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A preliminary classification of 130 canine mammary adenocarcinomas, 76 solid carcinomas, and nine spindle cell carcinomas, together with several subtypes, was constructed from pooled, selected (metastasized) material. Each tumour in this series was classified by subjective assessment of its quantitatively predominant histological picture. Many adenocarcinomas and solid carcinomas of simple type were infiltrative, and lymphatic permeation was often found. The complex types of adenocarcinomas and of solid carcinomas were expansive, and lymphatic permeation was rare. Some metastasized adenocarcinomas were well differentiated. The clinical signs, distribution of metastases and some preliminary data on the times of survival of dogs with various types of carcinomas are discussed.

Sixty-four metastasized canine malignant mammary tumors were studied. The most important types of canine mammary cancer are discussed. Mammary squamous cell carcinomas of different types are found more frequently in the dog than in man. Mucinous carcinoma, a very rare type in the dog, seems to be more malignant than its counterpart in man. Anaplastic carcinoma in the dog is a very malignant diffusely infiltrating and extensively metastasizing cancer. The malignant mixed tumors, although showing many resemblances to complex carcinomas, are discussed here as a separate group. Both categories of tumors seem to be extremely rare in man. Simple carcinomas are highly infiltrating tumors metastasizing frequently to the regional nodes and lungs; survival time is short. Complex carcinomas are generally less invasive than simple carcinomas, and lymphatic permeation is also less frequent, resulting in a lower percentage of affected nodes; the median survival time is relatively long. The sarcomas, growing mostly in an expansive way, tend to spread mainly to the lungs; survival time is short.

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.

1. The behaviour of various types of cortical bone graft has been studied in rabbits by histological and injection techniques.2. The results suggest that penetration of the graft by blood vessels plays an important part in the incorporation of autogenous and homogenous grafts.3. Autogenous and homogenous grafts are both incorporated–the latter more slowly than the former–but heterogenous grafts are rejected. The reasons for this rejection are discussed.