Unusual presentation of lipoma on the tongue

Abstract

Lipomas are benign soft tissue neoplasm which rarely occur in the oral cavity. Of the total reported cases of lipoma, only about 15% to 20% of cases have occurred in the head and neck region and the tongue is an even rarer site with only about 4% of the reported cases occurring in that region. They are slow growing and usually asymptomatic in nature. When it grows to a large size, it can hinder the physiological processes that are associated with the area. This case report describes the diagnostic features of tongue lipoma with a brief review of literature.

Background

Lipomas are one of the most common benign tumour of mesenchymal origin in human body. It is composed of mature adipose tissue. Intraoral lipomas can occur anywhere in the oral cavity including the buccal mucosa (37.9%), tongue (24.2%), lip (10.5%), palate (7.4%), floor of the mouth (7.4%), vestibule (6.3%), retromolar area (4.2%) and gingiva (2.1%).¹ Lipoma occurring in the tongue is rare as tongue contains less amount of fat tissue. It primarily affects middle-aged individuals and may slowly enlarge causing difficulties in speech and mastication.² Generally they are non-invasive and have a low recurrence rate except for the intramuscular variant. Recurrence rate is low and conservative surgical management is the treatment of choice.³ Present case is unique because of its presentation in an unusual site with uncharacteristic clinical presentation. Even though the patient was asymptomatic, removal of the lesion could add more comfort to the patient especially for functional activities.

Case presentation

A 56-year-old female patient came to the Department of Oral Medicine and Radiology with the chief complaint of pain in the upper right back tooth region since past 2 days, which was throbbing, localised and intermittent. It aggravated on chewing and on lying down and gets relieved by its own after some time. Medical and family history were unremarkable. No abnormalities were detected on extra oral examination. On intraoral soft tissue examination, a growth was noted on the dorsal surface of the tongue at the junction of anterior two-third and posterior one-third, midway between the midline of the tongue and left lateral border (figure 1). Further history regarding the growth revealed that the growth was present since she could remember and it grew to its present size gradually, without any pain or pus discharge. No history of trauma, difficulty in swallowing or chewing was reported. Further examination of the site revealed a pedunculated growth with a large base and keratosis on the superior aspect. Size of the swelling was approximately 1 cm in diameter. On palpation, it was non-tender, non-compressible, non-fluctuant, firm in consistency and slip sign was negative. Hard tissue examination revealed deep occlusal caries in relation to 16 and 17, which were non-tender on percussion.

Figure 1.

Intraoral view showing the growth on the dorsal aspect of the tongue.

Investigations

An intraoral periapical radiograph was advised for evaluation of periapical area in relation to 16 and 17.

Excisional biopsy of the growth on the dorsal surface of the tongue was advised.

Differential diagnosis

Based on the clinical findings a clinical differential diagnosis of neurofibroma and fibroma was given to the growth on the dorsal surface of the tongue.

Treatment

An excisional biopsy was carried out and the specimen was given for histopathological examination. Following the radiographic assessment, the chief complaint of the patient was duly taken care off.

Outcome and follow-up

The growth was sectioned in two halves and viewed under the microscope. It showed a well circumscribed and pedunculated lesional tissue which consisted of lobules of adipocytes separated by fibrous connective tissue septae. It was surrounded by superficial stratified squamous parakeratinised epithelium and a thin band of collagenous connective tissue stroma. It consisted of parallelly arranged bundles of collagen fibres surrounding the lesional tissue forming a capsule. Numerous blood vessels of varying sizes and normal muscle fibres were also noticed at the base of the lesion (figures 2 and 3).

Figure 2.

Histopathological section showing capsule of the lipoma.

Figure 3.

Histopathological section showing adipocytes and connective tissue.

A final diagnosis of lipoma on the dorsal surface of the tongue was given after the histopathological examination.

Patient reported a week after the surgical excision and reported that she is feeling better while talking and swallowing food. Wound healing was uneventful and patient is under regular follow-up (figures 4 and 5).

Figure 4.

Follow-up photograph after 1 week post excision.

Figure 5.

Follow-up photograph taken 1 month post excision.

