Mapeamento de tumores mamários caninos e tecidos adjacentes por meio da microdifração de raios X

Abstract

Canine mammary tumors have been suggested as a model to study humans due to its high incidence rates, exposure to the same environmental factors and because both present similar development characteristics. Therefore, it is possible to assume that structural changes found in canine tumor monitoring can be extended to human cancer. Wide-angle X-ray scattering (WAXS) provides information regarding the molecular organization of tissues, which can increase the understanding of cancer infiltration and thus aid in its diagnosis and treatment. The purpose of this study was to map the structural changes in canine mammary tissues surrounding benign and malign tumors, using X-ray microdiffraction. Five samples were investigated, including simple and polycystic adenoma, solid carcinoma and two adenocarcinomas. These were stored in formalin at room temperature and covered with a thin layer of Kapton film during the experiment. After measuring five points in each sample, these were lyophilized, in order to study the influence of water in the scattering process. Measurements were carried out in a D8 Discover Bruker Diffractometer, with a microfocus source (Ka = 8.04 keV), and a 2D Vantec 500 detector. The momentum transfer ranged from 5.8 nm-1 to 41.3 nm-1, with steps of 0.005º for samples fixed in formalin, and from 8.7 nm-1 to 39.1 nm-1, with 0.01º steps for the lyophilized ones, both with 600 seconds of exposition per step. Correction factors related to self-attenuation in the sample and external contributions were applied. Regions of glandular tissue peaked at q = 19.8 nm-1, which is related to the distance between oxygen particles in neighboring water molecules. A less intense peak around q = 30.0 nm-1 is also noticeable, both in glandular and adipose tissues, and can be related either to the connection of hydroxyl groups between water molecules or to the harmonic scattering of the fatty acids’ peak. Adipose tissue presented a narrower peak at q = 13.9 nm-1, consistent with the fatty acids chain. In conclusion, the analyzed spots presented very different profiles, proving how heterogeneous the tumoral sample is. By analyzing the lyophilized samples, it is observed that points containing more fibroglandular tissue lose more hydric content than others. In these samples the peak q = 19.8 nm-1 was supressed, reinforcing its link to water molecules.