Estudo comparativo da arquitetura e orientação das fibras colágenas em neoplasias mamárias caninas por Geração de Segundo Harmônico e Microscopia por Absorção de dois Fótons

Abstract

Breast cancer has of great importance for public health due to the high morbidity and mortality related for disease. Canine mammary neoplasms have great epidemiological, clinical, biological and genetic similarities and, therefore, they have been considered good models for the study of breast cancer in women. It is known that the extracellular matrix plays an important role during tumor progress and, in the process, the collagen fibers become more organized and aligned. It is believed that this event is associated with invasions and the capture of tumors, which is important in the appearance of metastases. Thus, the aim of this study was to correlate the changes collagen fibers in the main subtypes of mammary carcinomas of dogs with the tumoral behavior and clinical-pathological characteristics. For this, a retrospective study was carried out with 45 cases of canine mammary neoplasm in which 05 histological subtypes were selected - benign mixed tumor, carcinoma in mixed tumor, carcinosarcoma, micropapillary carcinoma and solid carcinoma; and 12 samples normal mammary gland. Microscopy analyzes were performed through second harmonic generation and absorption of two photons. Measurements were taken in 950 different regions using the described methodology. Six parameters were selected - SHG anisotropy, local SHG anisotropy, no. fibres, mean fibre length, fibre coverage area and cell coverage area - for comparison between histological types and normal breast. The same parameters were used for comparisons between normal mammary regions and benign regions, malignant in situ and malignant invasive regions in the carcinoma in mixed tumor, for the evaluation of collagen fibers during tumor progression. Subsequently, correlations were carriet out between the analysed parameters and the clinical-pathological data. The data showed that in neoplastic tissues the collagen fibers are more organized and aligned in relation to normal tissues. It was possible to observe a greater collagen organization as the tumor progression. However, when comparing the length of collagen fibers between the different histological types of carcinomas, was observed that in more aggressive tumors the fibres smaller in relation to less aggressive tumors, possibly due to the rupture of the fibres by the tumor cells for infiltration of the surrounding tissue. The mean fibre length showed a correlation with canine’s survival and with histological subtype, histological grading and cell proliferation of the mammary carcinomas evaluated. Thus, the evaluation of collagen by the second harmonic generation technique allowed to demonstrate differences in the alignment of collagen fibers between neoplasms and the normal mammary gland, during tumor progression. It also made it possible to assess differences between more aggressive tumors with an unfavorable prognosis and less aggressive carcinomas. In addition, it was possible to establish a cutoff point for the mean fibre length when they are correlated with the survival of bitches, suggesting that microscopy by second harmonic generation can be used as a test with prognostic value for mammary cancer in bitches.