Chronic encysted abscess, so closely simulates various tumors in this situation, as to render a diagnosis in some cases very difficult during life. It usually commences as a result of pregnancy; sometimes as a consequence of lacteal inflammation; but usually without any injury or other direct local cause. An indolent, indurated swelling forms, and this may gradually soften in the centre, although fluctuation may for a long time be very indistinct, and even absent, owing to the thick wall of plastic matter that is thrown around the collection of pus. It is not unfrequently attended with retraction of the nipple. Syphilitic ulcers are also found affecting the nipple; while eczematous and erysipelatous inflammation in this situation are of frequent occurrence. Morbid Growths. The mammæ are frequently the seat of adventitious growths, presenting the characters of non-malignant and malignant formations. The most common of the benignant tumors is, perhaps, the =Adenoid Tumor or Adenocele=. This is most frequently met with in young women under thirty years of age, seldom commencing at a later period than forty. It may remain stationary for years, or it may slowly increase or grow very rapidly to a great size. It has frequently been mistaken for cancer, but the otherwise good health of the patient, the mobility of the mass, the absence of all implication of the skin or glands, the want of hardness and its circumscribed character, are points of diagnostic value. On removal, it appears irregularly lobulated, is encapsulated, and its cut surface has a bluish or grayish-white color, which, on exposure to the air, assumes a rosy tint. On pressure, drops of thick, creamy fluid will often exude. According to Birkett, the microscope shows it to consist of imperfectly developed hypertrophy of the glandular tissue, the terminal cells of which are filled with epithelial scales. This tumor sometimes simulates malignant disease by its extreme rapidity of growth, especially where it developes later in life. It then, after section, presents a lobulated, glistening appearance, somewhat resembling a mass of rice or sago jelly, often having cysts interspersed throughout its substance containing fluid or semi-solid glandular tissue. In rare cases, the adenocele may return, even after extirpation of the entire mammary gland. =Cystic Tumors.= These may occur as the unilocular cyst, or as the cysto-sarcomatous tumor. _Unilocular cysts_ usually occur as a small, thin sac, of about the size of a filbert, containing a clear, serous fluid, imbedded in the glandular structure of the breast, and movable under the skin. As they increase in size or become multiple, their contents may assume a greenish-brown or blackish tinge from effused blood. According to Brodie, they are originally formed by a dilatation of the lactiferous tubes.