Discussion

Lipomas are benign tumours of the adipose mesenchyme and are uncommon in the oral cavity.⁴ They are the most common mesenchymal tumour of the human body.⁵ They represent only about 1% to 4% of the benign tumours of the oral cavity. It was initially described as a yellow epulis by Roux in 1848. First case of an intraosseous lipoma (IOL) was reported by Cornil and Ranvier in 1880. IOL of mandible was first reported by Oringer.³

Aetiology and pathogenesis of lipomas is still unclear. Earlier views of aetiology of lipomas reported that it arised from the lipoblasts and the proliferating embryonic mesoderm. It may arise due to fatty degeneration of other cells or due to metaplasia of muscle cells. Hypertrophy theory states that obesity and additional deposition of adipose tissue can result in the formation of oral lipomas. But it is not well accepted as its behaviour is not related to whole body metabolism and calorie intake. Another theory for the formation of lipoma is metaplasia theory which states that lipoblast formation may occur due to abnormal differentiation of mesenchymal cells. Trauma, hormonal influence, chromosomal abnormalities and chronic irritation may play role in the differentiation of the dormant cells into fat cells.⁵ It is proposed that after soft tissue injury and subsequent haematoma formation, cytokines involved in the repair process trigger the adipocyte differentiation and proliferation.⁶

Lipomas are commonly seen in fifth to sixth decade of life but rare cases of congenital lipomas have also been reported.⁵ The lesion in our case may be considered as congenital because patient reported that it was present on the tongue as long as she could remember. They do not have a specific gender predilection although the extra oral lipomas have a preference for women above 40 years.⁴ The most common site for an intraoral lipoma is the buccal mucosa, which is rich in fatty tissue followed by the tongue, lips and floor of mouth. Lipoma occurring on the tongue is considered to be rare as it is predominantly a mucomuscular organ. These tumours are slow growing in nature, sessile, painless and present as well circumscribed nodules that grow for a long period of time.³ Rarely it may appear pedunculated or submerged.⁷ It may present with a yellowish hue and is usually asymptomatic. Size may range from 0.2 cm to 50 mm. On palpation it is non-tender, soft or cheesy in consistency. Large lipomas may present with functional difficulties like difficulty in speech, mastication, etc.

Conventional lipoma arises from the subcutaneous tissue and appears as a superficial lesion. Deep seated subtype may develop within the skeletal muscle and is known as intramuscular (infiltrating) lipoma. It will be diffuse and will produce only slight elevation. It is an uncommon variant and represents only less than 1% of all the lipomas.⁸ It is usually single but multiple lipomas may be seen in association with syndromes like Gardner’s syndrome, Proteus syndrome, Pai syndrome and neurofibromatosis.⁵

It may be seen as intraosseous tumours also rarely in the mandible. Bone lesions are usually incidental findings and are seen as unilocular or multilocular lesions with honey comb or soap bubble appearance with a sclerotic border. There are three stages in the development of an IOL. Stage 1 corresponds to lesions with no secondary necrosis, stage 2 is lesion with partial necrosis and stage 3 is lesions with complete secondary necrosis.³

Differential diagnosis of a lipoma of the tongue include haemangioma, lymphangioma, rhabdomyoma, neuroma or neurofibroma.⁵ Differentiation is easy if the surface epithelium is thin and the yellowish hue can be appreciated.² Neurofibroma is one of the most common lesions that occurs on the tongue. It can either occur as a solitary lesion or may present as multiple lesions when associated with a syndrome. Unencapsulated neurofibromas can show a similar appearance of a lipoma and they are also slow growing and painless, although paraesthesia might occur from tumour compression. It can also occur separately from syndromes with neurofibromatosis, without presence of café au lait spots, macules or skeletal abnormalities. Fibroma was considered, due to slow growing nature, presence of keratosis and firm consistency, although a negative aspect is the absence of any history of trauma to the region.⁷ Haemangioma and lymphangioma can mimic a lipoma of the tongue. They are congenital in nature. Haemangioma occurs most commonly on the lip followed by tongue. They are reddish or bluish lesions and compression will usually produce blanching of these lesions due to ischaemia. Lymphangioma most commonly occurs on the anterior two-third and central portion of the tongue and usually presents as a purplish mass. It can cause difficulty in swallowing and phonation due to its size. Fine needle aspiration can be done to rule out haemangioma and lymphangioma from a lipoma, as lipoma is a solid tumour and will not yield any aspirate.^{1 2} Rhabdomyomas are rare tumours of skeletal muscle origin. They are broadly classified into cardiac and extracardiac rhabdomyomas. Extracardiac rhabdomyomas are thought to originate from the muscle component of the third and fourth branchial arches. Their occurrence is mainly seen in the head and neck region, particularly on the floor of the mouth and the tongue. Diagnosis of this lesion is solely based on its distinctive histopathological and immunohistochemistry findings such as presence of large muscle bundles composed of ovoid or polygonal cells and positive staining with desmin or myoglobin.⁹

