According to what has been stated in the general sectionof this work, we have, in cancer, an aberrant growth of epithelium as the foundation process. In the more usual or ordinary cancers the process begins in the glandular acini. At the growing margin of the tumour the epithelium of the acini is seen to be proliferating, so that the acini are distended and enlarged. Along with the new-formation of epithelium in the acini there is a formation of round cells in the connective tissue around. The epithelium of the acini next grows through the basement membrane, forming penetrating processes, and the round cells develop connective tissue which frequently causes great contraction of the tumour (Scirrhus). It is as if the epithelium, growing outwards, acted as an irritant, causing inflammatory new-formation in the interstitial tissue of the gland. Whera the case is very chronic the connective-tissue formation may be very pronounced, but when more acute the epithelial elements preponderate.

A special group of cases has been distinguished by Thin under the name of Duct cancer. The peculiarity of this class is that the lesion begins in the large ducts near the nipple, and extends from these, first to the smaller ducts and then to the glandular parenchyma. The ducts, larger and smaller, are distended with growing epithelium. The tumour in the gland itself has the characters of ordinary cancer, so that the name duct cancer refers chiefly to the mode of invasion.

Paget's disease or Eczema of the nipple, also called Darier's disease, frequently precedes or accompanies the occurrence of cancer of the mamma, and the form of cancer is Duct cancer. This association is important, from the fact that in Paget's disease coccidia are stated to occur in the epithelium. Eczema, as indicated in the section on Diseases of the Skin, is an inflammation of the skin, in which both the epidermis and the superficial layers of the cutis are engaged. The superficial or papillary region of the skin may be replaced almost entirely by round cells, and the condition is somewhat like that of a granulating wound. The epithelium of the surface takes little part in the process, and it may be lost, so that the granulation tissue is exposed. The connection of this disease with cancer is not perfectly clear. Perhaps the most probable suggestion is that the causative agent begins by acting on the surface structures, and afterwards extends by the nipple into the ducts, producing duct cancer. A further extension into the gland leads to the lesions of ordinary cancer. According to Thin, however, the cancer of the ducts is present from the first, but is concealed by the eczema.

Section of cartilaginous part of a tumour of mamma which contained besides spindle celled and fibrous tissue, x 200.

Fig. 470. - Section of cartilaginous part of a tumour of mamma which contained besides spindle-celled and fibrous tissue, x 200.

Section of cancer of mamma from a recent nodule.

Fig. 471. - Section of cancer of mamma from a recent nodule. Epithelial cells in spaces formed by connective tissue; these are sometimes in single rows, and by multiplication form larger masses, x 200. (Cornil and Ranvier).

In its atypical growth the glandular epithelium sends its processes into the Lymphatic spaces of the connective tissue. There is commonly a further extension to the lymphatics outside the gland. These are sometimes seen distended by cancerous growth, but even without this obvious involvement the infection has often spread to the axillary glands. These may be but slightly enlarged and yet the seat of distinct cancerous new-formation.

Forms Of Cancer Of The Mamma

The various forms are not absolutely separable one from the other. They all originate in the glandular structures, and they are distinguishable chiefly by variations in the proportion of cells and stroma, and also by the transformations of these.

(A) Fibrous Cancer. Scirrhus

This is the commonest form, constituting about 95.5 per cent, of the cases (Gross). The epithelial masses form elongated processes (see under Cancer) in the midst of an excessive stroma composed of fibrous tissue. The epithelial cells are often atrophied so that in some parts of the tumour there is little beyond dense connective tissue. The cancer commonly forms a limited infiltration of a part of the gland rather than a proper tumour, and as the tissue contracts there is commonly an actual diminution of bulk with great induration. The gland is distorted and puckered towards the affected part.

Very often the disease is continuous with the nipple, and by the dragging of the tissue the nipple is drawn in, sometimes even forming an umbilicated depression. The tumour is very irregular in its extension in the gland, and it very often happens that in the midst of hard scirrhous tissue some Adipose tissue appears. In like manner pieces of the gland tissue may crop up amidst the contracting tumour.

