Introduction
A dermoid cyst is a benign, developmental cystic lesion that commonly arises from ectodermal tissue. The cyst is lined by a stratified squamous epithelium and frequently contains derivatives of the skin such as hair follicles, sebaceous glands, and sometimes teeth. Although the term “cyst” suggests a simple fluid-filled structure, dermoid cysts are composed of a variety of tissue types and are considered a type of teratoma. They are most frequently encountered in the midline of the head and neck, the ovaries, and the ovaries’ adjacent pelvic structures. Because of their variable presentations and potential for complications, dermoid cysts are a focus of clinical and research interest in many specialties, including otolaryngology, obstetrics, gynecology, and radiology.
The presence of ectodermal elements outside the normal anatomical location indicates a developmental anomaly that arises during early embryogenesis. Dermoid cysts are typically discovered in childhood or adolescence, but they can remain asymptomatic for decades and present later in adulthood. While most dermoid cysts remain harmless, they can occasionally become infected, rupture, or, in rare cases, undergo malignant transformation. The management of dermoid cysts depends on their size, location, symptomatology, and risk of complications, and often involves surgical excision with or without adjunctive imaging and histopathologic evaluation.
History and Background
The term “dermoid” derives from the Greek words “derma” (skin) and “oid” (like), reflecting the cyst’s capacity to contain skin-like tissue. Early descriptions of dermoid cysts appear in the work of 18th‑century anatomists who observed cystic lesions containing hair or sebaceous material in the midline of the face. By the early 20th century, the classification of cystic lesions of the craniofacial region had become more refined, distinguishing dermoid cysts from epidermoid cysts and teratomas based on the presence or absence of adnexal structures.
The first systematic classification of cystic lesions based on embryologic origin was introduced in the 1940s, establishing a foundation for contemporary terminology. Over the following decades, advances in imaging technology, especially computed tomography (CT) and magnetic resonance imaging (MRI), improved the ability to preoperatively identify dermoid cysts and plan surgical approaches. More recent molecular studies have begun to elucidate the genetic factors underlying the development of these lesions, although the exact mechanisms remain incompletely understood.
Classification
By Location
- Head and Neck Dermoid Cysts – the most common type, typically arising in the midline of the lower eyelid, upper lip, nasal base, or periorbital region.
- Orbital Dermoid Cysts – often located in the superior or inferior rectus muscle, presenting with proptosis or diplopia.
- Ovarian Dermoid Cysts – also called mature cystic teratomas, occurring in the ovary and sometimes extending into the pelvic cavity.
- Other Sites – include dermoid cysts of the mandible, nasopharynx, sacrum, and other midline structures.
By Histologic Composition
- Epidermoid Cysts – lined by stratified squamous epithelium but lacking skin appendages.
- Dermoid Cysts – contain skin appendages such as hair follicles, sebaceous glands, or sweat glands.
- Mature Cystic Teratomas – contain tissues from all three germ layers (ectoderm, mesoderm, endoderm).
By Pathologic Features
- Simple Dermoid – cyst wall contains only ectodermal derivatives.
- Complex Dermoid – cyst wall includes additional mesodermal or endodermal structures such as muscle fibers, cartilage, or mucous glands.
- Malignant Transformation – rare occurrence of squamous cell carcinoma or other malignancies arising within a dermoid cyst.
Pathogenesis and Embryology
Embryonic Origins
Dermoid cysts result from sequestration of ectodermal tissue during embryogenesis. During the early stages of development, the ectoderm folds and folds, forming structures such as the neural tube and the surface ectoderm. In some cases, small pockets of ectoderm become isolated from the main epithelium and are trapped within deeper layers of tissue. These sequestrated cells retain the ability to differentiate into various ectodermal derivatives, giving rise to the diverse structures observed within dermoid cysts.
