogenetically based classification in canine mammary tumours, also suggesting that morphometry may increase our prognostic performances allowing a reproducible method for detecting individual tumours with higher metastatic potential.     

Effects of stage and number of tumours on prognosis of dogs with cutaneous mast cell tumours

Between 1997 and 1999, 280 dogs with mast cell tumours were identified, of which 59 (21 per cent) had multiple tumours. Follow-up data for survival analysis were available for 145 dogs with single tumours and 50 dogs with multiple tumours. There was no significant difference between the survival times of the two groups; the survival rates after 12 and 24 months were 88 per cent and 83 per cent, respectively, for the dogs with single tumours, and 86 per cent at both intervals for the dogs with multiple tumours. Eight of the dogs with single tumours had lymph node metastases (stage II disease) and these dogs had a median survival time of 431 days, whereas the 50 dogs with multiple tumours (classified as stage III disease) and the dogs with single tumours (classified as stage I disease) had not reached their median survival times. Golden retrievers appeared to be predisposed to developing multiple tumours in the population studied, with an odds ratio of 3.8. This study found no evidence that dogs with multiple tumours had different survival times than those with single tumours, although there was evidence that the presence of lymph node metastasis generally carried a poorer prognosis.     

Breed differences in the proportional morbidity of testicular tumours and distribution of histopathologic types in a population-based canine cancer registry

Histologically verified tumours submitted to the Norwegian Canine Cancer Register from 1990 to 1998 were studied (n=14,401). The proportion of testicular tumours (n=345) was 2.4%, and the breakdown of histological tumour diagnoses is presented. The frequency of the most common histopathological types was 33% interstitial (Leydig), 26.4% Sertoli and 33.9% seminomas/germ cell tumours. The average age at diagnosis was 10 years, but was significantly lower for Sertoli cell tumours (8.6 years) than for the other tumour types. Following a histopathological re-evaluation, 22.5% of the original tumor diagnoses were modified. Proportional morbidity ratios were calculated and individuals from the breeds Shetland sheepdog and Collie were five times more likely to have testicular tumours than the overall average for the registry. Breed differences in the distribution of histopathologic types were observed. Shetland sheepdog and Collie were most commonly diagnosed with Sertoli cell tumours, while all tumours from Norwegian elkhound in this material were seminomas.     

Malignant fibrous histiocytomas in dogs and cats: an immunohistochemical study.

Immunohistochemical staining was performed on seven canine and 10 feline soft tissue tumours histologically diagnosed as malignant fibrous histiocytomas (MFHs) or MFH-like tumours, and eight other histologically specified tumours (non-MFH). This was done to determine if commercially available antibodies that are used routinely in human diagnostic pathology for MFHs would express the same immunohistochemical patterns in canine and feline MFHs and MFH-like tumours. The antibodies were directed against human alpha 1-anti-trypsin (AT), human alpha 1-anti-chymotrypsin (ACT), human lysozyme, bovine S-100 protein and human desmin. AT did not show any immunoreactivity in the tissues investigated. Except for one MFH, all canine MFHs and other soft tissue tumours with a 'histiocytic' character stained for lysozyme and not for S-100. Six out of seven canine MFHs and MFH-like tumours stained positive for desmin as did most non-MFH sarcomas. Most of the canine and feline MFHs and MFH-like tumours were positive for ACT. These findings for ACT staining in canine and feline MFHs and MFH-like tumours are in agreement with the findings in human MFHs. The immunohistochemical results of canine MFHs and MFH-like tumours were different from those in cats. Feline MFHs differed from canine MFHs for both lysozyme and desmin staining.     

Congenital and hereditary tumours in domestic animals. 2. pigs. A review

The literature on congenital and hereditary tumours in pigs was reviewed. One hitherto unreported own case was added. Sporadic cases of congenital tumours included several types found in newborn piglets. Embryonic tumours (nephroblastoma, rhabdomyosarcoma) occurred either in newborn or in juvenile animals. Cardiac rhabdomyomas were provisionally classified as hamartomas. The hereditary tumours, melanomas and lymphomas, were reproducible by experimental matings. These tumours are particularly interesting as models to elucidate genetic and immunologic mechanisms of tumour diseases. Striking is the high degree of regression in porcine melanomas and the associated melanosis.     

