 Diagnosis and treatment of swellings of the floor of the mouth present many interesting problems. Among the lesions responsible for enlargements of this area is the epidermoid or epithelial inclusion cysts. These cysts are congenital in origin and are caused by an enclavement of the ectoderm at the time of closure of an embryonic fissure. For the most part they contain sebaceous glands and sebaceous secretions. However on rare occasion they may contain hair and hair follicles. While they are present at birth they usually do not become evident until later years with their growth occasionally being accelerated during puberty. When seen in the facial regions they occur most frequently in the floor of the mouth or the submetal area. These lesions are sometimes erroneously referred to as dermoid cysts. This problem was encountered on an 18 year old girl who was referred for diagnosis and treatment of a three and a half by a three and a half centimeter mass in the floor of the mouth. History reveals it was first noted approximately four years ago when a small painless asymptomatic nodule developed in the midline of the floor of the mouth. It gradually increased in size over the next three years until approximately one year ago it stabilized at its present size. There was no pain or discomfort associated with this lesion. However as it enlarged the patient noted increasing difficulty in mastication and speech. Since it was painless it did not cause alarm. It was discovered during a routine dental examination one week previous to the present time. Examination reveals no limitation of movement of the jaws. A large mass is noted protruding in the floor of the mouth between the tongue and the mandibular anterior teeth. The mass is accentuated as the patient raises her tongue and limitation of movement of the tongue is evident. Pressure in the submetal region causes the mass to become more prominent in the floor of the mouth. When the mucosa is tensed over the underlying mass a definite yellowish color is evident. Palpation reveals the mass to have a firm rubbery consistency. While the mass is slightly compressible firm resistance is encountered and the impression is readily established that the lesion feels somewhat like a rubber ball. As the mucosa is moved it is quite evident that it moves freely and independently of the underlying mass given the impression that a distinct capsule surrounds the submerged lesion. The distended vessels in the wall of the encapsulated mass are quite evident as movement of the thin over lined mucosa is continued. When confronted with a soft tissue enlargement in the floor of the mouth at least five entities must be considered. The first is infection. In this case infection can probably be ruled out because of the history, the lack of symptoms and the characteristics of the lesion. A ranula should be the second consideration since it is the most frequent lesion responsible for enlargements in this area. A representative ranula is shown in this slide. It is usually bluish white in color and is filled with a thin fluid that allows easy compression of the mass. The mucosa over lined the ranula cannot be moved independently of the underlying cyst wall. Since the lesion in our patient is yellowish white instead of bluish white in color is a firm consistency and is not soft and compressible and since the mucosa can be moved independently of the underlying mass a ranula can probably be ruled out. The next most frequently encountered enlargement of the floor of the mouth is the epidermoid inclusion cyst. The location of the lesion in this patient, the history of slow enlargement, its color and consistency and the fact that it appears to be encapsulated certainly points to this entity as the most likely diagnosis. The next lesion that must be considered is a mesodermal tumor. Any of the connective tissue structures found in this area are capable of neoplastic proliferation and while such tumors are rare they must be considered. A mesodermal tumor, a lipoma, is illustrated in these slides. These tumors may reach considerable size are firm and resistant and usually are encapsulated which allows free movement of the over lined mucosa. If the connective tissue mass happens to be a lipoma it could have a yellowish color as shown in this slide. The over lined mucosa has been excised exposing an encapsulated mass which proved to be a lipoma. Hence a mesodermal tumor must be given serious consideration in the present case. Finally, since the floor of the mouth contains salivary glands a tumor of salivary gland origin must be considered. To obtain additional information aspiration to determine the contents of the mass would be helpful. To carry out this diagnostic procedure anesthesia is required. Local anesthesia was selected for the aspiration procedure and the subsequent surgery. Bilateral mandibular injections utilizing an aspirating syringe with a disposable needle is being used. Note that aspiration before injection is being practiced and whenever the depth of the needle is changed, reaspiration before injection is carried out. Infiltration of the covering mucosa is utilized for hemostasis. Note that the syringe is turned so the glass carbure will be visible to the operator to facilitate visualization of any aspirated blood. After anesthesia is obtained a lower lock syringe with a 13 gauge needle is inserted into the substance of the mass. The needle is placed in several different areas of the mass and eventually an area is encountered that yields a small amount of thick yellowish white caseus material. The aspiration of this yellowish white thick caseus material establishes the fact that there is a sebaceous like substance in the central portion of the mass and points to an epidermoid inclusion cyst as the correct diagnosis. Following this tentative diagnosis surgical removal of the mass is indicated. Surgery in the floor of the mouth presents several problems. On either side of the midline are noted the openings of the submaxillary ducts and the surgery should not injure these important structures. Larger vessels and nerves must also be avoided. To expose a cystic mass a cautious incision is made to the mucosa in the midline being careful to avoid the submaxillary ducts. This incision is made carefully to avoid incision of the underlying capsule. Incision of the capsule would release the contents of the cyst into the wound and make the surgery more difficult. For complete access the incision is extended on to the ventral surface of the tongue. The dissection