Dermoid

DERMOID, dermoid cyst, a single- or multi-chambered cyst-like tumorous formation having a wall constructed similarly to skin. The wall of a dermoid consists of a connective tissue base corresponding to the cutis with a papillary layer, in which all skin appendages are located—sebaceous glands, hair follicles, and hair; the inner surface of the dermoid wall is covered with epidermis with its various layers: rete Malpighii, stratum granulosum, and stratum corneum. The contents of the cysts consist of a pasty, viscous, tallow-like, or oily mass, which contains hair, for the most part growing chaotically on the inner surface of the cavity and matted into clumps (see separate table, fig. 3); upon microscopic examination of this mass, one can detect an abundant content of epidermal scales, fatty detritus, and cholesterol. A dermoid develops predominantly in those places where, in the embryonic period, folds of the epidermis going deep into the tissue are formed or where furrows and fissures close, since it is precisely in such places that favorable conditions are created for the detachment of individual parts of the ectoderm, from which dermoids develop. Such "fissural" dermoids are most often encountered on the face, the occipital region, the neck, on the floor of the oral cavity, in the eye socket, in the anterior mediastinum, and in the pelvic cellular tissue. If dermoids are devoid of skin appendages and their wall is constructed only of epidermis, and the contents consist of cells of the latter that have separated by desquamation, then these tumors are called epidermoids. Formations similar to dermoids can arise on the basis of traumatic implantation of particles of the epithelial covering into the subcutaneous cellular tissue, which is usually observed in the region of the hands. Among ovarian teratomas, cyst-like formations are sometimes observed which have the structure of a dermoid, and here they are more often called dermoid cysts. Upon removal of the tallow-like contents and hair, on the inner surface of a dermoid cyst, one usually finds a swelling protruding in the form of a tubercle (dermoid tubercle), in which, upon sectioning, diverse tissues are discovered, in most cases derivatives of all three germ layers: bone plates, on which well-developed teeth are often located, cartilage, glandular ducts and tubes, and often nervous tissue, etc. This tubercle is covered with a skin covering with its derivatives, whereas in the rest of the cavity the inner surface may be lined with cylindrical or cuboidal epithelium. (Regarding the origin of the ovarian dermoid cyst, see Teratoma.) Treatment is surgical: enucleation of the dermoid cyst, which is often difficult due to tight adhesions with surrounding tissues.