Dermoid cyst overview

# Overview
The term "dermoid cyst" was first coined by Leblanc, in 1831 following the removal of a lesion that resembled skin at the base of a horse's skull. Dermoid cysts were first clearly described in 1885 by Bytlin. In 1891, Chairi was the first to propose that the tumors in the floor of the mouth originated from the entrapped epidermoid cells during the embryonic age. Dermoid cysts may be classified according to the mode of occurrence into congenital and aquired types and into several subtypes based on the anatomical location. Dermoid cyst arises from the entrapped embryonal ectodermal cells during the fetal development and are generally formed of skin, hair follicles, hair follicles, teeth and sebaceous glands. Acquired dermoid cysts may result from iatrogenic or traumatic implantation of the epithelial cells that subsequently grow. On gross pathology, uniloculated cysts lined by skin, containing sebaceous glands, hair follicles, and teeth are characteristic findings of dermoid cysts. On microscopic histopathological analysis, fibro collagenous cysts lined by stratified squamous epithelium, with epidermal appendages such as hair follicles, sweat and sebaceous glands are characteristic findings of dermoid cysts. Dermoid cyst must be differentiated from teratoma, as well as other common benign tumors that develop in the head and neck, ovaries, or spine (such as pilar cysts, steatocystoma, pilomatrixoma, encephalocele, vascular malformations, lipoleiomyoma, pilonidal cyst, and lipoma). Dermoid cysts are rare benign tumors. Spinal dermoid cysts commonly affect  individuals in their second or third decades of life. Males are more commonly affected with spinal dermoid cysts than females. Dermoid cysts in other locations affect men and women equally. There is no racial predilection to the dermoid cysts. The majority of patients with dermoid cysts are asymptomatic. If left untreated, dermoid cysts gradually increase in size and produce symptoms depending upon their anatomical location. Depending on the anatomical location of the tumor, the prognosis may vary. The majority of patients with ovarian dermoid cysts are asymptomatic. They are discovered incidentally on routine physical exam or imaging for other reasons. Physical examination findings in patients with dermoid cyst may include a painless swelling that may be freely mobile or fixed to the skin and deeper structures. Congenital dermoid cysts localized to the scalp, neck or trunk are usually visible at birth. Xray, CT, MRI, and ultrasound are helpful in the diagnosis of dermoid cysts. Surgery is the mainstay of treatment for dermoid cysts.

# Historical Perspective
The term "dermoid cyst" was first coined by Leblanc, in 1831 following the removal of a lesion that resembled skin at the base of a horse's skull. Dermoid cysts were first clearly described in 1885 by Bytlin. In 1891, Chairi was the first to propose that the tumors in the floor of the mouth originated from the entrapped epidermoid cells during the embryonic age.

# Classification
Dermoid cysts may be classified according to the mode of occurrence into congenital and aquired types and into several subtypes based on the anatomical location.

# Pathophysiology
Dermoid cyst arises from the entrapped embryonal ectodermal cells during the fetal development and are generally formed of skin, hair follicles, hair follicles, teeth and sebaceous glands. Acquired dermoid cysts may result from iatrogenic or traumatic implantation of the epithelial cells that subsequently grow. On gross pathology, uniloculated cysts lined by skin, containing sebaceous glands, hair follicles, and teeth are characteristic findings of dermoid cysts. On microscopic histopathological analysis, fibro collagenous cysts lined by stratified squamous epithelium, with epidermal appendages such as hair follicles, sweat and sebaceous glands are characteristic findings of dermoid cysts.

# Causes
Dermoid cysts are caused by the entrapped embryonic ectodermal cells in the embryonic lines of fusion during the fetal development. Acquired dermoid cysts may be caused by iatrogenic or traumatic implantation of the epithelial cells that subsequently grow.

# Differentiating Dermoid Cyst from other Diseases
Dermoid cyst must be differentiated from teratoma, as well as other common benign tumors that develop in the head and neck, ovaries, or spine (such as pilar cysts, steatocystoma, pilomatrixoma, encephalocele, vascular malformations, lipoleiomyoma, pilonidal cyst, and lipoma).

# Epidemiology and Demographics
Dermoid cysts are rare benign tumors. Spinal dermoid cysts commonly affect  individuals in their second or third decades of life. Males are more commonly affected with spinal dermoid cysts than females. Dermoid cysts in other locations affect men and women equally. There is no racial predilection to the dermoid cysts.

