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Author: Vanessa Ngan, Staff Writer, 2003.
A dermoid cyst is a choristoma, a benign tumour consisting of microscopically normal tissue derived from germ cell layers foreign to that body site. In the skin, dermoid cysts are made up of epidermal and dermal components: keratinocytes, hair follicles and hair, and sweat glands.
Dermoid cyst (in an unusual location)
Dermoid cyst of the skin appears in early childhood, with about 40% present at birth and most appearing by the age of 5 years. The cyst develops during skin tissue development in the embryonic stage. They occur on fusion lines.
Dermoid cysts in other parts of the body, such as within the skull, spine or abdominal cavity particularly the ovaries, may present at any time in people of all ages.
Dermoid cysts occur mostly on the face (outer eyebrow, eyelid, upper nose), neck, or scalp but they may occur anywhere in the body. The cyst is usually a solitary, firm, dough-like lump and ranges in size from 0.5–6 cm in diameter. It can be associated with a nearby pit and/or sinus tract to underlying tissues.
A dermoid cyst is usually removed surgically by excision biopsy. Prior to surgery, it may be investigated with ultrasound scan to determine the extent of underlying tissue involvement. If there is a nearby sinus tract, this is often explored using a sinogram.
Dermoid cysts in other parts of the body such as intracranial cysts, intraspinal cysts, intra-abdominal cysts and cystic tumours of the ovary may be difficult to treat and require special surgical techniques to remove the lesion and prevent possible complications.
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