COM October 2013 Diagnosis

Large & Completely Asymptomatic Swelling of the Posterior Tongue

Can you make the correct diagnosis?

This is a 58-year-old male who was completely unaware of a large swelling in the posterior tongue.

1. Ranula

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The most common location for a mucocele is by far the lower lip. In the area of the tongue and floor of mouth (FOM), ranulas are unlikely to occur in the posterior tongue. The anterior FOM and ventral tongue are the most common locations for a ranula/mucocele in this area. However, the soft consistency of the swelling suggests this condition. The histology in this case is not supportive of a ranula/mucocele.

Mucoceles and ranulas are clinical terms describing exophytic, fluid-filled, fluctuant nodules, typically of minor salivary gland origin and present mostly on the lower lip and the floor of mouth. Over 90% of these lesions are cyst-like structures, or pseudocysts, and are mucous extravasation phenomena referred to as mucoceles. Some of these lesions are true cystic structures lined by epithelium and filled with mucus and are called mucus retention cysts or salivary duct cysts. These constitute a small percentage of all mucoceles. Ranulas, mucoceles of the floor of mouth, constitute another 5% of these lesions. They are divided into types by location of occurrence: those above the mylohyoid muscle, which make up the majority of cases, and those below the mylohyoid muscle (also known as plunging ranulas or cervical ranulas). Ranulas are of minor or major salivary gland origin and are mostly extravasation in type. The etiology of extravasation mucoceles is usually sharp trauma cutting through the salivary gland duct and releasing the mucous in the extracellular tissue. Histologically, the extravasation-type mucocele consists of a cyst-like structure lined by granulation tissue and filled with mucoid material, foamy macrophages, and at times small clusters of neutrophils. The mucous retention cysts develop as a result of a duct blockage which can be caused by trauma, fibrosis, sialolith, or pressure from an overlying tumor. Extravasation mucoceles most commonly occur on the lower lip and very rarely on upper lip. They may occur anywhere else in the oral cavity, including the buccal mucosa and floor of mouth (Ranula). The latter can be of minor salivary gland or submandibular or sublingual gland duct origin and is more commonly seen in children and adolescents. It presents as a swelling with a bluish color if superficial, while deep mucoceles tend to take the color of the surrounding mucosa. Mucoceles tend to fluctuate in size. They are usually associated with a history of sharp lip or cheek biting, but can also be secondary to surgery in the area. This is especially true with the anterior tongue mucoceles. Surgical excision with the associated minor salivary gland is the preferred treatment for deep mucoceles; superficial mucoceles can self-heal within 2-3 weeks. Superficial mucoceles can also mimic vesiculobullous-type diseases because they look like vesicles, especially when presenting in multiples (an occurrence that is rare, but described in the literature). They can recur if the source of trauma is not eliminated or if they are secondary to surgery. Simple (non-plunging) ranula is best treated by marsupialization into the floor of mouth. Plunging ranula requires complete excision via an extra-oral approach. The technical difficulties associated with the complete removal of this thin-walled lesion result in a relatively high recurrence rate.

2. Dermoid Cyst

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The location and the age of the patient are not consistent with a dermoid cyst. The region is, as is the slow growth and asymptomatic clinical presentation. The histology is not consistent with a dermoid cyst.

