Dermoid cysts of the oral cavity are rare. When they do occur, the most common site is the floor of the mouth. Intralingual dermoid cysts are even more rare, and until now, there were only 15 such reports in the English-language literature. In this article, we describe two additional cases. Magnetic resonance imaging is extremely helpful in establishing a differential diagnosis. Surgical excision is recommended to correct deglutition and speech problems. Its rarity notwithstanding, dermoid cyst should be considered in the differential diagnosis of tongue masses in the younger population.
Dermoid cysts of the oral cavity rarely occur in the tongue. To date, only 15 such cases have been reported. In this article, we report two additional cases of intralingual dermoid cyst, and we discuss the management of this lesion.
Case 1. A 5-month-old boy was admitted with a 1-week history of irritability, poor feeding, and fever. He had previously been treated with oral antibiotics and eardrops. The patient was the product of a full-term pregnancy and a normal, spontaneous vaginal delivery. He had no other significant medical history.
On admission, the patient's temperature was 100.9[degrees] F. The physical examination was remarkable for an enlarged tongue, with induration of the ventral surface. The floor of the mouth was not elevated or firm. Pertinent laboratory values included a white blood cell count of 23.5 x [10.sup.9]/L (58.8% neutrophils, 34.1% lymphocytes, and 3.1% mono-cytes). Blood culture, urinalysis, and cerebrospinal fluid testing disclosed no evidence of bacterial invasion. Magnetic resonance imaging (MRI) revealed the presence of a large mass in the midportion of the tongue, with an area of central necrosis and a suggestion of an inferior extension into the floor of the mouth (figure 1).
The mass was excised through a horizontal incision on the ventral surface of the tongue, after which a blunt dissection was used to expose the encapsulated midline cystic lesion, which proved to have a posterior tract. The mass was removed in its entirety. A Gram's stain of the purulent material in the cyst revealed numerous gram-sensitive cocci and a few gram-negative rods. Final cultures grew streptococcus. A yeast organism was cultured. The final pathology revealed that the lesion was a dermoid cyst of the dermoid type. The patient recovered without complication and was discharged 4 days postoperatively. He has remained well at 2-year followup.
Case 2. A 17-year-old girl with a history of von Willebrand' s disease and pseudocholinesterase deficiency was referred to our department with a 1-year history of a progressively enlarging tongue mass. She denied experiencing any respiratory distress, pain, discharge from the mass, or fever.
The physical examination was unremarkable except for a slightly tender tongue and the mass protruding from the dorsal surface. MRI demonstrated a 4 x 3.1 x 1.9-cm cystic mass in the midportion of the tongue inferiorly, with no extension into the posterior aspect (figure 2). Fine-needle aspiration yielded 25 ml of slightly milky fluid, which suggested a diagnosis of dermoid cyst.
The patient underwent surgery via the transoral route under general anesthesia delivered by nasotracheal intubation. A vertical incision was made along the ventral midline raphe of the tongue. An encapsulated mass measuring 5 x 6 cm was dissected from the tongue base and intrinsic tongue musculature. Because of the history of von Willebrand' s disease, a Hemovac drain was placed. The patient remained intubated for 24 hours postoperatively because of tongue swelling. She was successfully extubated on postoperative day 1, and the Hemovac drain was removed on day 2. She was tolerating a regular diet by the time of her discharge on day 5.
Histopathologic examination revealed that the cyst was lined with keratinized squamous epithelium, which contained skin adnexal sebaceous glands and hair follicles, both of which are consistent with a dermoid cyst (figure 3). Her speech and deglutition were normal after surgery. She has done well 2 years following surgery.
The tongue comprises two parts that have different embryologic origins; the anterior two-thirds of the tongue arise from the ectoderm and the posterior one-third from the endoderm. Formation of the tongue begins in the human embryo during week 4 of gestation. The anterior two-thirds originates from the paired lateral lingual swellings that are contributed by the first branchial arch. These swellings subsequently fuse at the midline and join with the tuberculum impar. The remaining posterior one-third of the tongue arises from a second swelling (the hypobranchial eminence or copula), which is made up of mesoderm of the second, the third, and a portion of the fourth pharyngeal arches. The sulcus terminalis, which extends along the line of circumvallate papillae, demarcates the junction of the anterior and posterior portions of the tongue. At 7 weeks of gestation, the intrinsic musculature of the tongue is formed by the first four occipital somites, which are innervated by the hypoglossal nerve. 
Congenital dermoid cysts are believed to arise from epithelial debris or rests that become trapped during the midline fusion of the branchial arches.  Some of these trapped cells are totipotential blastomeres that can develop into any of the three germ layers. Acquired dermoid cysts arise from epithelium implanted during trauma, and they often occur at sites away from the midline. 
According to Meyer, dermoid cysts are histopathologically classified as epidermoid, dermoid, or teratoid.  The epidermoid type is lined with simple squamous epithelium and surrounding connective tissue. The dermoid type (which was the type seen in our two patients) is an epithelium-lined cyst that contains skin appendages. The teratoid type is also epithelium-lined, and it contains mesodermal or endodermal elements such as muscle, bones, teeth, and mucous membranes. [2,4] Of the 15 earlier-reported cases, seven were epidermoid cysts, four were dermoid cysts, and four were teratomas. 
The differential diagnosis of a lingual mass includes dermoid cyst, lingual thyroid, cystic hygroma, ranula, abscess, and congenital retention cyst of the sublingual gland. Of all dermoids, 6.9% occur in the head and neck area, and 23% of these are located in the floor of the mouth.  They are very rarely located in the tongue. Dermoid cysts in the floor of the mouth can appear in two different ways, depending on their relationship to the mylohyoid muscle; cysts superior to this muscle are seen as intraoral swelling, while those inferior to it manifest as swelling in the midline of the neck.
Patients with an intralingual dermoid cyst have different types of signs and symptoms, including asymptomatic tongue enlargement, feeding difficulties (infants), and recurrent infection, with or without sinus fistulae. When cysts become large enough, patients can become unable to close the mouth or chew and speak normally.
MRI and computed tomography (CT) can delineate the internal architecture and reveal the relationship of the cyst to the mylohyoid muscle. Dermoid cysts typically appear as well-circumscribed unilocular masses that are either purely cystic or heterogenous because of the presence of cholesterol, desquamated epithelial debris, and skin appendages. CT will typically show a midline unilocular mass with a well-defined capsule that can be enhanced with contrast material. MRI characteristics are more variable, and dermoid cysts are usually iso- or hypointense to muscle on T1-weighted images and hyperintense or heterogenous on T2-weighted images, depending on their internal content.
Treatment is complete surgical removal, usually through an incision in the ventral surface of the tongue. While making this incision, the surgeon should take care to avoid both Wharton's ducts. No recurrence has been reported. Marsupialization has been performed with success in cases when excision of the entire cyst was not feasible. 
From the Department of Otolaryngology and Communicative Disorders (Dr. Myssiorek and Dr. Lee), the Department of Pathology (Dr. Wasserman), and the Department of Radiology (Dr. Lustrin), The Long Island Jewish Medical Center, Albert Einstein College of Medicine, New Hyde Park, NY.
Reprint requests: David Myssiorek, MD, Long Island Jewish Medical Center, 270-05 76th Ave., New Hyde Park, NY 11040. Phone: (718) 470-7552; fax (715) 347-2320; e-mail: firstname.lastname@example.org
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