Canine chemodectoma (extra-adrenal paragangliomas)-a comparative study

Sixty-seven cases of chemodectoma in dogs (fifty-nine aortic body, two glomus pulmonale, and six carotid body) were studied. The epidemiology, biological behaviour, and association with other tumours of canine and human chemodectoma were compared. The large number of sites of origin of human chemodectomas was not observed in the dog. The canine chemo-dectomas occurred as multiple tumours in 16% of the cases and were biologically similar to the human tumours. As with human chemodectomas, an association with endocrine tumours (such as phaeochromocyto-mas and thyroid neoplasms) was observed.
The aortic body tumours were the most common and occurred more frequently in males. A higher rate of metastasis (22%) and a higher frequency of multiple endocrine tumours in association with chemodectomas, not observed in the dog before, were seen. In contrast to the high frequency of interstitial cell tumours and a low frequency of Sertoli cell tumours noted in previous studies, a low frequency of interstitial cell tumours and a high frequency of Sertoli cell tumours were seen in this study. Similarly, a previously reported high frequency of haemangio-sarcoma was not observed in this series.
A significantly higher frequency of chemodectomas was seen in the brachiocephalic dogs (Boxers and Boston terriers). Chemodectomas in man have shown familial predispositions. However, in brachiocephalic dogs the high frequency of chemodectomas may be caused by their partially obstructed air passages, rather than by a genetic factor only.
A higher incidence of chemoreceptor-cell hyperplasia and chemo-     

Secondary bone tumours in the dog.

During a 2 1/2-year period 209 dogs with 218 malignant tumours were examined for skeletal metastases. There were 77 malignant tumours without visceral or skeletal metastases. Twenty-four (17%) of the 141 tumours with visceral metastases also had skeletal metastases. Ninety-eight of these tumours were of epithelial origin, and of these 21 (21.4%) had skeletal metastases. In 14 dogs, more than one bone had a metastatic tumour. The humerus, femur and vertebral column were most frequently involved. The lung was the most frequent site of metastatic tumours; then, in order, the liver, kidney and skeleton. The incidence of primary and secondary bone tumours was similar. Metastatic bone disease in the dog is far more common than is generally realized.     

Magnetic resonance imaging findings in 40 dogs with histologically confirmed intracranial tumours

Magnetic resonance (MR) images of 40 dogs with histologically confirmed primary and secondary intracranial tumours were reviewed. Forty-one tumours were diagnosed by means of MR imaging (MRI). MRI findings allowed diagnosis of a neoplastic lesion in 37/41 cases. Based on MRI features, differentiation between neoplastic and non-neoplastic lesions was possible in 24/27 (89%) primary brain tumours and in 13/14 (92%) secondary brain tumours. Diagnosis of tumour type based on MRI features was correct in 19/27 (70%) primary tumours and in 13/14 secondary tumours. The results of this study show that MRI is a good diagnostic imaging modality to detect neoplastic lesions and to diagnose tumour type in dogs. However, as some neoplasms show equivocal MRI features the technique has limitations in the detection of some intracranial tumours and in predicting tumour type.     

Decorin concentrations in canine normal and neoplastic mammary gland tissues

In the present study, the concentration of decorin in canine normal and neoplastic mammary gland tissues was examined to understand the potential role of decorin in development and progression of canine mammary tumours. The homogenates of 48 mammary gland tumours (10 benign and 38 malignant) and 10 samples of normal canine mammary gland tissue were used in the study. The presence and quantification of decorin was examined in the homogenates using Western blot and specific canine ELISA. Western blotting confirmed the presence of decorin both in the normal mammary gland tissues and in the mammary gland tumours. The concentration of decorin was significantly higher (p < .05) in the benign tumours and non-metastatic malignant tumours than in the normal mammary gland. The concentration of decorin was significantly lower (p < .05) in the malignant tumours with metastasis to regional lymph nodes compared with benign tumours and non-metastatic malignant tumours. No significant differences were found in the level of decorin between the benign and the non-metastatic malignant tumours. Both the histological type of malignant tumours and the histological grade did not significantly affect the concentration of decorin. These findings suggest that neoplastic transformation in the canine mammary gland leads to increase in the decorin protein synthesis. The reducing decorin concentration in canine malignant mammary tumours appears to facilitate the metastatic spread of these tumours.     

Radiological assessment of 50 cases of incisive or maxillary neoplasia in the dog

This paper reviews the radiological features of 50 canine incisive or maxillary tumours and discusses the value of radiological assessment in the diagnosis and staging of these tumours. The 50 tumours examined included 21 sarcomas, 15 carcinomas, three melanomas and an assortment of benign tumours of the oral cavity. There was not any site specificity for the different histological tumour types within the upper dental arcade, although fibrosarcomas had a tendency to be maxillary whereas the squamous cell carcinomas were equally distributed between the incisive and maxillary regions. Seventy-eight per cent of fibrosarcomas, 82 per cent of squamous cell carcinoma and all three melanomas examined showed radiological evidence of bone involvement. Radiographic changes were also seen in the benign tumours. The pattern of growth of tumours correlated with the radiological changes observed. Malignant tumours showed a tendency to irregular or aggressive bone loss whereas bone production predominated in the benign tumours.     

