Fibrosarcoma affecting the mammary gland of a cow.

A highly malignant fibrosarcoma which arose in or close to the mammary gland of a 12 year old Ayrshire cow, with metastases in local lymph nodes, lungs, liver, kidney and adrenal glands has been described. The tumors were densely cellular and consisted of interweaving bands of fusiform cells with a high mitotic index. Infiltration of normal tissues and invasion of blood vessels were characteristic features. Ultrastructural study of the cells revealed mesenchymal cells with abundance of rough endoplasmic reticulum and cytoplasmic vesicles and they were closely invested with collagen fibers.