The midline of the body is particularly susceptible to this process because of the complex folding patterns that occur as the face and neck structures develop. The cranial and orbital dermoid cysts are thought to arise from ectoderm trapped during the fusion of the frontonasal, maxillary, and mandibular processes. Ovarian dermoid cysts likely result from ectodermal inclusions within the developing ovarian primordium.
Genetic and Molecular Factors
Studies of familial cases and syndromic associations have suggested that certain genetic mutations may predispose individuals to the development of dermoid cysts. Variants in genes involved in ectodermal differentiation and cell adhesion, such as PAX9 and FGFR2, have been implicated, though large-scale genome-wide association studies are still lacking. Epigenetic modifications during early development may also influence the propensity for ectodermal sequestration, but the precise mechanisms remain a focus of ongoing research.
Clinical Presentation
Head and Neck Dermoid Cysts
Patients with dermoid cysts in the head and neck region frequently present with a slowly enlarging, painless mass. Common locations include the lower eyelid, upper lip, or midline nasal base. On examination, the lesion may feel firm, mobile, and may exhibit a characteristic “cystic” texture. In some cases, the cyst may produce a discharge containing sebum or hair. Proximity to the orbit or the nasolacrimal duct can lead to visual disturbances, epiphora, or nasal obstruction.
Orbital Dermoid Cysts
Orbital dermoid cysts are often identified by proptosis or ocular motility disturbances. Because the cyst may compress extraocular muscles, patients may experience diplopia or restricted eye movement. The cyst can also exert pressure on the optic nerve, leading to visual field deficits if left untreated. Radiologic imaging typically reveals a well‑defined, low‑density lesion that may contain fat or calcifications.
Ovarian Dermoid Cysts
Ovarian dermoid cysts frequently remain asymptomatic and are discovered incidentally during imaging for unrelated reasons. When symptoms occur, they may include lower abdominal pain, pelvic fullness, or menstrual irregularities. Complications such as torsion, rupture, or infection can cause acute abdominal pain and may necessitate emergency surgical intervention.
Other Locations
Dermoid cysts arising in the sacrum or nasopharynx may present with back pain, urinary frequency, or nasal obstruction, respectively. The exact presentation depends on the cyst’s size and its relationship to surrounding structures.
Diagnosis
Clinical Evaluation
A thorough history and physical examination are the initial steps in diagnosing dermoid cysts. Clinicians assess the lesion’s size, location, consistency, and relation to adjacent anatomical landmarks. History of rapid growth, pain, or recent infection raises concern for possible complications or malignant transformation.
Imaging Techniques
Ultrasound
Ultrasound is the first-line imaging modality for superficial dermoid cysts such as those in the eyelid or upper lip. It can differentiate cystic from solid masses and identify internal echoes suggestive of hair or sebaceous material.
Computed Tomography (CT)
CT provides detailed visualization of bone involvement and calcifications. Dermoid cysts typically appear as low‑density, well‑circumscribed lesions, often containing fat‑dense areas. CT is particularly useful for preoperative planning in orbital and craniofacial lesions.
Magnetic Resonance Imaging (MRI)
MRI offers superior soft-tissue contrast and can detect cyst contents, such as fat, proteinaceous fluid, or calcifications, without radiation exposure. Typical MRI findings include hyperintense signals on T1-weighted images and variable signals on T2-weighted images, reflecting the cyst’s heterogeneous composition.
Other Modalities
Positron emission tomography (PET) scans are occasionally used when malignancy is suspected. However, PET is not routinely indicated for benign dermoid cysts.
Histopathologic Examination
Definitive diagnosis requires histopathologic evaluation of the excised cyst wall. The presence of stratified squamous epithelium, keratin debris, hair follicles, sebaceous glands, and other skin appendages confirms a dermoid cyst. In contrast, epidermoid cysts lack adnexal structures, and teratomas contain tissues from multiple germ layers. Immunohistochemical staining for cytokeratin, S100, and other markers assists in distinguishing benign from malignant lesions.
