B-mode and Color Doppler ultrasonographic examination of mammary tumors in the bitch

Introduction and aim. Mammary neoplasia are the most common tumors in the bitch and about 50% are malignant (1, 2). The classification of tumor is important for the prognosis, but few non-invasive and reliable diagnostic procedures are available for this aim. In human medicine ultrasonographic examination of mammary masses is widely used (3). Besides B-mode ultrasound aimed to the structural evaluation of the neoplasia (4), Doppler ultrasound and flow indices, i.e. Pulsatility Index (PI), Resistive Index (RI), Maximum Velocity (Vmax) and Mean Velocity (Vmean), are applied to accurately evaluate the vascularization of the tumor (3, 5). The aim of this study was to investigate the correlation between ultrasonographic findings (B-mode and Color Doppler indices) and histological patterns of canine mammary tumors. Materials and methods. Eight not spayed and one spayed bitches of different breeds, aged between 6.5 and 10 years, were evaluated for mammary tumors (total of 16 mammary nodules). Patients underwent an ultrasonographic examination of mammary nodules immediately before surgery. B-mode examination included size, texture, echogenicity, edges, artifacts of the mammary masses, and through Color Doppler the flow indices (PI, RI, Vmax and Vmean), the number of vessels (scoring system from 0= no vessels to 3= >5 vessels), their position (central, peripheral or extratumoral) and shape were recorded. After mastectomy, histological evaluation of each tumor was compared to ultrasonographic findings. Statistical analyses were performed with Fisher test and Median test for clinical and B-mode data, and with Kruskal-Wallis test for eco-Doppler data. The Receiver Operating Characteristic (ROC) curve was used to calculate the Vmean cut-off value. All calculations were performed using MedCalc Software. Results. Malignant neoplasms (adenocarcinoma) were 62.5% of the total tumors and their average size was higher than that of benign neoplasia (mean value 1.98 cm x 1.72 cm vs. 1.2 cm x 0.8 cm, respectively). Undefined edges and patchy textures were often observed in malignant tumors, but no significant differences were found between the two groups. The presence of cystic areas was significantly higher (p<0.01) in malignant than in benign tumors. The latter, compared to malignant tumors, showed more linear vessels and lower, although not significant, vascular score, RI and PI. However, flow indices as Vmax and Vmean were significantly higher (p<0.05 and p<0.001) in malignant than in benign neoplasms and the cut-off value of Vmean was 8.28 cm/sec, with a sensitivity of 73.9% and specificity of 100%. Moreover its positive and negative predictive value resulted 100% and 60%, respectively. Conclusions: B-mode and Color Doppler ultrasonographic examinations might be helpful diagnostic tests for the assessment of mammary tumors. In particular, cystic areas and high value of Vmax and Vmean are significantly correlated with malignant neoplasms and the cut-off value for Vmean could be clinically useful for differential diagnosis between benign and malignant tumors.