mercoledì 18 giugno 2008
Oral cavity dermoid
Axial contrast enhanced CT (Figure 1 and Figure 2) demonstrate a well circumscribed cystic mass (Figure 1) in the root of tongue. The lesion is heterogeneous with focal oval areas of fat attenuation within the lesion. There is a thin wall with no significant surrounding inflammatory changes (Figure 3). The lesion is in the midline between the genioglossus muscles (Figure 4).
Diagnosis: Oral cavity dermoid and epidermoid
Epidermoid and dermoid cysts are benign lesions encountered throughout the body, with 7% occurring in the head and neck area. The orbit is the most common site in the head and neck for these congenital lesions. They rarely occur within the oral cavity, representing less than 0.01% of all oral cavity cysts.
These congenital cysts are dysembryogenetic lesions that arise from ectodermal elements entrapped during the midline fusion of the first and second branchial arches between the third and fourth weeks of intrauterine life. Acquired cysts may be derived from traumatic or iatrogenic inclusion of epithelial cells or from the occlusion of a sebaceous gland duct.
The cysts can be classified as epidermoid when the lining presents only epithelium, dermoid cysts when dermal appendages are found, and teratoid cysts when other tissue such as muscle, cartilage, and bone are present. The teratoid type is the only variety that may have a malignant change.
Anatomically, these oral cavity cystic lesions most commonly involve the floor of mouth and may occur in the root of tongue (ROT), submandibular space (SMS) or sublingual space (SLS). Dermoid cysts generally present with slow and progressive growth, and even if they are congenital, the diagnosis is usually possible in the second or third decade of life. Midline cysts of the floor of the mouth present as painless subcutaneous or submucosal lesions. When large, they can displace the tongue and result in dysphagia, dysphonia or dyspnea.
Epidermoids present on imaging as low density, unilocular, well circumscribed simple cystic lesion. Dermoid cysts are usually more heterogeneous with fatty internal material and possibly calcification.
The treatment of dermoid cysts of the floor of the mouth is extracapsular excision with an intraoral or external approach, depending on the size of the lesion and the position relative to the mylohyoid muscle. The entire cyst must be removed to prevent recurrence.