Management and Treatment
Surgical Removal
Complete surgical excision is the standard treatment for symptomatic dermoid cysts. For orbital cysts, a transcutaneous approach or a lateral orbitotomy may be employed to avoid damage to the extraocular muscles and optic nerve. In cases where the cyst is adherent to critical structures, careful dissection is required to preserve function. For ovarian dermoid cysts, laparoscopic cystectomy is the preferred minimally invasive technique, while larger or complicated cysts may necessitate laparotomy.
Non‑Surgical Approaches
In rare cases where surgery is contraindicated due to patient comorbidities or cyst location, observation with periodic imaging may be appropriate. However, the risk of complications often outweighs the benefits of watchful waiting. In some instances, steroid therapy may reduce inflammation in an infected dermoid cyst, but it does not resolve the underlying lesion.
Adjunctive Therapies
Antibiotic therapy is reserved for infected cysts, while surgical drains may be used to prevent fluid accumulation. For cysts that have ruptured into surrounding tissues, aggressive debridement and wound care are essential to prevent abscess formation.
Complications and Prognosis
Infection
Dermoid cysts can become secondarily infected, presenting with redness, warmth, pain, and purulent discharge. Infection may spread to adjacent structures, such as the orbit or the peritoneum, and may require systemic antibiotics and surgical drainage.
Recurrence
Incomplete excision is the main risk factor for recurrence. Residual cyst wall tissue can continue to grow, leading to re‑appearance of the mass. Regular follow-up imaging helps detect early recurrence and allows timely intervention.
Malignant Transformation
Although rare, malignant transformation occurs in approximately 1–2% of ovarian dermoid cysts. Squamous cell carcinoma, adenosquamous carcinoma, and, less frequently, other carcinomas have been reported. Risk factors include advanced age, large cyst size, and presence of solid components on imaging. Early surgical removal reduces the likelihood of malignant progression.
Prognosis
When appropriately managed, dermoid cysts carry a favorable prognosis. The majority of patients achieve complete resolution following surgical excision. Long‑term outcomes are influenced primarily by the cyst’s size, location, and potential for complications. Routine postoperative surveillance is recommended, particularly for ovarian dermoid cysts, to monitor for recurrence or malignant change.
Epidemiology
Dermoid cysts are relatively common congenital lesions, with an estimated incidence of 1 in 1,000 live births for ovarian dermoid cysts alone. Head and neck dermoid cysts are more prevalent in children and adolescents, with a slight male predominance in orbital locations and a female predominance in ovarian cysts. The prevalence of dermoid cysts increases with age for ovarian lesions, reflecting the cumulative risk of cyst development over time. Geographic variations in incidence have been observed, potentially reflecting genetic or environmental factors.
Research and Advances
Genetic Studies
Recent genome-wide association studies have identified loci on chromosome 6q12 and 14q13 that may be associated with dermoid cyst development. These findings suggest a polygenic contribution to ectodermal sequestration. Further research is needed to delineate the interplay between genetic predisposition and environmental triggers.
Immunohistochemical Markers
The application of immunohistochemistry has improved the accuracy of diagnosing dermoid cysts versus other cystic lesions. Markers such as cytokeratin 14, p63, and Ki‑67 provide insights into the proliferation status of the cyst epithelium, while S100 and HMB‑45 help identify melanocytic components that may be present in some dermoid cysts.
Minimally Invasive Surgery
Advancements in laparoscopic and endoscopic techniques have reduced postoperative morbidity associated with cyst removal. Enhanced imaging guidance, such as intraoperative ultrasound, allows surgeons to delineate cyst boundaries more precisely, decreasing the risk of incomplete excision.
Non‑Surgical Therapies
Investigational treatments involving targeted molecular agents have been proposed for cysts refractory to conventional surgery. Early trials of epidermal growth factor receptor inhibitors in dermoid cysts with malignant transformation have shown limited efficacy, underscoring the need for more robust therapeutic options.
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