The two last-mentioned names imply that the glandular structures take an important part in giving character to sarcomas of the mamma, although the connective-tissue structures are those essentially engaged.

The line of demarcation between the sarcoma and the fibroma is not absolutely distinct, and there seems no doubt that the latter may develop into the former by an atypical process of growth supervening.

The spindle-celled sarcoma is the commonest form. The cells are usually small, and there may be a considerable amount of fibrous intercellular substance. The tumour is usually hard and variously modified by the presence of 'gland tissue. The round-celled sarcoma is unusual and generally forms a soft tumour. The cells may be small so as to be like lymphoid cells, or larger. The giant-celled sarcoma is very rare; there are smaller cells and gigantic ones. The pigmented sarcoma is also rare; the cells are usually round, but sometimes spindle-shaped.

The sarcoma is generally solitary. It may be distinctly demarcated, occupying a small part of the breast, but it not infrequently extends so as to involve the whole mamma. It may grow slowly, but is apt, after a period of slow growth, suddenly to enlarge rapidly.

The Adeno-sarcoma is a tumour in which the glandular structures are specially abundant. It is usually a small comparatively isolated tumour, somewhat resembling the adeno-fibroma, and, like this tumour, it is not infrequently multiple. Under the microscope it usually shows abundant glandular structures somewhat contorted, with a spindle-celled tissue between.

The Cysto-sarcoma shows many gradations. There may be such simple dilatations as those indicated in Fig. 469, or there may be large cavities. Great complication is sometimes produced by intracystic growth of the sarcomatous tissue, as in the cystic-fibroma.

Semidiagrammatic view of dilated granular spaces in a cysto sarcoma of the mamma.

Fig. 469. - Semidiagrammatic view of dilated granular spaces in a cysto-sarcoma of the mamma. The spaces are lined with cylindrical epithelium. The tendency to intra-cystic growth is shown, especially in the upper one. These were drawn under the camera lucida so that the outlines are correct, x 62.

Besides these variations due to the mixture with glandular tissue, the sarcoma is subject to other modifications. It may contain Cartilage, as in the case from which Fig. 470 was taken. In this case the tumour contained well-formed fibrous tissue and cartilage, but also, apparently as a more recent development, spindle-celled tissue, and a tissue consisting of closely aggregated cartilage cells with little hyaline matrix. Bone also occurs occasionally.

Mucous transformation sometimes occurs, and cysts may arise in this way. There is also fatty degeneration, calcareous infiltration, and haemorrhage, especially in the quickly growing and softer forms.

Sarcomas are very ma lignant. On removal they are even more apt to return than cancers, and they also tend by metastasis to give rise to secondary tumours in internal organs, the metastasis occurring by the blood.