Ahtrcrct. Sixty-four metastasized canine malignant mammary tiiniors 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, s e e m to be more malignant than its counterpart in nian. 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 gro~ip. Both categories of tumors seem to be extremely rare in nian. Simple carcinomas arc 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.Canine maminary adenocarcinonias, solid carcinomas, and spindle cell carcinomas have been discussed in a previous paper [9]. The present paper describes three special types of maminary carcinoma (squanious cell, mucinous, and anaplastic types) that had proved their malignant nature by metastasizing; a group of malignant mixed tumors that had metastasized is also discussed. The macroscopic and microscopic appearances of all tumor

This paper describes a case of a congenital vascular malformation in the skin of a colt. The lesion arose at the coronary border of the right hind leg. The microscopic structure of a biopsy suggested that the lesion, consisting of multiple foci of closely-packed convoluted small vessels in the dermis, represented a marked exaggeration of glomi which normally occur in considerable numbers in this region of the skin. On the basis of the clinical, macroscopic and histological findings, this lesion was considered to be an hamartoma, rather than a true tumour, and was therefore termed a congenital vascular naevus. The foal is remaining under observation to determine the eventual outcome of the lesion.