Quick Review for Patients

 
The lipoma is a benign tumor (neoplasm) of fatty tissue.  It may be moveable beneath the surface of the mouth membrane and more superficial lesions have a yellow/white color.  It is painless and slowly enlarges, sometimes to become several inches across.  It can occur at any age and will not diminish on its own, hence, must be surgically removed.  It has no potential for developing into a cancer.

 

 

 

Introduction

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The lipoma is a very common benign tumor of adipose tissue, but its presence in the oral and oropharyngeal region is relatively uncommon, with a prevalence rate on only 1/5,000 adults (Table 1). The first description of an oral lesion was provided in 1848 by Roux in a review of alveolar masses; he referred to it as a "yellow epulis." While most lesions are developmental anomalies, those which occur in the maxillofacial region usually arise late in life and are presumed to be neoplasms of adipocytes, occasionally associated with trauma. As with all fatty tissue, a lipoma will float on the surface of formalin rather than sink to the bottom of a biopsy specimen jar.

Clinical Features

The lipoma is a slowly enlarging, soft, smooth-surfaced mass of the submucosal tissues (Figures 1 & 2). When superficial, there is a yellow surface discoloration. When well-encapsulated, tumors are freely movable beneath the mucosa, but less well-demarcated lesions are not movable. The lesion may be pedunculated or sessile and occasional cases show surface bosselation. The tumor has a less dense and more uniform appearance than surrounding fibrovascular tissues when it is transilluminated. MRI scans are very useful in the clinical diagnosis; CT scans and ultrasound are less reliable.

Few oral or pharyngeal lesions occur before the third decade of life and there is no gender predilection. Once present, a mucosal oral lipoma may increase to 5-6 cm. over a period of years, but most cases are less than 3 cm. in greatest dimension at diagnosis. Rarely, a lipoma will occur within maxillary bones or sinuses, but usually this entity is found in the buccal, lingual or oral floor regions. Multiple head and neck lipomas have been observed in neurofibromatosis, Gardner syndrome, encephalocraniocutaneous lipomatosis, multiple familial lipomatosis, and Proteus syndrome. Generalized lipomatosis has been reported to contribute to unilateral facial enlargement in hemifacial hypertrophy.

Pathology and Differential Diagnosis

The lipoma is composed predominantly of mature adipocytes, possibly admixed with collagenic streaks, and is often well demarcated from the surrounding connective tissues (Figures 3 & 4). A thin fibrous capsule may be seen and a distinct lobular pattern may be present. Quite often, however, lesional fat cells are seen to "infiltrate" into surrounding tissues, perhaps producing long, thin extensions of fatty tissue radiating from the central tumor mass (Figure 5). When located within striated muscle this infiltrating variant is called intramuscular lipoma (infiltrating lipoma), but extensive involvement of a wide area of fibrovascular or stromal tissues might best be termed lipomatosis.

Occasional lesions exhibit excessive fibrosis between the fat cells (fibrolipoma), excess numbers of small vascular channels (angiolipoma), a myxoid background stroma (myxoid lipoma, myxolipoma), or areas with uniform spindle-shaped cells interspersed between normal adipocytes (spindle cell lipoma, Figure 6). When spindle cells appear somewhat dysplastic or mixed with pleomorphic giant cells with or without hyperchromatic, enlarged nuclei, the term pleomorphic lipoma is applied. When the spindled cells are of smooth muscle origin, the term myolipoma may be used, or angiomyolipoma when the smooth muscle appears to be derived from the walls of arterioles.

Rarely, chondroid or osseous metaplasia may be seen in a lipoma (osteolipoma, ossifying lipoma, chondroid lipoma, ossifying chondromyxoid lipoma). When bone marrow is present, the term myelolipoma is used. Also on rare occasions, isolated ductal or tubular adnexal structures are scattered throughout fat lobules, in which case the term adenolipoma is applied. Perineural lipoma has also been reported.

On occasion, lipoma of the buccal mucosa cannot be distinguished from a herniated buccal fat pad, except by the lack of a history of sudden onset after trauma. Otherwise, lipoma of the oral and pharyngeal region is not difficult to differentiate from other lesions, although spindle cell and pleomorphic types must be distinguished from liposarcoma. When metaplastic calcified tissue is present, the lesion may be confused with soft tissue chondroma or soft tissue osteoma.

The benign neoplasm of brown fat, hibernoma, has been reported in the oral/pharyngeal region only rarely. This childhood tumor is comprised of lobules of highly vascular stroma admixed with three types of adipocytes: a large, univacuolated fat cell with a peripheral nucleus; a moderate-sized multivacuolated fat cell with scanty granular, eosinophilic cytoplasm and a centrally located rounded nucleus; and a smaller cell with the same cytoplasm but with only small circular spaces representing fat microvacuoles.

A fat tumor comprised of a central core of mature adipocytes and a peripheral envelope of cells containing variably sized fat vacuoles is called lipoblastoma (Figure 7). Affected cells are smaller than normal, with 1-4 vacuoles, perhaps with a light, wispy cytoplasm between vacuoles. Some cells have nuclei centrally located, as seen in the moderately-sized cells of hibernoma, while others show the nucleus to be pushed toward the cytoplasmic membrane (signet-ring cell). Mitotic activity is extremely rare and fibrous septa separate fat lobules in this tumor. An abnormality of the long arm of chromosome 8q11-13 is a rather consistent finding in the lesional cells.

