Morphometric Parameters as the New Differentiation Criteria of Histological Types of Mammary Gland Tumour in Dogs

Introduction . Canine mammary gland tumour is a widespread pathology registered in 20–30% of all the cases admitted to the veterinary clinics. Malignant mammary gland neoplasms cause the specific structural changes in the tissue, with the specific morphological transformations of the cellular, nuclear, parenchymatous-stromal and vascular components. However, currently, in the world there are no extensive and in-depth studies in this field, therefore the laboratory diagnostics of tumours using the examination of the morphometric parameters is difficult or impossible. The aim of the present research is to establish the significant morphometric parameters enabling differentiation of the histological types of canine mammary gland tumours in the course of diagnostics. Materials and Methods . The research was conducted from 2022 to 2023 and based on investigation of the excisional biopsy specimens (n=15) obtained after unilateral mastectomy in dogs. The review specimens demonstrated the signs of three main histological types of tumour, which formed the respective groups: tubular (n=5), medullary (n=5) and solid (n=5). The sample of the studied histological types represented by three groups was subdivided into the main categories of morphometric parameters – cellular and nuclear (tubular (n=995), medullary (n=995), solid (n=995)), parenchymatousstromal (tubular (n=154), medullary (n=154), solid (n=154)) and vascular (tubular (n=1233), medullary (n=1233), solid (n=1233)). To establish the statistically significant differences among the studied parameters, a single-factor analysis of variance and its non-parametric analogue — the Kruskal-Wallis test, were used. The obtained results were analysed by interpretation of the calculated F-test. Results . The area of the medullary carcinoma nuclei was larger compared to the tubular (p<0.01) and solid (p=0.000), the size of tubular carcinoma nuclei was larger than that of the solid (p=0.000). The highest nuclear-cytoplasmic ratio was determined in medullary carcinoma (p=0.000), the lowest — in solid carcinoma (p=0.000). The diameter of solid carcinoma vessels exceeded that of tubular (p=0.000) and medullary (p=0.000), and the diameter of tubular carcinoma vessels was slightly larger than that of medullary (p=0.001). Discussion and Conclusion . All the studied histological types of tumours had statistically significant differences, which makes it possible to differentiate them when examining the morphometric parameters of the tissue. However, not all of the formed categories of morphometric parameters had demonstrated the statistical significance and require further study. The parenchymatous-stromal category of morphometric parameters had the least efficient differential properties. The cellular and nuclear category showed the greatest differential value due to availability of the specific differences distinguishable among all other tumour types. The most significant morphometric parameters in this group were the area of the nucleus and the nuclear-cytoplasmic ratio. The vascular category of parameters turned out to be highly specific and, therefore, the second diagnostically significant category of morphometric parameters. In this category of parameters, the vessel diameter proved to be of the greatest diagnostic value.