Mammography and ultrasound imaging of preinvasive and invasive canine spontaneous mammary cancer and their similarities to human breast cancer.

Understanding the evolution of proliferative breast disease such as atypical hyperplasia and carcinoma in situ is essential for clinical management of women diagnosed with these lesions. Therefore, an animal model that faithfully represents human breast disease in every aspect from spontaneity of dysplasia onset, histopathologic features, and genetics to clinical outcome is needed. Previously, we studied canine spontaneous atypical hyperplasia and ductal carcinoma in situ (low, intermediate, and high grade) and reported their similarities to human lesions in histopathologic and molecular features as well as prevalence. To further validate the resemblance of these lesions to humans, we examined their mammographic and sonographic characteristics in comparison with those of human's as well as the potential of the human Breast Imaging Reporting and Data System (BI-RADS) to predict canine disease. Nonlesional, benign, and malignant mammary glands of dogs presented to Sassari Veterinary Hospital were imaged using mammography and ultrasonography. The images where then analyzed and statistically correlated with histopathologic findings and to their similarities to humans. Our results showed that canine mammary preinvasive lesions, benign, and malignant tumors have mammographic abnormalities, including the presence, pattern, and distribution of macrocalcification and microcalcification, similar to their human counterparts. BI-RADS categorization is an accurate predictor of mammary malignancy in canine, with 90% sensitivity and 82.8% specificity. The similarities of mammographic images and the ability of BI-RADS to predict canine mammary malignances with high specificity and sensitivity further confirm and strengthen the value of dog as a model to study human breast premalignancies for the development of prognostic biomarkers.