Cell proliferation and differentiation of the canine mammary mixed tumor

Dog is the most tumor frequent species in the veterinary field. Mammary tumor is one of the most frequent tumor in the dog next to the skin tumor. In the canine mammary tumors, half of them are said to be mixed tumor. Mixed tumor has been paid special attention of the morphologist since long time ago because of its characteristic features, i. e. formation of cartilage and bone in the mammary tumor tissue. However, its morphogenesis has not been com-pletely understood yet. Recent veterinary onco~ogists regard the canine mixed tumor as a mammary tumor with mucoid, chondroid or osteoid tissue together with acinar or ductal structures. These tissues are considered t