Background: Although several histopathological and clinical features of canine mammary gland tumours have been widely studied from a prognostic standpoint, considerable variations in tumour individual biologic behaviour difficult the definition of accurate prognostic factors. It has been suggested that the malignant behaviour of tumours is the end result of several alterations in cellular physiology that culminate in tumour growth and spread. Accordingly, the aim of this study was to determine, using a multivariable model, the independent prognostic value of several immunohistochemically detected tumour-associated molecules, such as MMP-9 and uPA in stromal cells and Ki-67, TIMP-2 and VEGF in cancer cells. Results: Eighty-five female dogs affected by spontaneous malignant mammary neoplasias were followed up for a 2-year post-operative period. In univariate analysis, tumour characteristics such as size, mode of growth, regional lymph node metastases, tumour cell MIB-1 LI and MMP-9 and uPA expressions in tumour-adjacent fibroblasts, were associated with both survival and disease-free intervals. Histological type and grade were related with overall survival while VEGF and TIMP-2 were not significantly associated with none of the outcome parameters. In multivariable analysis, only a MIB-1 labelling index higher than 40% and a stromal expression of MMP-9 higher than 50% retained significant relationships with poor overall and disease-free survival. Conclusions: The results of this study indicate that MMP-9 and Ki-67 are independent prognostic markers of canine malignant mammary tumours. Furthermore, the high stromal expressions of uPA and MMP-9 in aggressive tumours suggest that these molecules are potential therapeutic targets in the post-operative treatment of canine mammary cancer.

Cutaneous mast cell tumours are one of the most common neoplasms in dogs and show a highly variable biologic behaviour. Several prognosis tools have been proposed for canine mast cell tumours, including histological grading and cell proliferation markers. CD117 is a receptor tyrosine kinase thought to play a key role in human and canine mast cell neoplasms. Normal (membrane-associated) and aberrant (cytoplasmic, focal or diffuse) CD117 immunoexpression patterns have been identified in canine mast cell tumours. Cytoplasmic CD117 expression has been found to correlate with higher histological grade and with a worsened post-surgical prognosis. This study addresses the role of CD117 in canine mast cell tumours by studying the correlations between CD117 immunoexpression patterns, two proliferation markers (Ki67 and AgNORs) histological grade, and several other pathological variables.

A series of 131 local and regional lymph nodes from 40 dogs with malignant mammary tumours were evaluated by staining with haematoxylin and eosin and immunohistochemically for antibodies to pancytokeratin ( AE1/AE3 ) and cytokeratin 14. The immunohistochemical tests detected occult micrometastases in 9·2 per cent of the lymph nodes that were negative by haematoxylin and eosin staining. Under the modified TNM classification of canine mammary tumours, these results raised the clinical stage of 12·5 per cent of the affected dogs. However, if the latest TNM classification of human breast cancer had been applied, none of the animals would have been reclassified.

There is long‐standing evidence that male and female rat livers differ in enzyme activity. More recently, differences in gene expression profiling have also been found to exist; however, it is still unclear whether there is morphological expression of male/female differences in the normal liver. Such differences could help to explain features seen at the pathological level, such as the greater regenerative potential generally attributed to the female liver. In this paper, hepatocytes (HEP), Kupffer cells (KC) and hepatic stellate cells (HSC) of male and female rats were examined to investigate hypothesised differences in number, volume and spatial co‐localisation of these cell types. Immunohistochemistry and design‐based stereology were used to estimate total numbers, numbers per gram and mean cell volumes. The position of HSC within lobules (periportal vs. centrilobular) and their spatial proximity to KC was also assessed. In addition, flow cytometry was used to investigate the liver ploidy. In the case of HEP and KC, differences in the measured cell parameters were observed between male and female specimens; however, no such differences were detected for HSC. Female samples contained a higher number of HEP per gram, with more binucleate cells. The HEP nuclei were smaller in females, which was coincident with more abundant diploid particles in these animals. The female liver also had a greater number of KC per gram, with a lower percentage of KC in the vicinity of HSC compared with males. In this study, we document hitherto unknown morphological sexual dimorphism in the rat liver, namely in HEP and KC. These differences may account for the higher regenerative potential of the female liver and lend weight to the argument for considering the rat liver as a sexually dimorphic organ.

Background: Sialyl Lewis x (sLe^x) antigen is a carbohydrate antigen that is considered not only a marker for cancer but also implicated functionally in the malignant behaviour of cancer cells. Overexpression of sLe^x is associated with enhanced progression and metastases of many types of cancer including those of the mammary gland. Canine mammary tumours can invade and give rise to metastases via either lymphatic or blood vessels. E-Cadherin is specifically involved in epithelial cell-to-cell adhesion. In cancer, E-Cadherin underexpression is one of the alterations that characterizes the invasive phenotype and is considered an invasion/tumour suppressor gene. Partial or complete loss of E-Cadherin expression correlates with poor prognosis in canine malignant mammary cancer. The aim of this study was to analyse the sLe^x expression in canine malignant mammary tumours and to evaluate if the presence of sLe^x correlates with the expression of E-Cadherin and with clinicopathological features. Methods: Fifty-three cases of canine mammary carcinomas were analysed immunohistochemically using monoclonal antibodies against sLe^x (IgM) and E-Cadherin (IgG). The clinicopathological data were then assessed to determine whether there was a correlation with sLe^x tumour expression. Double labelled immunofluorescence staining was performed to analyse the combined expression of sLe^x and E-Cadherin. Results: sLe^x expression was consistently demonstrated in all cases of canine mammary carcinomas with different levels of expression. We found a significant relationship between the levels of sLe^x expression and the presence of lymph node metastases. We also demonstrated that when E-Cadherin expression was increased sLe^x was reduced and vice-versa. The combined analysis of both adhesion molecules revealed an inverse relationship. Conclusion: In the present study we demonstrate the importance of sLe^x in the malignant phenotype of canine malignant mammary tumours. Our results support the use of sLe^x as a prognostic tumour marker in canine mammary carcinomas. Furthermore, we showed that sLe^x and E-Cadherin expression were inversely correlated. Future studies are warranted to clarify the molecular mechanism underlying the relation between sLe^x and E-Cadherin in canine mammary carcinoma cells which represents an important comparative model to woman breast cancer.