Tumours of the udder have been little studied in the larger domestic animals, the reason being that immediately animals cease to yield milk they are fattened and despatched to the butcher. Clinically, therefore, these tumours are not of great practical importance.
Without entering into general considerations of a pathological anatomical character, by which different varieties of these tumours are differentiated, we may say that they assume one of three different forms. The first is sharply circumscribed, of clearly defined shape, and easily separated from neighbouring tissues, to which it adheres but slightly. Such tumours are benign, and have no tendency to return after removal.
The second is ill-defined, very adherent, and appears to infiltrate the surrounding tissue. It is malignant in character, is often impossible to completely remove, returns after extirpation, and infects neighbouring lymphatic glands.
Between these two varieties may be placed a third, occupying an intermediate position as regards both its characteristics and gravity.
Practically a knowledge of the above facts is a sufficient guide in dealing with lesions of this character.
Canalicular Papillomata.—There exists another variety of tumours which is of much more frequent occurrence, and which is apt to cause mistakes. This variety consists of inter-canalicular papillomata.
These show no sign of their existence on external examination of the diseased udder, and can be diagnosed only by reasoning based on the signs observed.
They are of very small size, and grow from the internal wall of the galactophorous sinus or excretory canal. They increase in length, finally extending for some distance along the sinus, where they remain unrecognised until some external manifestation arouses suspicion as to their existence.
Under the mechanical contraction due to milking they easily become excoriated, and their existence is then suggested almost solely by the fact that the milk is tinted with blood, for palpation of the udder very seldom gives more than negative results.
The diagnosis is always doubtful. The prognosis is grave, because it is impossible to remove the tumour, which is often deeply placed within the udder. There is no curative treatment.