Caracterização de tecidos mamários caninos normais e neoplásicos combinando técnicas de micro-fluorescência e espalhamento de Raios X

Abstract

Cancer is one of the main causes of deaths in the canine species, and 25% of these neoplasms occur in the mammary glands of these animals. Studies on canine breast cancer are not only relevant for this species, but also for human oncology. Canine breast tumors have histological and etiological similarities with human breast tissues, such as tumor development, hormonal dependence and metastatic pattern. Therefore, the study of canine breast tissues can serve as a model to understand the carcinogenic process of both species. The use of spectroscopic techniques, such as X-ray fluorescence and scattering, allows to obtain information about different biological tissues, and their application in the study of breast tumors can be useful to understand the relationship between tissue composition and the carcinogenic process. X-ray fluorescence is one of the most used techniques to determine the concentration of trace elements in breast tissues. The scattering of X-rays allows obtaining information on the effective atomic number (Zef). Thus, the objective of this work was to characterize normal and neoplastic canine breast tissues, combining X-ray micro-fluorescence (μ -XRF) and scattering techniques, to obtain information about the spatial distribution of chemical elements of the effective atomic number of the tissue matrix, respectively. This study analyzed nine samples of canine breast tissues (normal, benign and malignant) in the X-ray fluorescence beamline, at the National Synchrotron Light Laboratory – LNLS. Initially, the μ -XRF technique was applied using a polyenergetic beam to map the spatial distribution of chemical elements in breast tissues. Then, the X-ray scattering technique was used, with modification of the arrangement to use a monochromatic beam (12 keV). Selected points in the samples were measured in order to obtain ratio R/C and Zef values in these regions. The μ -XRF results were shown to be sensitive to variations in the spatial distribution of the different trace elements: S, Ca, Fe, Zn, Cu and Br, making it possible to create maps with these distributions, which were correlated with the different healthy and neoplastic regions of the breast tissues. The μ -XRF maps showed higher amounts of S and Ca in regions of acini and mammary ducts. Fe stood out in regions close to neoplasms and blood vessels in the samples. Zn and Cu were distributed in a similar way throughout the tissues, except for regions of blood vessels, which presented greater intensity of Zn. As for the behavior for the ratio R/C and Zef, there was agreement with the studies found in the literature, with low values in regions of the less glandular and increasing in fibroglandular and tumoral regions. Finally, it is observed that the combination of 𝜇-XRF and X-ray scattering techniques allowsf obtaining complementary information in the study of normal and neoplastic canine breast tissues.