Imaging is not an essential part of the investigative battery of lipoma. If large or submerged ultrasonography can be used for the detection of lipoma of the tongue as it is cheaper, more readily available and non-invasive. On ultrasonographic examination, these tumours are lower in reflectivity than the adjacent muscle and more reflective than the subcutaneous fat. They appear hyperechoic and in some cases, they can also appear hypoechoic or isoechoic.¹⁰ MRI which, apart from suggesting a diagnosis of lipoma, shows accurately the boundaries of the tumour, the vascularity and proximity to critical anatomical structures.¹¹ They play an important role in the diagnosis of intramuscular lipomas which are difficult to diagnose by clinical examination alone. CT can be used for intraosseous lesions which may show a low mass density ranging from −60 to −120 Hounsfield units which is consistent with fatty tissue.⁸

Incisional biopsy is advised when the lesion is large and excisional biopsy is advised if the lesion is small, or like in this case, a pedunculated growth which could easily be excised.³ Histopathology is the gold standard for the diagnosis. The tumour is composed of adult fat cells that are subdivided into lobules by fibrous connective tissue septa.¹ Tumour vasculature consists of capillaries which are compressed by the surrounding adipocytes.⁸ They tend to float when kept in 10% formaldehyde solution.¹² Oral lipomas are classified histologically into chondrolipoma, spindle cell lipoma, myxolipoma, pleomorphic lipoma, angiolipoma, fibrolipoma, neurofibrolipoma, osteolipoma, sialolipoma and intramuscular lipoma or infiltrating lipoma depending on the predominant tissue present.² Oral intramuscular lipoma tend to occur on tongue due to its close association between adipose tissue and muscle fibres. They tend to infiltrate deep into the connective tissue spaces and may involve nerves, fascia, bones and joint capsules. Liposarcoma may resemble infiltrating lipoma histologically, but can be ruled out on the absence of cellular pleomorphism, nuclear hyperchromatism and low mitotic activity.¹ Presence of lipoblast is a characteristic feature of liposarcoma and is not present on lipoma⁸

The most effective treatment of a lipoma is surgical excision. Early management of lipomas are required as the tumour can assume large sizes and may cause difficulties in the physiological processes like speech, mastication and deglutition. It can also cause dental abnormalities like anterior open bite as well as airway difficulties, atrophy of tongue and macroglossia.² In cases of well encapsulated lipomas it is advisable to excise the lesion completely with an area of normal tissue to prevent recurrence.⁸ Diode laser can also be used as a surgical modality for oral lipomas. Relatively bloodless surgery, instant disinfection of the surgical wound along with reduced postoperative complications are its advantages. It is usually used in a wavelengths of 810, 940 and 980 nm for surgical excisions.¹³ Other methods of treatment include intralesional steroid injections, where the primary steroid of choice is triamcinolone acetonide and it is used in volumes varying from 1 to 3 mL depending on the size of the tumour. It works on the atrophication of the adipose tissue on tumours which is less than 1 inch in diameter. It also enables in avoiding a surgical scar.⁵

No recurrence has been reported for conventional oral lipomas after surgical excision.⁵ Intramuscular lipomas have a higher tendency to recur due to its infiltrative growth pattern. In cases of infiltrating lipomas, a recurrence rate of 3% to 62.5% has been reported.¹⁴

Patient’s perspective.

Even though I didn’t have any difficulty during my functional activities, I am glad that it was taken out and am feeling much better while talking and swallowing food.

Learning points.

• Intraoral lipomas, even though rare should be considered in the differential diagnosis of soft tissue swellings of the oral cavity.

• Lipomas can be long-standing and may present with unusual characteristic features as described above. Long-standing lipomas can undergo fibrosis and clinically mimic fibromas.

• When the lesion is long-standing, the patient may not find any interferences in the physiological processes from such lesions and hence, may not seek treatment. Patient can feel the difference only after the treatment as reported in the present case.

• Histopathology is the gold standard in the diagnosis and liposarcoma has to be ruled out as it appears similar to intramuscular type of lipoma.

• Conservative surgical management is the treatment of choice as the recurrence rate is rare, but intramuscular variant has to be treated with caution as it is infiltrating and may recur.