through the mucosa progresses carefully until the capsule of the underlying mass is completely exposed. Following incision of the mucosa the scapule is discarded and the mass separated from the surrounding connective tissue by blunt dissection. A small hemostat is utilized in this dissection. The floor of the mouth is a very vascular region and to avoid excessive hemorrhage the blunt dissection is carefully continued. Note the distinct capsule surrounding the mass and the distinct plane of separation that develops. As the superior and lateral aspects of the mass are freed it begins to protrude into the exposed area. To reach the depths of the mass a curved curette is used to free the fibrous attachments and as the dissection proceeds mobilization of the mass is evident. Movement of the mass from side to side facilitates access to the deeper areas. The dissection reaches a depth where use of the curette is no longer effective. The blunt dissection is carried deeper utilizing a small piece of gauze in a hemostat. As the mass becomes more mobile traction is applied with an Alice forceps. This permits access to the deeper attachments. These are separated by means of a blunt elevator. As the mass is delivered from the wound a few remaining bands of fibrous tissue are encountered attaching the mass on its inferior surface. These are sectioned with scissors after ascertaining that no large vessels are contained in the tissue. The remaining attachments in the depth of the wound are visualized and cut completely freeing the mass without rupture of the capsule. Maintaining the integrity of the capsule facilitates the surgery and prevents the contents of the mass from escaping into the operative wound. The excise mass is a large firm distinctly encapsulated lesion that offers firm resistance to compression. As it is compressed some of the thick material can be seen extruding from the opening in the capsule that resulted from the aspiration. The consistency of this material explains the difficulty that was encountered when the diagnostic aspiration procedure was carried out. The operative defect is examined carefully to ensure complete hemostasis and removal of all fibrous tissue tags. The wound is now ready for closure. Closure of the wound presents several problems. An operative defect of considerable size remains and this defect must be eliminated. The mass develop planes of separation. An extravasated blood and serum might occupy these planes to produce hematoma and thus delay healing. Since the mass has displaced muscle tissue, there is a tendency for the displaced muscles to return to their original position and assist in obliteration of the defect. To further collapse the wound, absorbable sutures are inserted in the deeper muscle layers. These deep sutures are placed in sufficient number to eliminate all dead space. Closure of the mucosa is a very important step. The suture is passed through the mucosal flap on the right side. It then passes through the muscle tissue deep in the wound, then through the mucosal flap on the left side. As this suture is tied, it anchors the mucosal flap to the underlying muscle and obliterates the space that otherwise might develop. Two or three sutures of this type anchor the mucosa in several areas. The remaining sutures are passed only through the mucosa to approximate the cut surfaces. Sutures are placed in sufficient number to ensure accurate re-approximation of the tissue. Immediate postoperative observation reveals normal mobility of the tongue. Pressure in the submetal area no longer causes a movement of the floor of the mouth. To discuss this case and to describe the pathology, we have enlisted the aid of an oral pathologist. Would you be kind enough to discuss this case and describe the lesion? This is a very interesting case, and most of the clinical possibilities have been discussed already. The only thing I can add to that list is the possibility of a brachial cleft cyst in the floor of the mouth. But let's look at the gross specimen now. The gross specimen is circumscribed and appears encapsulated. On palpation earlier it was slightly compressible. When the lesion is cut one can see that it reveals a cystic mass which is filled by thick cheesy material. The wall is quite thin. Grossly therefore it appears to be a cyst of some sort. The microscopic slide shows a collapsed cystic lesion which is lined by stratified squamous epithelium. The empty space in the center contains sebaceous material. The lining of the cystic lesion does not show any pseudo epithelium at its hyperplasia. The second slide reveals that the connective tissue wall of this lesion contains a number of small glandular structures which mimic the sebaceous glands of the skin. In one area a small keratin cyst or a sebaceous cyst can be seen. The presence of these sebaceous glands establishes this lesion as an epidermoid inclusion cyst. Would you discuss the relationship of a lesion of this type and a dermoid cyst? A dermoid cyst is really a teratoma. These lesions occur most frequently in the ovaries, in the testes, in the midline of the body and on rare occasion may arise in the floor of the mouth. Since the teratomas have unlimited growth potentiality, they should be classified as neoplasms. However, the lesion like the one we saw in this case is an epidermoid cyst. Thank you very much. It is well recognized that the final diagnosis of any surgical specimen depends upon the microscopic examination. The patient did well postoperatively. When seen 24 hours after surgery, there was little edema and no limitations of movement of the jaws. The patient had experienced little pain and only mild sedation was required. The wound is intact and appears to be healing by primary intention. Healing was entirely uneventful. When seen two months after surgery, complete healing of the operative wound was evident with no residual. The openings of the submaxillary ducts have not been disturbed. The movement of the tongue is now normal and the original complaints of difficulty in mastication and speech has been resolved. This case presents the problems associated with an epidermoid inclusion cyst in the floor of the mouth. Differential diagnosis of swellings of the floor of the mouth has been discussed. It is evident that diagnosis is not difficult when all the facts are mobilized prior to surgical intervention. When surgery is based on a sound diagnosis and the surgical procedures adhere to sound surgical principles, excellent results with minimal postoperative problems can be anticipated.