Expression of Endothelin‐1 and Endothelin Receptor A in Canine Ovarian Tumours

Ovarian tumours have a low incidence in bitch. Endothelin (ET‐1) and endothelin A receptor (ET‐A) are overexpressed in human ovarian cancer. Twenty canine ovarian tumours and five normal samples were first evaluated by western blotting and then immunohistochemically for ET‐1 and ET‐A expression. Seventeen out of twenty tumours were ET‐1 positive. Eight out of twenty tumours were ET‐A immunohistochemically positive. At molecular level both proteins were proven to be expressed in normal as well as in tumour samples. Our results show that ET‐1 and ET‐A are overexpressed in canine ovarian tumours, suggesting a potential role of these two molecules in canine ovarian carcinogenesis.     

Fine-needle aspiration biopsy of canine mammary gland tumours: a comparison between cytology and histopathology

In the current study, a total of 90 mammary neoplasms obtained from 55 female dogs were used to determine the accuracy of fine-needle aspiration cytology in the diagnosis of canine mammary tumours and to investigate the feasibility of this technique for the differentiation of simple tumours from complex or mixed tumours. Three aspirations were performed on each mammary gland mass using a 22-gauge needle attached to a 5-ml syringe before the mammary glands were surgically excised and submitted for histopathological examination. Twenty-five (27.7%) of 90 samples were classified as insufficient/inadequate for diagnosis. Of the remaining 65 samples, six (9.2%) were benign, 51 (78.5%) were malignant tumours and 8 (12.3%) were suspicious. Histopathological examination of the 90 specimens revealed five (5.6%) benign, 84 (93.3%) malignant and one (1.1%) non-neoplastic lesion. The diagnostic accuracy, sensitivity and specificity of cytologic examination for diagnosing malignancy were 96.5%, 96.2% and 100%, respectively. However, when inadequate (n = 25) and suspicious (n = 8) samples were included, the diagnostic accuracy and sensitivity decreased to 63.3% and 60.7%, respectively, but no change was observed in the specificity. Furthermore, it was not possible to differentiate simple tumours from complex and mixed tumours because spindle cells were seen in both 28% of the simple tumours and 39.3% of the complex or mix tumours. In conclusion, we believe that fine-needle aspiration cytology of canine mammary tumours is a valuable diagnostic tool, although our results indicated lower accuracy when inadequate samples were taken into consideration.     

Characterisation of the signalment, clinical and survival characteristics of 41 cats with mast cell neoplasia

Mast cell tumours (MCTs) are relatively common tumours of cats, and are the second most common cutaneous tumours in cats in the USA. While the primary splenic form of the disease is far less common, it is usually associated with more severe clinical signs. Signalment, clinical and survival characteristics of mast cell neoplasia were characterised in 41 cats. The most common tumour location was cutaneous/subcutaneous head and trunk. Stage 1a was the most common tumour stage at first diagnosis (n=20), followed by stage 4 (both stage 4a and stage 4b; n=10). Of 22 cats that underwent excisional biopsy, mast cell neoplasia recurred in four cats during the study period. Three of the 41 cats presented with simultaneous cutaneous and either splenic or lymph node tumours. A comparison between cats with only cutaneous tumours (n=30) and those with tumours involving the spleen or lymph nodes (n=11) showed longer survival times for the cutaneous-only group (P=0.031). Twelve of the 41 cats died of mast cell neoplasia during the study period. When a subgroup of cats with only cutaneous tumours (no lymph node or visceral involvement) were divided according to whether there were multiple (five or more) tumours (n=6) or a single tumour (n=19), cats with single tumours survived longer than those with multiple tumours (P=0.001). Solitary cutaneous feline MCTs without spread to the lymph nodes usually manifest as benign disease with a relatively protracted course. However, multiple cutaneous tumours, recurrent tumours and primary splenic disease should receive a guarded prognosis due to the relatively short median survival times associated with these forms of the disease.     

Immunohistochemical study of the expression of E-cadherin in canine mammary tumours

To investigate the possible role of E-cadherin in canine mammary tumours 20 benign and 40 malignant tumours were evaluated by immunohistochemistry in formalin-fixed paraffin wax-embedded samples. In all the benign tumours, E-cadherin was strongly expressed at the intercellular borders of epithelial cells, but it was less strongly expressed in 17 (43 per cent) of the malignant tumours. Furthermore, poorly differentiated carcinomas were less immunoreactive for E-cadherin than moderately and well differentiated carcinomas.