Pseudocystic changes occur in other tumors and in other parts of the body as the result of mucoid and colloid liquefactions. In the midst even of apparently dense and entirely defined tumor masses changes of this kind occur, and lead to formation of cavities containing fluid of variable consistence, causing the tumor when divided to present the appearance of the geodes or quartz rocks, containing cavities lined with quartz crystals. The occurrence of such cystic changes is indicated, in naming such a tumor, by prefixing the term cysto-, as cystosarcoma, cystofibroma, etc.
2. Dermoids.
Dermoids are cysts or tumors containing tissues and appendages which are developed from the epiblast, and which occur when skin and mucous membrane are not normally found. The simplest form of dermoid is a cyst whose interior is lined with modified skin, containing sebaceous glands and hair follicles, from which often numerous long hairs are produced. Even sweat glands may be present. Its cavity is occupied by mixed material, pultaceous in character, made up of sebum, cholesterine, and growing hairs which are often rolled into balls. The sebum is the product of the glands contained in the cyst wall.
A complex form of so-called dermoid cyst is met with in which there are unstriped muscle fiber, teeth, mammary glands, etc. These belong rather to the class of teratomas, as they contain more or less tissue not of epiblastic origin.
A dermoid tumor is one lacking cystic characteristics, made up of tissue largely developed from the epiblast, with more or less tissue of mesoblastic origin. Such a tumor may contain much connective tissue, fat, fetal hyaline cartilage, and nerve tissue, while from its exterior long hair may grow, and teeth project from its surface or be embedded within its substance. Such tumors are generally found in the pharynx and about the rectum.
The explanation of dermoids and teratomas may be gleaned from embryology, and rests upon the arrangement of the different blastodermic layers of the developing ovum, and upon the facts already alluded to in explaining Cohnheim’s hypothesis of the origin of tumors. Strictly speaking, a dermoid should contain only that which may be developed from the epiblastic layer. It is well known that teeth and hair, as well as sebaceous material, are epiblastic products. Consequently such material may be found within a dermoid and needs no further explanation than an epiblastic inclusion, according to Cohnheim’s views. But so soon as such a tumor contains bone, muscle, etc. (i. e., tissues of mesoblastic origin), we should drop the term dermoid and consider it a teratoma. Such is the distinction between these two terms. According to Wilm’s researches, any tumor of this sort which contains epithelial products as teeth or hair is sure to contain also mesoblastic elements, and thus to belong to the latter. The term epidermoids has been applied to the former.
The most prominent characteristics of dermoid cysts are: (1) Skin, which may be thick or thin, lined with papillæ, containing more or less pigment, its deeper layers possessing a quantity of fat. (2) Hair, which next to skin is the most constant structure found in dermoids; this may be present in trifling amount or in long coils or balls. It is of interest that in dermoids found in animals covered with wool we find the same character of hairy structure, while in birds dermoids contain feathers rather than hairs. (3) Sebaceous glands and their peculiar secretion are invariably found. These may be of large size, and sebaceous retention cysts may be seen in the walls of dermoids. Sometimes horny matter or tissue is found in these, indicating the same relation between horn and sebaceous structures, as we see upon the external skin in other instances. So, too, material resembling the texture of finger-nails is occasionally found projecting into the cavity.
The fluid or semifluid contents of these cysts consist usually of sebaceous material, cholesterin, epithelial debris, etc. Sometimes it is thick, sometimes thin—and occasionally consists almost entirely of mucus.
It is not uncommon to find structures in ovarian dermoids closely analogous to, or actually resembling, mammary glands. These may be mere nipple-like processes of skin, or completely developed mammæ, well formed, but without ducts or gland tissue, may occupy such a cyst. These really are pseudomammæ, because they have no ducts. Nevertheless, glandular tissue is not always absent. This resemblance proceeds even farther, in that in some of these ovarian mammæ changes occur analogous to those which take place in normal breasts.
The epiblast seems to have the power of developing mammary glands or supernumerary mammæ in many locations—in fact, upon any part of the body surface. About the thorax they are common; upon the abdomen they are rarely observed; and they have been found even upon the labia.