Treatment and Prognosis

Conservative surgical removal is the treatment of choice for oral lipoma, with occasional recurrences expected. An infiltrating lipoma often must be simply debulked, a portion of the infiltrating fat being deliberately allowed to remain in order to preserve as much normal tissue as possible.

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References (Chronologic Order)

Note: General references can be found by clicking on that topic to the left.

Roux M. On exostoses: there character. Am J Dent Sc 1848; 9:133-134.

Shear M. Lipoblastomatosis of the cheek. Br J Oral Surg 1967; 5:173-179.

de Visscher JGAM. Lipomas and fibrolipomas of the oral cavity. J Maxillofac Surg 1982; 10:177-181.

Rapidis AD. Lipoma of the oral cavity. Int J Oral Surg 1982; 11:263-275.

Chen SY, Fantasia JE, Miller AS. Myxoid lipoma of oral soft tissue: a clinical and ultrastructural study. Oral Surg Oral Med Oral Pathol 1984; 57:300-307.

McDaniel RK, Newland JR, Chiles DG. Intraoral spindle cell lipoma: case report with correlated light and electron microscopy. Oral Surg Oral Med Oral Pathol 1984; 57:52-57.

Guillou L, Dehon A, Charlin B, et al. Pleomorphic lipoma of the tongue: case report and literature review. J Otolaryngol 1986; 15:313-316.

Rigor VU, Goldstone SE, Jones J, et al. Hibernoma: a case report and discussion of a rare tumor. Cancer 1986; 57:2207-2211.

Macmillan ARG, Oliver AJ, Reade PC, et al. Regional macrodontia and regional bony enlargement associated with congenital infiltrating lipomatosis of the face presenting as unilateral facial hyperplasia. Int J Oral Maxillofac Surg 1990; 19:283-286.

Fujimura N, Enomoto S. Lipoma of the tongue with cartilaginous change: a case report and review of the literature. J Oral Maxillofac Surg 1992; 50:1015-1017.

Zelger BWH, Zelger BG, Plorer A, et al. Dermal spindle cell lipoma – plexiform and nodular variants. Histopathol 1995; 27:533-540.

Tallini G, Dalcin P, Rhoden KJ, et al. Expression of Hmgi-C and Hmgi (Y) in ordinary lipoma and atypical lipomatous tumors – immunohistochemical reactivity correlates with karyotypic alterations. Amer J Pathol 1997; 151:37-43.

Kang N, Ross D, Harrison D. Unilateral hypertrophy of the face associated with infiltrating lipomatosis. J Oral Maxillofac Surg 1998; 56:885-887.

Table 1: Gender-specific prevalence rates per 1,000 population for selected oral masses and surface alterations in U.S. adults, ranked by total frequency. Modified from Bouquot JE. Common oral lesions found during a mass screening examination. J Am Dent Assoc 1986; 112:50-57, and Bouquot JE, Gundlach KKH. Oral exophytic lesions in 23,616 white Americans over 35 years of age. Oral Surg Oral Med Oral Pathol 1986; 62:284-291.

Diagnosis

Number of lesions per 1,000 population*

Males

Females

Total

Leukoplakia

43.2

20.9

28.9

Torus palatinus 

13.2

21.7

18.7

Irritation fibroma

13.0

11.4

12.0

Fordyce granules

17.7

5.2

9.7
Torus mandibularis 9.6 7.9 8.5

Hemangioma

8.4

4.1

5.5
Erythema, inflammatory 4.5 4.8 4.7

Papilloma

5.3

4.2

4.6

Epulis fissuratum

3.5

4.4

4.1

Varicosities, lingual

3.5

3.4

3.5
Fissured tongue 3.5 3.1 3.2
Benign migratory glossitis 3.4 3.0 3.1
Aphthous ulcer 3.3 3.0 3.1

Papillary hyperplasia

1.7

3.8

3.0

Mucocele

1.9

2.6

2.5
Herpes labialis (herpes simplex) 2.4 2.6 2.5
Traumatic ulcer 2.1 2.1 2.1
Angular cheilitis 1.8 1.9 1.9
Smokeless tobacco keratosis 4.3 0.2 1.7
Hematoma or ecchymosis 2.0 1.4 1.6

Enlarged lingual tonsil

2.4

1.2

1.6
Chronic cheek bite 0.7 1.4 1.2

Lichen planus

1.2

1.1

1.1
Squamous cell carcinoma 2.5 0.1 0.9
Amalgam tattoo 0.6 1.0 0.9

Buccal exostosis

0.9

0.9

0.9
Leaf-shaped fibroma 0.4 1.2 0.9

Median rhomboid glossitis

0.8

0.5

0.6
Hairy tongue 1.2 0.3 0.6
Nicotine palatinus 1.2 0.2 0.6
Atrophic glossitis (smooth tongue) 0.6 0.5 0.6

Epidermoid cyst

0.7

0.4

0.5

Oral melanotic macule

0.5

0.3

0.4

Oral tonsils (except lingual)

0.5

0.3

0.4
Leukoedema 0.4 0.3 0.3

Lipoma

0.2

0.1

0.2

Ranula

0.2

0.1

0.2
Gingival hyperplasia 0.1 0.1 0.1

Buccinator node, hyperplastic

0.1

0.1

0.1

Pyogenic granuloma

0.0

0.07

0.04

Nasoalveolar cyst

0.0

0.07

0.04

Neurofibroma

0.0

0.07

0.04

* total examined population = 23,616 adults over 35 years of age 

 

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