The skin is frequently involved in the cancer. The cancer reaching the skin sends narrow processes of epithelium amongst the connective tissue, which forms the cutis vera, so as to produce an infiltration and thickening of this structure. When the skin is largely replaced by the cancerous tissue Ulceration usually occurs, generally beginning about the site of the nipple and areola. The ulcer, at first a mere excoriation, is liable to become crater-shaped with dense prominent walls. Sometimes after formation of the ulcer the growth of the cancer becomes more rapid.

When the mamma is cut into, either the whole gland or a portion of it is seen to be occupied by a dense mass of a greyish colour on the cut surface. It is very hard to cut, and the cut surface is commonly concave, the elasticity of the dense connective tissue producing retraction. In the general grey basis there are various whitish or yellowish pieces which represent the remains of mammary or adipose tissue, or the cancerous epithelium in a state of fatty degeneration. If the cut surface be scraped a thickish juice is obtained, which microscopic examination shows to be composed of epithelial cells and their debris. Many of the cells are large and well-formed though variously shaped, while some may contain enclosures which, under the newer views, are regarded as parasitic. The cells have often double nuclei (see Fig. 472). There are also free nuclei which have escaped from cells as a result of mechanical interference in the process of preparing the specimen. Many of the cells present fatty degeneration; in fact, very often nearly all contain fatty granules, and there are some completely degenerated, showing nothing but an aggregation of fat drops like the compound granular corpuscle.

The secondary tumours in the lymphatic glands also show an excessive development of fibrous stroma, which, however, usually forms a more distinct meshwork than that in the mamma, while the epithelial cells form more definite groups.

(B) Soft Or Acute Cancer

This forms the opposite extreme to scirrhus, and there are all intervening grades. In the soft cancer we have a bulky tumour of soft consistence and rapid growth. There is a well-formed alveolar stroma, and the cells are somewhat loosely contained in it. The tumour involves neighbouring tissues, very readily infiltrating the skin, subjacent muscle, and even the osseous ribs and the pleura. This form is sometimes present simultaneously in both breasts. On section the tumour presents a grey brain-like appearance. The juice furnishes numerous cells,, which are arranged in groups. As the tumour commonly extends to the skin, we may have ulcers with fungating prominence of the tissue. The lymphatic glands are early affected, and they also may ulcerate.

Many large tumours of the mamma of comparatively rapid growth do not correspond with the description either of the soft or medullary cancer or of scirrhus. In their minute structure they are more like scirrhus, and perhaps may be designated Acute scirrhus. They have a remarkably fine fibrous stroma, but it forms distinct meshes in which the epithelial masses are contained with considerable regularity. The cancer cells are large and essentially like those in scirrhus. The tumour as a whole also is hard, this depending on the abundance and density of the stroma.

Cells in the juice scraped from a scirrhus of mamma.

Fig. 472. - Cells in the juice scraped from a scirrhus of mamma. They are of very irregular shape. Most of them contain several nuclei and some daughter cells, x 200.

(C) Colloid Cancer

As compared with scirrhus, this is a rare form of tumour, constituting about 1.34 per cent, of the total cases. Colloid degeneration may affect the cells of an ordinary cancer, producing a partial metamorphosis. In true colloid cancer, however, the tissue as a whole presents, from the first, a tendency to colloid degeneration. The entire mamma is commonly affected, and it is greatly enlarged, while it presents a hard feeling like that of acute scirrhus. On section the tumour has a flickering gelatinous appearance. Under the microscope there is the usual pronounced stroma with colloid material in the meshes. In the midst of the colloid masses there are often seen groups of cells, the remains of the epithelium.

A very infrequent variety is sometimes described under the designation Mucous cancer. It forms a large gelatinous tumour which, on microscopic examination, shows epithelial masses embedded in a gelatinous flickering stroma.

Cysts are not of frequent occurrence in cancers, but in some cases cystic formation is so characteristic as to warrant the name of Cystic cancer.