Dermoid cysts of the oral cavity are rare and constitute around 1.6% of all dermoid cysts, according to the original 1937 report on this condition by New and Erich. They are more common in the testes than in any other location, followed by the ovaries and the head and neck area. In the latter area, the floor of mouth is one of the more common areas of occurrence. This cyst is clinically classified into three types and is based on its relationship to the floor of mouth muscle and the geniohyoid and mylohyoid muscles. The more common presentation is above the geniohyoid and mylohyoid muscles, which are clinically visible in the floor of mouth as they push the tongue upward, leading to dysphagea, dyspnea and dysphonia. If it is between the geniohyoid and the mylohyoid muscle or below the mylohyoid muscle, it can create the appearance of a double chin. The third type is that in which the cyst is displaced laterally into the submandibular area. Dermoid cysts of floor of the mouth are rarely described in children under the age of 10. The majority of cases in the floor of mouth occur between the ages of 10 and 30; in cases in the ovaries, the age range is 15 to 40. Dermoid cysts above the geniohyoid muscle present as slowly enlarging large, round, raised and smooth-surfaced nodules. The nodule is usually painless unless it is infected. Infected cysts can drain through either intraoral or extraoral fistulas. The size of the lesion determines its interference with eating, speaking and swallowing. This cyst is classified histologically into two types: cystic structures with a lumen filled with keratin and a connective tissue wall with skin adnexa and true cystic teratomas with all three germ layers tissues such as the brain, bone, muscle, respiratory and gastrointestinal tissues. The oral dermoid cysts tend to be simple with skin adnexa in the wall. The true teratoma type cysts (more common in the ovary) are prone to malignant transformation more so than those in the floor of mouth. Treatment of choice is surgical removal via intra or extra oral approach, depending on where the cyst is located.

3. Thyroglossal Duct Cyst

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The location, the slow growth, and the asymptomatic presence of this swelling are all common clinical presentations of the thyroglossal duct cyst. The age of the patient and the soft consistency of the swelling is not consistent with this condition; neither is the histology.

Thyroglossal duct cyst is an uncommon cyst. It arises along the embryonal thyroglossal tract, which is between the foramen cecum in the posterior tongue and the thyroid gland. Up to 80% occur below the hyoid bone. This cyst presents at any age, but is more common in young individuals; 50% occur in patients under 20 years of age. It is usually a firm, cystic mass in the midline. It is of variable size. It is usually asymptomatic and slow growing, but dysphagia may occur if it occurs in the higher portion of the tract. A fistula may also develop if it gets infected. It has a characteristic histological presentation of a cystic cavity lined by epithelium and supported by a connective tissue wall containing mucous secreting glands, thyroid follicles, benign lymphoid aggregates and others. Complete surgical removal is the treatment of choice; however, given the difficulty of removing the tract the lesion may recur and complete removal may be a challenge. The overall prognosis is good. The likelihood of recurrence depends on the completeness of removal. Squamous cell carcinoma within the lining epithelium has been described.

4. Lipoma

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The age and gender of this patient are typical for those of patients with lipoma of the mouth. The clinical description of soft consistency is also typical of a lipoma, as is the slow growth and the asymptomatic clinical presentation. The histology is consistent with that of a benign lipoma.

Lipomas are benign neoplasms of adipose tissue origin. They are more commonly described in the trunk and extremities and are rare in the oral cavity. Their overall incidence in the oral cavity accounts for around 4.4% of all benign oral lesions. In a recent study from the Armed Forces Institute of Pathology (AFIP) of 125 benign lipomas in and around the mouth, the male to female ratio was approximately 3:1, which is not surprising given the study was conducted within a military population. Other studies reveal an equal gender distribution. The AFIP study showed the mean age to be 52 with a range of 9-92 years. Only 4 of the 125 cases involved patients under 18. In the mouth, the most common location for this neoplasm is the buccal mucosa followed by the lips, submandibular area, tongue, palate and, less often, in the floor of mouth and vestibule. These findings are consistent with many other published reports. These lesions are slow-growing and can be present for many years. Lipomatous nodule of the buccal mucosa may represent herniation of the buccal fat pad. Lipomas usually present as a single, smooth surfaced, soft with doughy consistency, lobulated, painless, yellowish, sessile nodule. The overlying mucosa is usually thin and stretched with visible blood vessels. Because of its softness it can be mistaken for a cyst. Histologically, lipomas are variable benign histologies. Some have predominant lobules of mature adipocytes surrounded by a thin connective tissue capsule, while others have a predominant spindle-cell component, myxoid, chondroid, or connective tissue component. Some are intramuscular. Each has its own clinical behavior. Simple surgical excision is the treatment of choice for the simple, mature adipocyte component.

References

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