It has been already pointed out that cysts frequently complicate other tumours, especially adeno-fibromas or sarcomas, but sometimes cancers. Cysts also occur independently, and they too most frequently originate from the gland structures.

Most cysts of the mamma belong to the group of Retention cysts, arising in consequence of obstruction of the ducts. The cause of obstruction is sometimes an interstitial inflammation, and in that case the cysts will usually be small and multiple, just as they are in the kidneys in interstitial nephritis. In other cases the cause is obscure, and as the cysts may assume a large size the origin is perhaps embryonic.

(1) Multiple cysts in old people (Involution cysts) occur in connection with involution of the gland. The cysts are usually small, about the size of small shot or hemp-seed, but may be larger. When unopened they have a greenish or blackish appearance, and they contain a glairy fluid in which fat and epithelial cells are present.

(2) Simple cysts may grow to a large size, forming tense thin-walled sacs. They are usually single, but if of small size they may be multiple. Their contents vary considerably, being usually serous or sero-sanguineous, but sometimes they are deep brown in colour, and contain fat and cholestearine. In some cases they contain milky fluid, in which case they would be called galactoceles.

(3) Galactoceles or Lacteal cysts arise usually when the gland is active. They are found chiefly in the neighbourhood of the nipple, arising by dilatation of the larger ducts. They contain milk, usually like ordinary milk, but sometimes altered so as to resemble cream or thickish oil, or curd, or butter. These cysts are usually solitary, and are very rare.

(4) Connective tissue cysts have been recently described and are supposed to be of lymphatic origin. They have thick walls and the connective tissue may be indurated around them. Hence they resemble scirrhus in their clinical aspects. The internal surface is lined with a flat endothelium. The cysts are single or multiple.

Parasites In The Mamma

The only parasite of any consequence is the Echinococcus which forms hydatid cysts. These may be with difficulty discriminated from simple cysts, and as there is sometimes considerable induration around them, they may also be mistaken for cancers.

The Cysticercus cellulosae has also been observed in the mamma (Gruermonprez).

Literature

Tumours - Astley Coopee, Illustr. of dis. of breast, 1829; Biekett, Dis. of breast, in Holmes' Surg., iv., 1870; Veleeau, Treatise on dis. of breast (Syd. Soc. transl.), 1856; Billeoth, Die Krankh. der weibl. Brustdrusen, 1880; Creighton, Phys. and path, of breast, 2nd ed., 1886; Gross, Treat, on Tumours of mammary gland, 1880, and article in Mann's Syst. of Gynecology, 1888; Beyant, Diseases of breast, 1887; Bogee Williams, Dis. of breast, 1894. Eczema of nipple - Paget, St. Barth. Hosp. Bep., 1874; Butlin, Med. chir. trans., lx. and lxiv.; Thin, Path, trans., xxxii., 1881, p. 218; Muneo, Glasg. Med. Jour., xvi., 1881; Daeiee, Ann.;de Dermat., x., 1889; Wickham, Arch, de path, exper., ii., 1890; Boeck, Arch. f. Dermat., xxiii., 1891; Peteesen, Centralb. f. Bakt., xiv., 1893; Hutchinson, Je., Path, trans., xli., 1890, p. 214. Cysts - Gross and Beyant, 1. c. Parasites - Haussmann, Parasiten der Brustdriise, 1874; Guermonprez, Lyon med., 1883; Thomas, Hydatid disease, 1894, vol. ii.