Comparative evaluation of collagen modifications in breast cancer in human and canine carcinomas.

New diagnostic and therapeutic approaches have been increasingly demanded due to the high morbidity and mortality associated with breast cancer. Recently, changes in the collagen fibres in mammary neoplasms have been shown to provide information that can be helpful for more accurate diagnosis. We aimed to conduct a comparative analysis of the tumour stroma in human and canine mammary neoplasms to assess the relationship between collagen modifications and the behaviour of carcinomas in both species, by multiphoton microscopy. We present a retrospective study of 70 cases of human mammary tumour and 74 cases of canine mammary tumour. We analysed sections stained with haematoxylin and eosin from 1,200 representative areas of normal mammary tissue, fibroadenoma, grade I invasive carcinoma, grade III invasive carcinoma and invasive micropapillary carcinoma in human species and 1,304 representative areas of normal mammary tissue, benign mixed tumour, mixed carcinoma, carcinosarcoma, invasive micropapillary carcinoma and solid carcinoma in canine species. We obtained that both human and canine mammary carcinomas present lower density of collagen fibres, higher density of cells and the collagen fibres are more aligned than in normal tissue. For human mammary carcinomas, the collagen fibres are more linear as compared to normal tissue. In addition, we demonstrated that the carcinomas with unfavourable prognosis present shorter collagen fibres, and these collagen changes correlate with the clinical and pathological data in human and canine species. For dogs, there is a correlation between the mean fibre length with the specific survival times. Thus, we demonstrate that dogs provide an excellent comparative perspective for studying how changes in the tumour stroma affect patient survival.