Ⅰ. INTRODUCTION

Lipoma is a common soft tissue tumor, accounting for 50% of all soft tissue neoplasm, however, rare in the oral cavity. [5, 7] Ordinary lipoma is a most common neoplasm of mesenchymal origin. [8] Lipoma is a benign tumor of adipocytes that can be found in almost any part of the body, accounting for 4~5% of all benign tumors. [9] It appears a lobular growth of mature adipocytes with well-demarcated, most commonly occurs in subcutaneous tissue. [7] Only 13% of all lipoma occurs in the head and neck, most of them occur in the subcutaneous layer of posterior neck. [8] Rarely, lipomas can appear in the anterior neck, infratemporal fossa, oral cavity, pharynx, larynx, and parotid gland. [8] Oral lipoma is rare in oral cavity, and accounts for approximately 1 to 5% of all benign neoplasm in the mouth. [7]

Ⅱ. CASE REPORT

A 71-year-old male presented with complaints of mastication and conversation due to multiple tongue swelling. On the physical examination, asymptomatic swelling on the right and left side of the tongue which started 2 weeks ago. The patient has hypertension and alcoholic liver cirrhosis for one year. On the clinical examination, multiple soft and roundshape swellings were detected with thin mucosa, and were located on the lateral side of tongue. The size of the lesion was about 3cm in diameter on the right side of tongue, and other two small lesions were observed on the left side. (Fig. 1) There was no history of oral trauma. Magnetic resonance imaging (MRI) showed about 2.3x2.7x2.8cm sized mass on upper margin of the right tongue, and about 1.1x1.2cm sized mass on the upper margin of left tongue with T1, T2 welldefined high signal intensity. Lesions were not enhanced, and right midline septum was displaced to the left due to right tongue mass. However, invasion or destruction of the lesions were not observed. (Fig. 2, 3) The mass has surgically resected under general anesthesia. A total of three tongue lipomas were removed. All of them were yellowish and relatively well encapsulated with surrounding tissues. The size of lesions was about 3x2cm, 1.5x1.5cm, 1x1cm. (Fig. 4) The bleeding site was controlled using bovie coagulator and hemostatic agent (Surgicel, Johnson and Johnson, 1/2 in x 2 in) and suture was performed on the muscle and mucosal layer using 4-0 vicryl (Ethicon). The specimen shows mature white adipose tissue without atypia. The size of the adipose tissue is twice to five times larger than that of the normal adipose tissue, with obvious large cells up to 300 microns. Cytoplasmic vacuoles are relatively uniform. (Fig. 5)

Ⅲ. DISCUSSION

Lipoma is a slowly growing benign neoplasm and is composed of mature adipocytes. [1] Lipoma is the most common mesenchymal tumor of soft tissue. [2] Lipoma is a relatively rare in the oral and maxillofacial regions,[1] Prevalance rate of lipoma in the oral and oropharyngeal region is 1/5000 adults. [10] However among them, the most common site is buccal mucosa, rich in adipose tissue, followed by the tongue. [1] [2] In several reports, oral lipoma account for about 1 to 4% of all neoplasms. [2-5] Other literature reports that oral lipoma account for 2.2% of all lipoma and 2.4% of all benign tumors in the mouth. [1] In another document, lingual lipoma account for 0.3% of the tumors on the tongue, because of the absence of adipose cell in the tongue. [11]

The etiology of lipomas remains unclear. Some factors could be related to the pathogenesis: trauma, chromosomal abnormality, hereditary, chronic irritation, hormonal imbalance and metabolic conditions. [12]

Esther Manor et al. (2011) [5] and E.R. Fregnani et al. (2003) [3] reported that oral lipomas occur without gender predilection. Mary A. However, Furlong et al. (2004) reported that oral lipoma has male predominance. [4]

Oral lipomas occur mainly in adults between 40 to 60 years of age. [4, 13] Mary A. Furlong et al. (2004) reported that 4 of 125 oral and maxillofacial lipomas happen under the age of 18, [4] and Esther Manor et al. (2011) reported that 1 of the 58 patients of oral lipoma occur younger than 18 years of age. [5] Also, a study of 46 patients by E.R. Fregnani reported that lipoma show predominance in adults. [3]

The clinical features of lipomas vary according to their growth rate, size, and location. In general, it shows painless, palpable mass, and a rare dysfunction or sensory disturbance of when invading muscle or pressing on the branch of the trigeminal nerve. [1, 13] Tongue lipomas are more susceptible to clinical suspicion when the thin mucosa with yellow and elastic consistency has observed. [11]

The treatment of lipomas is a simple surgical excision. For some authors, they must be excised with surrounding normal tissue to prevent recurrences. [14] Occasionally, adipose tissue can invade muscle, and in the case of intramuscular (infiltrating) lipomas, muscle dysfunction or sensory changes may rarely occur due to pressure on nerve trunk. [1, 2] In the case of intramuscular lipoma, recurrence tends to occur after resection due to the difficulty of complete resection, and local recurrence rate range from 60 to 62.5%. [1] [11] Patient in this case was followed for 3 months after mass removal, and there was no signs of recurrence during that period.

Ⅳ. CONCLUSION

In conclusion, oral lipoma is not common, but it has clinical characteristics are relatively easy to detect. It commonly present as a soft, mobile, lobulated, and yellow soft tissue mass. [13] In most cases, lipoma is encapsulated which is easy to remove. However intramuscular lipoma has been reported high recurrence rate. This is a report of multiple lipomas on the tongue which is not previously reported.