A dermoid cyst of skin is a cyst which lies deep to the skin and is lined by epithelium similar to that of skin (epidermis). So a dermoid cyst can be called an epidermal cyst. It contains thin-walled tumors that contain different amounts of fatty tissue. Occasionally, they contain horny masses and hair.
These cysts are lined by squamous epithelium and these contain pultaceous or toothpaste-like material which contains desquamated epithelial cells.
There are four types of dermoid cysts
- Sequestration dermoid
- Implantation dermoid-Acquired variety
- Teratomatous dermoid.
This is a congenital variety of dermoid cyst, which is formed by the inclusion of epithelium buried at the line of embryonic fusions. So these are found along the lines of fusion of the two embryonic segments.
This cyst is lined by stratified squamous epithelium with hair, hair follicles, sebaceous glands, and sweat glands. It contains white pultaceous, tooth paste like desquamated material with or without hair. It is the mixture of sebum, sweat, and desquamated epithelial cells.
Common sites are
- At the midline of the body particularly in the neck.
- External angular-just above the outer canthus of the eye-at the line of fusion of the frontonasal and maxillary processes.
- Post-auricular-behind the ear at the site of fusion of the mesodermal hillocks.
- On the skull at the site of fusion of the skull bones.
- At the midline of the face particularly at the root of the nose.
At the line of embryonic fusion, a few ectodermal cells are sequestrated into the deeper layer. Ultimately these cells proliferate and liquefy to form a sequestration dermoid cyst. Such cyst lies almost near the mesoderm from where the bones develop, that is why indentation is often found in the underlying bone. Sometimes the cyst starts in the mesoderm so that there may be prolongation of the cyst through the bone and a portion of the cyst may remain intracranial.
The cyst may be noticed at birth, but it is usually seen a few years later-the time taken to form the cyst.
A painless swelling, which is slowly growing is the main symptom. Cosmetic disfigurement is the main complaint. Such cyst hardly becomes big enough to cause any serious mechanical disability and rarely may become infected.
Such cysts hardly attain a size bigger than 2 cm in diameter. They are usually ovoid or spherical in shape and have a smooth surface and do not have punctum which is often found in sebaceous cysts.
The cyst feels soft and indents with pressure as the content is thick pultaceous material, a mixture of sebum, sweat, and desquamated epithelial cells.
The skin can be lifted off the cyst easily. This cyst is also free from underlying structures. There may be bony indentation when the bone lies exactly deep to the cyst.
This may show a depression in the bone underlying the cyst or a gap. Such a gap may be present when there is an intracranial extension or a fibrous band may pass through this bony gap and connect the cyst with the underlying durameter.
Complete excision of the cyst is the treatment of choice. This should be done under general anesthesia as the cyst has to be dissected from the sensitive pericranium; moreover, there may be an intracranial extension.
If preliminary X-ray shows a gap in the underlying bone, the operation has to be delayed to give an opportunity for spontaneous closure.
If there is an intracranial extension, osteoplastic flap should be removed for excision of the intracranial part.
It is an acquired dermoid and arises from indriven epithelium beneath the skin due to a puncture injury e.g. needle prick or thorn prick.
Common sites are
- Palm of the hand
It is quite common in gardeners, tailors, and women.
The cyst is usually lined by stratified squamous epithelium with no hair follicle, sweat, and sebaceous glands. The content is white cheesy material formed by desquamated epithelial cells and sebum. Hair is usually absent.
A history of puncture injury is usually available. In some cases, the patient might forget about the injury.
Swelling in the finger or the palm is usually the presenting feature. The cyst may be slightly painful.
A tense cystic swelling is found in the finger or the palm. The consistency is often firm or even hard. There may be a scar on the skin overlying the cyst. Fluctuation is very difficult to elicit as the cyst is small and tense.
The most important clinical feature is the presence of a tense cyst in the finger or the palm with a previous history of a puncture wound.
Treatment is complete excision of the cyst.
This is also an epidermal cyst, but such cyst develops from an unobliterated portion of a congenital ectodermal duct or tube.
The cyst is formed by the accumulation of secretions of the lining ectodermal cells of the unobliterated portion of an embryonic duct.
- Thyroglossal cyst: develops from the thyroglossal duct. It is the commonest example of tubulo-dermoid cyst.
- Post-anal dermoid: develops from the remnant of neurenteric canal or post-anal gut. But it is now regarded as a simple form of teratoma.
- Ependymal cyst is in the brain: formed from the sequestration of cells derived from the infolding neuroectoderm.
It is a cystic swelling which develops from the totipotent cells with ectodermal predominance. Such cyst also contains mesodermal elements like bone, cartilage, etc. Hair is almost always present in such cyst. So the usual contents are bone, cartilage, tooth, hair and cheesy material. Although the majority of these cysts are benign, a small percentage can be malignant (cancerous).
Common sites are
- Ovary-ovarian cyst
- Testis- teratoma
- Mediastinum- mediastinal cyst
- Retroperitoneum- retroperitoneal cyst
- Post- anal dermoid
Complications of Dermoid Cysts
- Pressure symptoms to the surrounding structures