Canine Malignant Mammary Tumours I. Sarcomas

Forty-five canine mammary sarcomas that had metastasized were pooled from several institutes, studied, and classified. The classification was based on morphology and did not include any histogenetic interpretation. In addition, one case was studied by histochemical and electron microscopic methods. Canine mammary sarcomas often have multidifferentiation (bone, cartilage, and fat) which is not unusual in human mammary sarcomas. Sarcomas resembling (malignant) cystosarcoma phyllodes in women appear to be very rare in the dog. Canine fibrosarcomas had a morphological resemblance to ‘stromal’ sarcoma or ‘fibrosarcoma’ in the woman. Five sarcomas without infiltrative growth, anaplasia, or mitotic activity had metastasized. In dogs and women the lungs are often involved by metastases, but, unlike in the human, metastases in the regional lymph nodes are also relatively common in the dog. There is need for further studies on the histogenesis and biological behaviour of mammary sarcomas.