# Risk Factors
There are no established risk factors for dermoid cysts.

# Screening
There is insufficient evidence to recommend routine screening for dermoid cysts.

# Natural History, Complications and Prognosis
The majority of patients with dermoid cysts are asymptomatic. If left untreated, dermoid cysts gradually increase in size and produce symptoms depending upon their anatomical location. Common complications of ovarian dermoid cysts include torsion, rupture, and infection. Common complications of periorbital dermoid cysts include inflammation and recurrence when not completely excised. Rupture is the most common complication of spinal dermoid cysts. Common complications of intracranial dermoid cysts include compression of adjacent structures from the mass effect and rupture of the cysts. Infection is the most common complication of dermoid cysts of the floor of the mouth. Malignant transformation usually into squamous cell carcinoma is a rare complication of dermoid cysts. Depending on the anatomical location of the tumor, the prognosis may vary.

# Diagnosis

## History and Symptoms
Congenital dermoid cysts localized to the scalp, neck or trunk are usually visible at birth and gradually grow in size. The majority of patients with ovarian dermoid cysts are asymptomatic. They are discovered incidentally on routine physical exam or imaging for other reasons. Large ovarian dermoid cysts may present with abdominal pain or abdominal mass. Symptoms of spinal dermoid cyst may include motor disturbances (hemiplegia), sensory disturbances, bowel and/or bladder dysfunction, fecal retention or incontinence, and urinary retention or incontinence. Headache is the most prominent symptom of intracranial dermoid cyst. Symptoms of dermoid cysts of the floor of the mouth may include dysphagia, dysarthria, dyspnea (when the lesions are quiet large), and speech delay.

## Physical Examination
Physical examination findings in patients with dermoid cyst may include a painless swelling that may be freely mobile or fixed to the skin and deeper structures. Congenital dermoid cysts localized to the scalp, neck or trunk are usually visible at birth. A tuft of hairs emanating from a midline nasal depression or nodule may represent a nasal dermoid cyst. A tarsal dermoid cyst may present as a firm, non tender nodule in the eyelid. Periorbital demoid cysts usually appear on the lateral aspect of the eyebrow. Dermoid cysts of the scalp or orbit may cause pressure erosion of the underlying bone which appears as a punched out defect in the skull x rays. A double-chin appearance is a common finding if the cyst develops below the mylohyoid muscle.

## Laboratory Findings
There are no diagnostic laboratory findings associated with dermoid cysts.

## X Ray
X rays may be helpful in the diagnosis of dermoid cysts. Findings on pelvic x ray suggestive of ovarian demoid cyst may include calcifications and tooth components. On x-rays, dermoid cysts are characterized by a focal lucency due to the fatty sebum. X rays may appear normal in other dermoid cysts.

## CT
CT scan may be helpful in the diagnosis of dermoid cyst. Findings on CT scan suggestive of ovarian dermoid cyst include low attenuating areas of fat and fat-fluid levels, rokitansky protuberance, soft tissue plugs, and cauliflower appearance with irregular borders. Findings on CT scan suggestive of spinal dermoid cysts include well defined mass isodense to cerebrospinal fluid, often with hypodense components (fat) and calcification, widening of the spinal canal, flattening of the pedicles and laminae, and osseous erosions. Findings on CT scan suggestive of intracranial dermoid cyst include well defined low attenuating (fat density) lobulated mass with calcifications in the wall.

## MRI
MRI is helpful in the diagnosis of dermoid cyst. Findings on MRI suggestive of dermoid cyst include hypointense (due to the water content) or hyperintense (due to the presence of fatty secretions of sebaceous glands) T1 signal, hyperintense T2 signal, and no enhancement or mild rim enhancement on contrast T1 signal.

## Ultrasound
Ultrasound may be helpful in the diagnosis of ovarian dermoid cyst. Findings on pelvic ultrasound suggestive of ovarian dermoid include unilocular, cystic adnexal mass with mural components, diffusely or partially echogenic mass with posterior sound attenuation (from the sebaceous material and hair within the cyst cavity), an echogenic interface at the edge of mass that obscures deep structures, mural hyperechoic dermoid plug, presence of fluid-fluid levels, and multiple thin, echogenic bands caused by hair in the cyst cavity (the dot-dash pattern).

## Other Imaging Findings
Scintigraphy may be performed to differentiate a submental dermoid cyst from an ectopic thyroid tissue swelling.

## Other Diagnostic Studies
There are no other diagnostic findings associated with dermoid cysts.

# Treatment

## Medical Therapy
The mainstay of therapy for dermoid cysts is surgery.

## Surgery
Surgery is the mainstay of treatment for dermoid cysts.