A case of breast cancer detected by a pet dog

described the detection of a malignant melanoma by a pet dog. A 44-year-old woman’s border collie/Doberman mix sniffed and bit at a specific mole on her leg while ignoring other moles and lesions, prompting medical attention that led to the diagnosis. Church and Williams2 later reported a patient whose Labrador retriever doggedly sniffed at a lesion on the patient’s left thigh, eventually leading to a diagnosis of basal cell carcinoma. In both cases the dogs detected the lesions through the patients’ clothing and ceased interest once the lesions were excised. Here we report a case of breast cancer that was detected after similar peculiar behavior in a pet dog.